CIHEAM- Mediterranean
Agronomic Institute of Bari
Biological Control of Insect
Pests
Prepared by: Hamid El Bilali
and Vito Simeone
Contents
 Main non-pesticides control tools: micro-organisms, macro-
organisms, natural products and semiochemicals;
 Definition of biological control;
 Biocontrol history;
 Basic biological control theories;
 Biological control objectives;
 Biocontrol approaches;
 Biological control agents: parasitoids, predators and pathogens.
Pests control in organic
agriculture
In organic agriculture, crops protection is based first of all
on a good deal of knowledge on agroecosystem (biocenocis
and biotope) and information about the target pest,
prevention, interactions plant- environment-pest and finally
on the use of the allowed pesticides (Annex II-B of the
E.C.R. N° 2092/91).
Pests management
 Knowledge of the pest: key pest, identification, bio-ethology
and techniques of monitoring and sampling.
 Monitoring: Pheromone/chromotropic traps, sticky barriers…
 Prevention techniques.
 Biological control.
 Cultural management:
Appropriate species and varieties:
tolerant or resistant cultivars;
 Appropriate rotation programmes;
 Longer fallow period and more frequent grass rotation.
 Irrigation and fertilisation;
 Pruning, leaves removal…
 Mechanical practices: Use of mechanical
barriers- insect-proof net; floating row covers;
plastic tunnels, reflective mulches (aphids)…
 Use of authorised bio-pesticides.
Mechanical barrier against Otiorrhynchus cribricollis
Prevention techniques
 Site selection (climate and soil): Effective for nematodes and
soilborne pathogens ( Armillaria, Fusarium, Plasmodiophora,
Sclerotium, Verticillium, Phytophtora, Pythium and Rhizoctonia).
 Use of healthy material: Certified seeds (pathogen-free seeds) and
propagation material (transplants).
 Use of forecasting model can help in the management of some
diseases like fungal ones.
 Inoculum reduction:
 Crop rotations;
 Soil solarisation;
 Preventing the introduction of the inoculum by exclusion practices;
 Use clean pots, trays and potting mix;
 Inoculum eradication;
 Soil tillage….
Prevention techniques
 Use of resistant varieties and root-stocks;
 Shifting the cropping period: Coordinate planting and harvesting
dates to avoid pests.
 Field sanitation (roguing): Removal and destruction of diseased,
dying and dead plants;
 Promoting crops aeration by canopy management practices:
Effective against fungal diseases.
 Rational fertilisation (balanced in nitrogen) and irrigation
(clean water at proper amount);
 Promoting beneficial insects.
 Use of indicator plants: Rose for grapevine powdery mildew.
Pests biological control
 Release of reared beneficial predator and parasitoid
arthropod, insects and mites, (inoculative, augmentative or
inundative releases): Psyttalia (Opius) concolor against olive
fruit fly, Bactrocera oleae.
 Mating disruption.
 Use of antagonist micro-organisms: bacteria, Bacillus
thuringiensis against Lepidoptera, fungi Ampelomyces
quisqualis against powdery mildew; Protozoa; nematodes;
baculovirus and granulosis virus.
 Biological control of powdery mildew with: Orthotydeus
lambi (Tydeidae mite), Bacillus (subtilis) sp., Trichoderma
harzianum , Verticillium lecanii, Tilletiopsis sp. …
Pests biological control
Trap plants: Phacelia tanacetifolia againt Frankliniella
occidentalis, Tagetes sp. against nematodes (Meloidogyne spp.).
Oilseed radish could be a potential trap crop for cyst nematode
( Heterodera spp.).
Phacelia tanacetifolia
Bio-pesticides
 Advantages:
 Low mammalian toxicity;
 Minimal effect on beneficial insects;
 Fast action and breakdown so low environmental impact;
 High selectivity;
 Short pre-harvest interval;
 Low phytotoxicity.
 Limit: Contact products so adequate coverage is
essential to have a good efficacy.
 Types:
 Naturally occurring substances;
 Substances of plant origin (botanicals);
 Substances of animal origin;
 Microorganisms-based bio-pesticides.
Types of bio-pesticides
 Naturally occurring substances: Sulphur and lime sulphur
(calcium polysulphide), copper (up to 6kg/ha/year); quartz sand..
 Botanicals (plant origin): Azadirachtin (Azadirachta indica),
rotenone (Derris spp., Tephrosia spp. and Lonchocarpus spp. ),
pyrethrins (Chrysanthemum/ Tanacetum spp), Quassia amara
extract, Nicotiana tabacum extract, Sabadilla (Schoenocaulon
spp.), Hellebore (Veratum album), croton (Croton tiglium), Yam
bean (Pachyrhizus erosus ), Ryania (Ryania speciosa), thunder
god vine (Tripterygium wilfordii), Amur corktree (Phellodendron
amurense), Heliopsis longipes..
Types of bio-pesticides
 Plants oils: Mint, pine and caraway (Carum carvi ) linseed,
hempseed, cottonseed, rapeseed (colza), castor bean (Ricinus
communis), coconut, soybean, palm, corn...
 Substances of animal origin: beeswax, gelatine,
hyrolysed proteins…
 Animal fats: Whale, fish (cod, herring, menhaden, sardine),
degras (wool grease), lard, neatsfoot…
 Substances used in traps and/or dispensers:
Diammonium phosphate, metaldehyde, pheromones, pyrethroids
(Deltamethrin and Lambda-Cyhalothrin)
 Others: Paraffin and mineral oils, K-permanganate...
Pests biological control
 Use plant suppressive effects on diseases: Broccoli on
Verticillium dahliae microsclerotia, cover crops like mustards and
sudangrass on soilborne pathogens.
 Bio-fumigation: Use of compost and organic amendments
(castor, neem and argan cakes) supressive properties due to their
content in allelopathic substances to kill soil pathogens (nematodes
and soil-borne pathogens).
Non-pesticides control
In “The Manual of Biocontrol Agents” (Copping, 2004)
there are 373 entries of which:
 Micro-organisms: 112 entries (species/ isolates/
formulations).
 Macro-organisms: 126 entries (insects and mites,
arthropods);
 Natural products: 57 entries (microorganism- and plantderived products).
 Semiochemicals: 55 entries (sex, aggregation, and alarm
pheromones);
 Genes: 19 entries (resistance to hrerbicides, insects, and
viruses inducers).
Non-pesticides control
Semio-chemicals
15%
Genes
5%
Macro-organisms
34%
Micro-organisms
30%
Natural products
16%
(Copping, 2004)
Natural products especially
plant- and microorganismsderived ones
Natural products use in biocontrol
Algae, 1
2%
Crustaceans,
1
2%
Microorganisms, 20
34%
Plants, 36
62%
(Copping, 2004)
Natural products use in biocontrol
Plant growth
regulator and
nematicide, 2
3%
Others, 13
23%
Bactericide, 2
3%
Fungicide, insect
attractant and
animal reppelent; 9
15%
Fungicide and
bactericide, 2
3%
Insect reppelent, 5
8%
Plant growth
regulator, 6
10%
Insecticide and
acaricide, 8
14%
(Copping, 2004)
Insecticide, 12
21%
Azadirachtin
 Source: Neem tree, Azadirachta indica ;
 Family: Meliacae;
Natural Habitat : South Asia, in particular India ;
 Extracted from seeds (Kernels);
Azadirachtin: active ingredients
 Principal active ingredients: Azadirachtin A (AZA)
(C35H44O16) with its 7 isomers and Azadirachtin B ;
 Mechanism of action: repellent,
growth regulator, anti-oviposition,
reduces adults fecundity and
eggs vitality.
 Mode of action: Contact, ingestion with a systemic
activity;
 Activity spectrum: Effective against at lesat 200 insect
species, nematicide, acaricide with a certain fungicidal
activity.
 Pre-harvest interval: 3 days;
Rotenone
 Plants : Derris elliptica , mistica and malaccensis;
 Lonchocarpus utilis, urucu, nicou and chrysophyllus;
 Tephrosia macropoda, toxicaria, vogelii and virginiana;
 Family: Leguminosae;
 Extracted from roots;
Derris elliptica
Lonchocarpus sp.
Rotenone
 Principal active ingredients: Rotenone or Nicouline
(Isoflavonoid, Alkaloid) ;
Mechanism of action: Interference with respiration and with
perpherical nervous system;
Mode of action: Mainly by contact and sometimes via
ingestion;
Activity spectrum: Non-systemic selective insecticide
(Diptera, Coleoptera, Lepidoptera, Hemiptera,
Thysanoptera, Hymenoptera) with a secondary acaricidal
activity.
 Pre-harvest interval: 10 days;
Pyrethrins
 Plant: Tanacetum (Chrysanthemum)
cinerariaefolium and T. cineum.
 Family: Compositae;
 Natural habitat: China, east of Africa and Japan;
 Extracted from flowers;
 Main active ingredient: Pyrethrin I;
 Mode of action: Contact and ingestion;
 Mechanism of action: Acts on peripherical and central
nervous system causing an immediate insects paralysis;
Activity spectrum: mainly an insecticide with a certain
acaricidal activity;
 Pre-harvest interval: 2 days;
Pyrethrins: Active ingredients
There are six different active ingredients (pyrethrins) resulting from the
combination of two acids and 3 alcohols
Cathegory Acid
Pyrethrins Pyrethrins I
Alcohol
Crysanthe- Pyrethrolone
mic
Cinerolone
Pyrethrins II Pyrethroic
Active
ingredients
Pyrethrin I
Cinerin I
Jasmolone
Jasmolin I
Pyrethrolone
Pyrethrin II
Cinerolone
Cinerin II
Jasmolone
Jasmolin II
Semiochemicals: Reppelents,
attractants and sex, alarm, and
aggregation pheromones.
Semiochemicals use in biocontrol
Aggregation
pherom one, 1/
25%
Alarm
pherom one, 1/
2%
Sex pherom one,
39/
69%
Reppelent, 1/
2%
(Copping, 2004)
Attractant,1/
2%
Semiochemicals
 Sex pheromone:
Males locate and subsequently mate with females by following the
trail or pheromone emitted by virgin females.
 The indiscriminate application of high levels of sex pheromone in
traps and dispensers interferes with this natural process since a
constant exposure to high levels of pheromone makes trail following
impossible (habituation/adaptation phenomenon).
 The use of discrete source of sex pheromone released over time
presents the male a false trail to follow (sexual confusion/ mating
disruption).
 Control is subsequently achieved through the prevention of mating
and consequently the laying of fertile eggs.
 Sex pheromone are species-specific.
Semiochemicals
 Aggregation pheromones:
 Males and females locate host trees by following a plume of air
enriched with a mixture of the odour of the host tree and the
aggregation pheromone.
 Evaporation of pheromone vapours from dispensers attached to host
trees attract both males and females of the insect pest to the baited trees
and establiches conditions for mass attack of baited trees by the insect
pests.
 The baiting of selected areas and trees reduces the number of attacks
in the main orchard or forest areas.
 The baited trees and those trees closed to them should be felled
before the progeny emerges from the infested trees.
 Aggregation pheromone can be also used in monitoring.
 They are effective in the case of beetles (Coleoptera).
 Attractants are used in traps for monitoring and time management
decisions of pesticides applications.
Semiochemicals
 Alarm pheromones:
 Alarm pheromones are released under natural conditions when the
population in threatened or being attacked by a predator.
 The result of this release in an increase in the activity of
phytophagous insects with the subsequent higher exposure to a coapplied pesticide.
 Alarm pheromones are often mixed with conventional pesticides
(especially acaricide) and show an increase in the mortality of pests
(mites).
 The alarmed pests (e.g. spider mites) feed less than undisturbed
ones.
Semiochemicals
 Reppelent pheromones:
 Reppelent pheromones are emitted naturally by some insect pests
(e.g. beetles) when they reach a critical density in order to repel
additional insects and, thereby to protect the food supply needed by
these insects and their offspring.
 A slight chemical alteration can change an attractant to a reppelent
(e.g., Seudenol which is an attractant of douglas fir and spruce beetles
was transformed into 3-methyl-cyclohex-2-en-1-one which is a
reppelent of the same species).
 The use of reppelent pheromone on healthy trees can be combined
with the use of aggregation pheromone on dead or dying trees.
Mass trapping: Attract&Kill method
 Attractant: Ammonium bicarbonate;
 Pheromone: Virgin female sex pheromone;
 Insecticide: Pyrethroids (Deltamethrin in Eco-trap or
Lambda-Cyhalothrinin Agrisense).
Agrisense
Eco-trap
3
Definition of biological control
Biological control definition
Biological control can be defined as the use of natural
enemies to reduce the damage caused by a pest population.
Biological control is an approach that fits into an overall
pest management program, and represents an alternative to
continued reliance on pesticides.
Biological control definition
One definition of biological control that is easy to use and
to remember is that biological control is "three sets of
three". The sets of three represent:
 The "who": The natural enemies themselves that is to say
predators, parasitoids and pathogens.
 The "what": The objective to achieve which can be
prevention, reduction or delay of infestation.
 The "how": The approach that is taken with the natural
enemy to achieve the objective which can be conservation,
augmentation or importation.
Biocontrol history
Biocontrol history
 Predation, parasitism and insect pathology have different
histories;
 Predation has been more easily observed and recorded
than parasitism and disease because of larger size of insect
predators with respect to pathogens and parasitoids.
 Records from southern China indicate that weaver ant,
Oecophylla smaragdina, nests have been gathered, sold,
and placed in citrus orchards for approximately 2000 years.
 Date growers in Yemen placed colonies of predatory
ants in date palms for insect control.
 The beneficial aspects of coccinellid predation has been
recognized in Europe since the 13th century.
Biocontrol history
 Interpretation of insect parasitism and the development of insect
pathology were dependent upon the invention of microscopy.
 The earliest recorded observations in western Europe of insect
parasitism occurred during the 1600s.
 In 1602 Aldrovandi recorded observations of parasitic larvae of
Apanteles (Cotesia) glomeratus exiting from cabbage butterfly
(Pieris rapae) and spinning external cocoons.
 In 1670 Martin Lister correctly interpreted insect parasitism in a
letter published in the Philosophical Transactions of the Royal
Society of London.
Biocontrol history
 The importation of the vedalia ladybird beetle to California citrus
orchards beetle to reduce the population level of cottony cushion
scale can be considered as the beginning of the modern era of
biological control.
 This importation project saved the developing citrus industry in
California in the late 1800s and provided the impetus for biological
control efforts within California.
 This spectacular biological control success in California was
repeated in several other countries.
 Nowadays, many biological control agents are used with success
for the containment of many pests in almost all the countries.
Basic biological control theories:
populations dynamics, density-
dependance and alternative
theories.
Basic biological control theories
 There is a high diversity and complexity of theories and models in
biological control that try to understand the biology of natural
enemies and their impact on host (prey) population dynamics.
 The process by which densities of populations are maintained in
nature is referred to as "natural control".
 Natural control serves as the basis for biological control and other
pest control tactics.
 Understanding the major concepts of natural control is key to
understanding how natural enemies control pests and how they can be
used in biological control programmes.
 Biological control has contributed significantly to the theoretical
understanding of natural control..
Basic biological control theories:
population dynamics
 A population is a group of interbreeding individuals of the same
species located in a defined area.
 Early history of the field of ecology reflected the interest of
ecologists in determining a theoretical structure to explain the
observed patterns of population dynamics in order to identify the
relative role of factors responsible for causing population change.
 Understanding of natural control to which the majority of
biological control specialists subscribe is that populations exists at
a characteristic abundance, which is defined as the long-term
expected numbers of individuals in a population.
Basic biological control theories:
population dynamics
 Presence of a characteristic abundance suggested that
populations were being maintained around a given level (density)
through the actions of factors found in the local environment.
 Reduction and maintenance of introduced pest populations
following introduction of "exotic" natural enemies was seen as
confirming both the existence of a characteristic abundance and the
role natural enemies play in maintaining insect population
densities.
Basic biological control theories:
Density-dependance
 Maintaining population density around a characteristic
abundance required the action of factors that behaved in a density
dependent fashion.
 The tendency for population to be maintained around a
characteristic abundance via action of density dependent factor(s) is
referred to as population regulation.
 A factor that acts in a density-dependent fashion increases its
impact on the affected population as the density of the population
increases.
 Thus, natural enemies whose percentages attack rate increases in
response to host (prey) density increases are said to be acting in a
density-dependent fashion.
Basic biological control theories:
Density-dependance
 The need to have density-dependent factor(s) regulating
populations around a characteristic abundance was seen as necessary
to counter the potential exponential growth rate that all populations
possess.
 Without a factor(s) that acted in a density-dependent fashion,
populations would eventually grow to the point where they consume
their resource base and crash towards local extinction.
 The persistence of populations, and the relative lack of data for
local extinctions, was seen as confirming evidence for the existence
of density-dependence factors and the regulation of populations in
nature.
 Other than natural enemies, factors that act in a density-dependent
fashion are intra-and inter-specific competition and territoriality.
Basic biological control theories
Illustration of natural control: the
population number is fluctuating
over time it is bounded within a
range. The population's
"characteristic abundanc“, the long
term expected number of
individuals in the population, is
represented by the yellow.
Example of a factor that acts in
a density-dependent fashion
(http://www.inhs.uiuc.edu/cee/biocontrol/theoriesmodels/na
tcontrol.html)
Basic biological control theories:
Alternative theories
 Historically, the major challenge to the "density-dependent school"
came from those who felt that the evidence for population stability in
nature was not proved, and that the numbers of individuals in a
population was largely determined by the time available for population
growth.
 Population control can be accounted for via vagaries in
environmental limits that are not related to density per se.
 Whereas followers of the density-dependent school saw populations
existing in a characteristic abundance, those of the density-independent
school saw populations in flux, with extinctions common and the longterm expected number of a population only a statistical, not biological,
reality.
 The abundance and distribution of populations reflected adaptation
to local conditions that are limited as to the nature, magnitude and
direction of change.
Basic biological control theories:
Alternative theories
 Populations track environmental change, expanding in favourable
times and contracting during unfavourable periods.
 Population control was seen to have elements of maintenance
within boundaries ("control") and return to equilibrium
("regulation").
 Extinction of populations happens and the imposition of densitydependence occurs for only relatively short time periods.
 For the most part, it is a combination of so-called "imperfect
density-dependent" factors (including natural enemies) and densityindependent factors (primarily weather) that influence population
dynamics.
Basic biological control theories:
Alternative theories
 "Conditioning factors" uninfluenced by density, will control or set
the framework of environment upon which density dependent factors
act.
 At lower densities, either density-independent factors "relax" or
the population goes extinct. At higher densities, the only "perfect"
density-dependent factor, intra-specific competition prevents
continued population growth and causes the population to decline to
lower levels.
 Uunderstanding of the role of natural enemies in the natural
control of insect populations has evolved over time: Originally seen
as acting as so-called "perfect" density-dependent agents regulating
populations, more synthetic theories place the impact of natural
enemies within a context of overall environmental impact on
population dynamics.
Biological control objectives:
reduction, prevention or delay of
infestation
Infestation reduction
 Reduction of a pest population after it occurs at a damaging level
 It approximates the use of pesticides.
 A biological control agent is used after the pest population has
exceeded the economic threshold, with a goal of sufficiently reducing
pest density and maintaining a lower density over a long period of
time.
 The pest is not eradicated but simply reduced to non-pest status.
 This has been the historical approach for importing natural enemies
against exotic pests: Vedalia ladybird beetle against cottony cushion
scale.
Infestation prevention
 The objective is to keep the population of a potential pest from
reaching a high, or economic, level.
 Prevention requires early intervention, before a pest build-up
occurs.
 The action of a natural enemy early in the life cycle of the potential
pest can keep the population from reaching pest status.
Infestation delay
This objective is similar to prevention, in that both require early
intervention, before a population exceeds a threshold. However, delay
means that the population will eventually build up to a high level, but it
does so at a time when the species is no longer considered a pest.
Biocontrol approaches: The tactical
approach taken to achieve the objectives, which may
be conservation, augmentation or importation.
Conservation
 Conservation biological control basically means keeping alive and
enhancing the effectiveness of those natural enemies that are already
present.
 Many conservation approaches are easily integrated into production
regimens and can be very effective.
 Reduction of pesticides use is one of the most important tools in
conservation approach:
Use of fewer applications of pesticides,
Altering the timing or formulation of the pesticides,
Use of "soft" pesticides such as those based on natural products,
which may be less persistent and also less toxic to natural enemies.
 Integration of other control measures like agronomical ones.
Conservation
 Often, providing a missing requirement can make the difference
for a natural enemy:
Non-prey food sources, such as flowers that might produce
nectar or pollen.
Nesting sites for social insects (wasps) can lead to increased
population persistence and, as a result, greater predation against
certain pest species.
 Wood lots moderate temperature for some beneficial insects
especially parasitoids.
Habitat management or farmscaping
 Protection of natural enemies by incorporating beneficial practices
(alternative food sources, over-wintering sites, shelter, alternative
preys/hosts) and avoid harmful practices (insecticides, inappropriate
ploughing , irrigation and burning of crop residues).
 Hedges with native plant species that are easily attacked by
alternative preys and that produce nectar, pollen and fleshy fruits…
 Preserve dry walls, old and high trees, flowering borders, hedges
and perennial habitats and non-crop habitats
 Diversified cropping systems: double cropping, strip cropping,
cover cropping, and intercropping.
 Till the soil leaving some areas temporarily with weeds ;
 Keep fields covered in winter (cover-crops and natural weeding);
 Install artificial nests for insectivorous birds and bats.
Key considerations in drafting a farmscaping plan
 Ecology of pest and natural enemies and their movement behaviour,
 Timing ;
 Identification of strategies for increasing farm biodiversity;
 Insectary establishment.
Indicators for evaluating a farmscaping strategy
 Vegetation types and biodiversity;
 Prey/host abundance;
 Availability of complementary resources (nectar, pollen);
 Ratio of crop to interplanted land and spatial arrangement of
interplanted vegetation.
Principles for conserving and/or enhancing
agricultural biodiversity
Adoption of diversified farming systems:
 Diversification in time (crop rotation, sequences), space
(polycultures, agroforestry, mixed farming, intercropping..).
 Recycling and conservation of soil nutrients and organic
matter: use of plant and animal biomass and favours recycling
of nutrients and on-farm natural resources.
Integrated pest management and biological control.
Conservation and regeneration of natural resources: germoplasm
conservation; beneficial fauna and flora, soil health, water…
Enhance soil biodiversity: farming practices that minimise soil
disturbance, minimum or no-tillage, crop rotation, organic
amendments (manure, compost), recycling of plant residues…
Principles for conserving and/or enhancing
agricultural biodiversity
Application of agroecological principles;
Active participation and empowerment of native and
indigenous small farmers and the protection of their rights;
Adaptation of practices to local agroecological and
socio-economic conditions;
Conservation of local animal and plant genetic
resources;
Reforming genetic research and breeding programs
towards more respect of agrobiodiversity;
Creating a supportive policy environment.
Examples of hedge species planted in organic orchards
Mastic Tree,
Evergreen Pistache:
Pistacia lentiscus
Inula viscose
Gum arabic tree:
Acacia spinosa
Jujube berries:
Zizyphus sativa
Hegde species and beneficial
insects
 Family: Santalacee;
 Scientific name : Osyris alba L.;
 Common name: Poet's Cassia
(Ginestrella Comune in Italian).
Poet’s Cassica hosts many beneficial insects against olive moth
(Prays oleae) like Chelonus eleaphilus. Furthermor, they are also
some alternative preys of this beneficial insect living on Poet’s
Cassia.
Augmentation
 Augmentation biological control basically means adding natural
enemies, either where they are not present, or are present at small
numbers.
 Augmentation has been used more extensively in greenhouse
and interior settings than in crop settings, but there are examples of
successful use in nearly all settings.
 Two different approaches to augmentation: Inoculation of small
numbers of natural enemies, or inundating with large numbers.
Augmentation: Inoculation and
Inundation
 With inoculation, one begins with a small number and allows
the natural enemy populations to increase over time. In this case,
the pest population does not decrease quickly but can either be
prevented from reaching pest status or the population increase is
delayed.
 With inundation, one introduces a large number of natural
enemies, with the intention of reducing the population quickly.
Inundation has a greater associated cost, as the large number of
natural enemies either must be purchased or reared.
Importation
 Importation biological control means to introduce a new exotic
natural enemy from one environment to a new setting, hence
"importing" it.
 This approach is often called "classical" biological control.
 Some biological control practitioners consider this the only
"true" biological control approach.
Biological control agents:
parasitoids, predators and
pathogens.
Macro-organisms use in biocontrol
Predator, 52/
41%
Hyperparasite, 1/
1%
Parasitoid, 53
41%
Phytophagous, 21/
17%
(Copping, 2004)
Phytophagous biocontrol agents
Lepidoptera,
4/
19%
Mite, 1/
5%
Coleoptera,
14/
66%
Diptera, 2/
10%
(Copping, 2004)
Parasitoids
Parasitoids
 Parasitic insects (also known as parasites and parasitoids) are insects
whose immature stages (larvae) develop by feeding on or in the bodies
of their host arthropods, which are usually other insects.
 Host: The organism attacked and used as a food source by the
parasite. The recipient of the protagonist's action. Equivalent to a prey
used by a predator.
 Unlike true zoological parasites, parasitic insects kill their hosts.
 Parasitic insects are unique, because it is the immature stages that
kill the host.
 Nearly all parasite immatures develop on or in a single host.
Parasitoids
 Parasites are holometabolous, having complete development (egg,
larval, pupal and adult stages).
Adult parasites are free living; some species will feed on hosts
(predators), in addition to ovipositing in or on the hosts.
 In the world of parasites, only females are significant players, as
they are the ones that find and attack hosts. For some species, males
are not known to exist.
 The number of species of parasites is unknown and speculative,
ranging from an estimate of 800,000 to as many as 25% of all
insects.
Parasitoids types
Parasitoids are usually defined by:
 Where the egg is laid (inside the host = endoparasite;
outside the host = ectoparasite).
 The feeding habit of the immature stage (egg, larval,
pupal parasite, etc.).
 Whether one or more parasite progeny emerge from the
host (solitary vs. gregarious).
 Host-parasitoid interactions.
Parasitoids types
The feeding habit of the immature stage:
 Egg parasite: Parasite adult attacks the host egg, and the parasite
progeny emerge from the egg.
 Egg-larval parasite: Parasite adult attacks the host egg, but the
parasite progeny emerge from the larva.
 Larval parasite: Parasite adult attacks the host larva, and the
parasite progeny emerge from the larva.
 Larval-pupal parasite: Parasite adult attacks the host larva, but
the parasite progeny emerge from the pupa.
 Pupal parasite: Parasite adult attacks the host pupa, and the
parasite progeny emerge from the pupa.
Parasitoids types
Place of oviposition:
 Ectoparasite (External Parasite): Parasite develops externally on
the host with its mouthparts inserted into the host's body.
 Endoparasite (Internal Parasite): Parasite larva develops inside
the host's body.
Number of parasites’ progenies that emerge from the
host :
 Parasite species load: The number of parasite species that
usually attack a host species.
 Hosts range: The number of host species that are usually attacked
and utilized successfully by a parasite species.
Parasitoids types
Number of parasites’ progenies :
 Gregarious parasite: Multiple parasite eggs are deposited, the
larvae feed together on a single host, and multiple parasite offspring
emerge.
 Solitary parasite: Only one parasite egg is deposited per
oviposition event and generally only one progeny emerges from the
host.
 Polyembryonic parasite: Many (up to several thousand)
parasites emerge from a host, having arisen from asexual division of
one or two parasite eggs. Restricted to four families of parasitic
Hymenoptera (Braconidae, Dryinidae, Encyrtidae, Platygastridae).
Parasitoids types
Number of parasites’ progenies :
 Multiparasitism: A single host is attacked by more than one
species of parasites, and the second parasite species feeds on the
original host, not the other parasite species.
 Superparasitism: Several females of one species of parasite
attack the same host, or one female oviposits more than one egg,
with only one egg laid at a time. Often, only one progeny will
survive. This is not the same as gregarious parasitism, where a single
female lays many eggs in one oviposition bout.
Parasitoids types
Host-parasite interactions:
 Primary parasite: The parasite attacks and develops in or on a
host, and that host is not another parasite.
 Cleptoparasite: A parasite that requires a host to be parasitized
already.
 Facultative hyperparasite: Can develop either as a
hyperparasite in a host already parasitized by a primary parasite, or
it can develop as a primary parasite in an un-parasitized host.
 Heteronomous parasite (Autoparasite and Adelphoparasite):
Females develop as primary parasites of homopterans (whiteflies,
scales), but males develop as a hyperparasite of female primary
parasites of homopterans.
 Heterotrophic parasite: The female is a primary parasite of
homopterans, but the male is an obligate parasite of a completely
different host, such as eggs of Lepidoptera.
Parasitoids types
Host-parasite interactions:
 Idiobiont parasite: Parasite prevents continued growth by the host.
Hosts are often paralysed. Often egg, pupal, and adult parasites.
 Koinobiont parasite: Parasite allows continued growth and
development of the host. Host not paralysed. Egg-larval, larval-pupal
parasites, and larval parasites. The parasite larva either suspends
development as a first instar, or the parasite larva avoids feeding on
vital organs until late in development.
 Obligate hyperparasite: The hyperparasite can only develop as a
parasite of a primary parasite.
 Secondary parasite (Hyperparasite): The parasite attacks a host that
is another parasite.
Parasitoids taxonomy
 Although parasitism is found in several insects orders, primary
orders of parasites are Hymenoptera and Diptera.
 The greatest diversity of parasites is found in Hymenoptera.
 The most important parasitic families within Hymenoptera order
are: Dryinidae, Bethylidae, Chrysididae and wasps.
 Several Diptera families have members that are parasitic:
Acroceridae, Bombylidae, Cecidomyiidae, Cryptochetidae, Phoridae,
Pipincluidae, Tachinidae, and Sarcophagidae.
 Rare representative taxa are also found in the Coleoptera,
Lepidoptera and Neuroptera.
 Strepsiptera are true zoological parasites, as they do not kill their
hosts.
Hymenoptera parasitic families
Pteromalidae, 1/
Platyga-seridae, 2%
Trichogrammatidae, 6/
11%
Tachinidae, 1/
2%
Aphelinidae, 10/
18%
1/
2%
Mymaridae, 1/
9%
Aphidiidae, 4/
8%
Ichneumonidae, 1/
2%
Aphidiinae, 1/
2%
Eupelmidae, 1/
2%
Bethylidae, 1/
2%
Eulophidae, 1/ Encyrtidae, 1/
17%
8%
(Copping, 2004)
Dryinidae, 1/
2%
Braconidae, 7/
13%
Parasitoids-hosts interactions
 All parasites go through a series of processes by which they find,
attack and utilize their hosts.
 In order to understand better parasitoids-hosts interactions it is very
important to analyse the following main precesses: Habitat selection,
host location, host acceptance, host suitability, and host regulation.
 It is important to remember that there is a great overlap between
processes, and that some of the processes are less important for
particular parasites or in some settings.
 Each process is mediated by a multitude of cues (signals).
Parasitoids-hosts interactions:
Habitat selection
 Habitat selection is the first of the processes that affect host
utilization.
 The importance of habitat selection cues to biological control is that
they serve to get the parasite to the appropriate habitat in which they
may find the target pest, and thus have a greater chance of successfully
controlling the target pest.
 Parasites that respond to specific habitat cues also will show some
degree of habitat fidelity. The fidelity to particular habitat types means
that the parasites will not be likely to attack non-target species that may
be found in other habitats.
Parasitoids-hosts interactions:
Habitat selection
 Many parasites use cues from the habitat itself, independent of
whether hosts are present or not.
 The habitat selection cues are linked to the female's reproductive
state, as it has been seen that, before the female parasite's eggs are
mature, she is repelled by the same chemicals from the same plants
(habitats).
 Numerous examples exist of parasites being attracted to the
habitat of their hosts.
 These cues serve to get the parasite into an appropriate habitat, in
which hosts might be likely to be found.
Parasitoids-hosts interactions:
Habitat selection
 Cues serve to orient a parasite to a habitat, so most known habitat-
related cues are long distance.
 Cues used for habitat selection are usually visual, or volatile odours:
Visual cues: Drill-and-sting strategy in which the parasitoid drills its
ovipositor through the stem of a grass, ovipositing into an enclosed
lepidopteran pupa.
 Volatile odours or chemical cues: Chemicals existing in a certain
habitat give some indications about the presence of the parasitoid host
that emitted them.
Parasitoids-hosts interactions:
Host location
 In this process, the parasite is responding to cues that indicate the
presence of a host, but only after the parasite is in the appropriate
habitat.
 The cues serve to get the parasite from the "neighbourhood" of the
host (the habitat), to the specific location of the host.
 These cues tend to be more specific, intimate, and shorter distance
than habitat cues.
 Host-location cues can be chemical odours, visual (including
movement), sound (or vibration), or radiation.
Parasitoids-hosts interactions:
Host location
 The cues can be from the host itself, by-products from the host,
plants or other habitats used by the host, or even from other hostassociated organisms.
 Host’s cues: Sex/aggregation pheromones, sound, vibrations from
the enclosed hosts, movement, or the increase of habitat temperature
induced by host’s emitted radiation.
 Host by-products: By-products of host feeding or other behaviour
are often used as host-finding cues by a variety of parasites. Examples
include frass produced by corn earworm and stemborers, including
sugarcane borer, and honeydew produced via homopteran insects
feeding.
Parasitoids-hosts interactions:
Host location
 Host-plant cues: Examples include terpenes released by pines, but
only when being fed on by the host, specific damage induced by the
host (but not by artificial damage), hosts that reaches the stage in
which they are normally attacked by the host.
 Other associated organisms: Parasites respond to cues produced
not by the hosts, but by other organisms that are found in association
with the host. The utility of these cues depends on how intimate are
the other organisms with the parasite's host.
Parasitoids-hosts interactions:
Host acceptance
 Host acceptance is the yes-or-no decision made by the parasite
once it has found a host.
 The cues used include chemicals on the host surface or in the
hemolymph; and size, shape, age, or texture of the host. Often, it is a
series of cues, both physical and chemical, that lead to acceptance.
 Several egg parasites (Trichogrammatidae and Scelionidae) are
sensitive to size and shape of their egg hosts while Ichneumonids are
attracted to 3-dimensional cylindrical shapes, but only after
responding to chemical odours.
Parasitoids-hosts interactions:
Host acceptance
 Host-movement cues indicating acceptability of hosts are seen in a
variety of parasites.
 For several Trichogrammatids the movement of the developing
embryo within the egg signals the age (and unsuitability) of the host.
 Some Ichneumonids will not attack immobilized hosts, suggesting
that movement is required to tell hosts from non-hosts.
Parasitoids-hosts interactions:
Host suitability
 Once hosts are found and accepted, they still must be
physiologically and nutritionally suitable for the parasite progeny to
develop successfully.
 Hosts must provide the parasite progeny with a safe, nutritious
place to develop.
 Host size will affect parasite development, often larger hosts may
produce larger parasites, because of an abundance of food for the
progeny and to quicker progeny development.
 Hosts too small to provide parasites with sufficient nutritional
resources will lead to the death of parasite progeny.
Parasitoids-hosts interactions:
Host suitability
 Idiobiont parasites are limited to the resources the host provides
when attacked while koinobiont parasites are not limited by the size
or even the stage of the host attacked.
 Host age will also affect suitability. Eggs and pupae that have
already developed somewhat may be less suitable for development,
simply because of the difficulty for the parasite to metabolise their
tissues.
 Hosts, often, are protected by a variety of defences, such as the
immune system response of encapsulation of parasite progeny that
should be overcome by the parasitoid.
Parasitoids-hosts interactions:
Host regulation
 The host's immune response must be overcome to prevent the host
from killing the parasite eggs or larvae.
 This process overlaps with host location especially host defences
such as the immune response.
 The parasite must be able to regulate the host's development and
immune systems.
 The parasite must control moulting of larval host, so that it doesn't
pupate before the parasite completes development.
Predators
Predators
 Predation can be defined as a trophic level interaction in which one
species derives energy from the consumption of individuals of another
species.
 A predator is considered an entomophagous species that generally
consumes more than one prey individual to complete its development.
 Some parasitoids host-feed as adults which could be considered a
type of predation.
 Over 16 orders of insects contain predaceous members, in
approximately 200 families. Including spiders and mites, there are
probably in excess of 200,000 species of arthropod predators.
 Many crops contain a rich assemblage of predators, and it is not
uncommon to find 300-500 species of predators in a given crop.
Predators
 Among the non-insect arthropods, spiders (Araneae) represent the
largest, most diverse group. Spiders have been little utilized in
biological control.
 Mites (Acari) have a number of predaceous members, most found
in the family Phytoseiidae. Mites have been used in a number of
biological control projects.
 Monophagy: A highly specialized prey range, the predator may
feed on one or a very limited number of species within the same
genera.
 Oligophagy: A semi-restricted prey range of a predator. For
example, aphidophagous predators feed primarily on aphids preys, or,
genera of coccinellids feed primarily on whiteflies or scales.
 Polyphagy: A broad prey range, may include plant materials
(fluids, nectars, pollen), insects and fungi, a generalist predator.
Predators’ characteristics
Generally speaking the most common features of insect predators are:
 kill and consume more than one prey organism to reach maturity;
 Relatively large size compared to prey;
 Predaceous as both larvae and adults;
 Larvae are active with sensory and locomotory organs;
 Except for predatory wasps that store prey for immature stages, prey
are generally consumed immediately.
Frequency of individual prey items in the diet may be influenced by:
 Prey environment;
 Prey preferences;
 Competition with other predators;
 Suitability of prey.
Preys location and capture
Strategies used by predators to locate and capture preys include the
following:
 Random searching: The predatory bug, Podisus maculiventris,
searches bean plants without using cues, but did not search areas
repeatedly once a prey was found.
 Directed searching: Supposing a certain capacity of orientation to
objects in the microhabitat. Movement may be guided by features of
the environment that increase chances for encountering prey.
 Active searching: Use of visual cues and other stimuli to orient to
prey at a distance.
 Ambushing: Waiting for prey to approach within a striking distance
then with their raptorial legs (praying mantids) they clasp their preys.
 Trapping: Neuropterans prepare conical pits in loose sand, larvae
wait at the bottom with large sickle shaped jaws.
 Attracting: Lightning bugs, flashing of one species to attract males
of another. Females then consume males.
Predators groups
Mesostigmata,5/
10%
Neuroptera,
2/
4%
Orthoptera, 1/
2%
Thysanoptera, 2/
4%
Acari, 10/
19%
,
Hemiptera, 9/
17%
Gastropoda,
1/
2%
Diptera, 3/
6%
(Copping, 2004)
Coleoptera,
17/
32%
Predatory insect groups
The major groups of predaceous insects belong to the following
orders: Coleoptera, Dermaptera, Diptera, Hemiptera, Hymenoptera,
Mantodea, Neuroptera, Orthoptera and Thysanoptera.
 Coleoptera:
 Coleoptera (beetles and weevils) is the largest order in the class
Insecta.
 Many Coleoptera species are herbivores, others live on fungi but
many beetles are predators. There are even few parasitic beetles.
 The most important Coleoptera predaceous families are the
following: Carabidae (ground beetles); Cicindelidae (tiger beetles),
Staphylinidae (rove beetles); Lampyridae (fireflies); Cantharidae
(soldier beetles) and Coccinellidae (ladybird beetles).
Predatory insect groups
 Dermaptera:
Members of the order Dermaptera are recognized by pincers at the
tip of the abdomen. These structures are used to hold prey while it is
being consumed.
 The predaceous species feed on soft bodied insects (e.g. aphids, leaf
hoppers, larvae of Coleoptera and Lepidoptera).
 The most important Dermaptera predatory families are: Forficulidae
(spine tailed earwigs); Labiduridae (striped earwigs) and Labiidae
(little earwigs).
Predatory insect groups
 Diptera:
 Some flies are predators of other arthropods (e.g., robber flies), but
most of them are external parasites (e.g., mosquitoes and deer flies).
 Families that contain predaceous species are: Asilidae (robber flies),
Empidae, Dolichopodidae (longlegged flies), Rhagionidae, Tabanidae,
Tipulidae, Chamaemyiidae, Cecidomyiidae (midges), and Syrphidae
(hover flies). Species in the later three families have been used in
biological control.
Hemiptera:
 Hemiptera is a large, cosmopolitan order of insects, comprising
some 67,500 known species in three suborders: Auchenorrhyncha,
Sternorrhyncha and Prosorrhyncha.
Predatory insect groups
 Hemiptera:
The most relevant Hemiptera predatory families are: Miridae (plant
bugs); Nabidae (damsel bugs), Anthocoridae (insidious flower bugs),
Reduviidae (assassin bugs), Phymatidae (ambush bugs), Lygaeidae
and Pentatomidae (stink bugs).
 Hymenoptera
 Hymenoptera is one of the larger orders of insects, comprising
sawflies, wasps, bees, and ants.
 Females of Hymenoptera typically have a special ovipositor for
inserting eggs into hosts or otherwise inaccessible places, often
modified into a stinger.
 The most important Hymenoptera predaceous groups are:
Sphecidae (sphecid wasps); Vespidae (paper wasps, yellow jackets);
Eumenidae (mason and potter wasps) and Formicidae (ants).
Predatory insect groups
 Neuroptera:
The insect order Neuroptera includes the lacewings, mantidflies,
antlions, and their relatives. The order contains some 4000 species.
 The adults of this order possess chewing mouthparts, and most are
predatory.
 The most important Neuroptera predaceous species belong to the
following families: Chrysopidae (green or common lacewings),
Hemerodiidae (brown lacewings), Mantispidae (mantid-flies),
Coniopterygidae (dusty wings) and Myrmeliontidae (antlions).
 Orthoptera:
The Orthoptera order includes the grasshoppers, crickets and locusts.
 The most important Orthoptera predaceous species are included in
Gryllidae (tree crickets) which are Omnivorous on soft bodied insects,
aphids and scales.
Predatory insect groups
Thysanoptera:
Most species of Thrips feed on plant tissues (often in flower heads),
but some have been reported to feed on phytophagous mites, thrips,
whiteflies, and lepidopteran eggs.
The most important Thysanoptera predatory
Phlaeothripidae and Aelothripidae (Banded thrips).
families
are:
 Mantodea:
 Mantids have elongate bodies that are specialized for a predatory
lifestyle: long front legs with spines for catching and holding prey, a
head that can turn from side to side, and cryptic coloration for hiding
in foliage or flowers.
The most important predaceous family is Mantidae (praying
mantid).
Predator-prey interactions
The sequence of behaviours used by predators to locate prey is similar
to that for parasitoids. In general, behaviours are not as clearly defined
for predators as for insect parasitoids.
 Prey habitat location:
 For predators associated with ephemeral habitats (e.g. agricultural
crops), adults must locate habitats with prey through seasonal
movements into and out of cropping systems.
 Olfactory and visual cues are likely used by adult predators to
locate suitable habitats.
Volatile kairomones and synomones are known to be used as
attractants by selected insect predators.
 For some predatory species, a blend of compounds, including
volatiles from the plants in the habitat as well as prey volatiles, are
involved. This blend is called synergistic mixture of plant and prey
derived cues.
Predator-prey interactions
 Prey location:
 Physical and chemical cues are used by many predatory species to
locate prey. Vision may be important for ambush type predators or
other predators of slow-moving prey. Kairomones can be used for
short range perception of prey.
 Larval predators have evolved various means of locating and
recognizing their prey through phototactic and/or geotactic responses,
vision, olfaction, sound or vibration detection, or physical contact.
 Some larval predators switch from linear movement to areaintensive searching after they contact prey.
 A predator's previous experience (learning) can influence its
searching behaviour, as well as the type and proportion of prey taken
within an area.
Predator-prey interactions
 Prey acceptance:
 Once a prey item is contacted, the behaviour used to initiate and
continue feeding on prey.
 Generalist predators attack, subdue and consume a wide range of
prey species they encounter.
 The following may influence prey acceptance: size of prey, antipredator behaviours of prey, and composition of cuticle.
 Morphological and physiological factors can influence prey
acceptance.
 Size, shape, movement, and external and internal chemical cues of
prey are factors that can be used as stimuli to induce prey acceptance.
 Many insect predators are stimulated to bite or taste a prey
following antennal or palpal contact.
Predator-prey interactions
 Prey acceptance:
 One underlying physical factor that influences prey acceptance is
the size of prey relative to the predator.
Prey integumentary chemicals (e.g., waxes) may serve as
kairomones or phagostimulants for some predatory species.
 Another aspect of prey acceptance involves prey behaviours and
defences. Some prey (e.g. aphids) kick, run, drop, or fly away, or
exude noxious chemicals when predators approach them.
 Prey preference: The consumption of a prey species in greater
proportion than its relative abundance among possible prey items.
 Prey specificity: Properties of a predator which limit types of prey
attacked, may involve behavioural, spatial, and temporal aspects.
Predator-prey interactions
 Prey suitability
 Prey suitability can be considered as the influence of the nutritional
composition of the prey on the development, survival, and
reproduction of a predator.
 If prey are not suitable (i.e., they have low nutritional quality), the
predator may reject the prey, or it may continue feeding, but with
detrimental effects.
 The negative effects may include reduced rates of development,
reproduction (fecundity) or survival.
 Prey suitability may or may not be the same for immature and adult
stages of a predatory species.
 Lack of information on prey suitability explains why relatively few
insect predators can be mass-reared successfully, and even fewer can
be reared on artificial diets.
Pathogens
Pathogens
 Associations between Microorganisms and insects range from
mutualistic associations to those where the microorganism causes
fatal disease in the insect host.
 Infectious insect diseases, usually causing deleterious effects in
the invaded host, occur frequently in insects and often act as
important natural control agents.
 Insect pathogens are most often viewed as microbial insecticides.
 It is very important to distinguish between diseases of insects
caused by pathogens, those that are caused by non-infectious agents
and also to distinguish between pathogenic and non-pathogenic
micro-organisms that live in symbiosis with insects.
Pathogens
 Entomogenous: Organisms growing in or on the bodies of insects;
usually connotes a parasitic or other intimate symbiotic relationship.
 Entomophagous: Insectivorous; the consumption of insects and
their parts.
Entomophilic: Associations between insects and other organisms,
e.g. plant, microorganisms, Protozoa, and nematodes.
 Horizontal transmission: Transmission of a pathogen from
infected individuals to conspecific individuals within a generation or
overlapping generations in a season.
 Vertical transmission: Transmission of a pathogen from one
generation of host to the next.
 Transovarial (or transovarian) transmission: Transmission
from one generation to the next via the egg. The pathogen is
transmitted within the ovary of the infected female and usually is
found in the cells of the embryo.
Pathogens
Transovum transmission: Transmission from one generation to
the next via the egg. The pathogen can be on the surface of the egg
and ingested upon hatch of the neonate host, or can be within the host
embryo (transovarial transmission). Transovarial transmission is a
special case of transovum transmission.
Invasion/Infection: Invasion is the entry of a microorganism into
the host body. Primary invasiveness is a property of pathogenic
microorganisms. Infection implies that the pathogen enters the body
of the host, usually the cells, and be able to reproduce to form new
infective units. Simply ingesting a pathogen does not imply infection.
 Latent infection: Unapparent infection; the pathogen is in a nonreproductive phase and a pathogen-host equilibrium is established.
Pathogenicity and virulence: Pathogenicity is the ability of an
organism to invade the host and cause disease.
Non-pathogenic organisms & insects
associations
 Technically, the living together of dissimilar organisms regardless
of the result of such an association is called symbiosis.
 Every insect/microorganism association is a symbiotic association
and this would include all associations discussed within the subject
area of biological control.
 When examining insects and diagnosing insect diseases, nonpathogenic organisms are often encountered and may be confused
with true insect pathogens.
 There are mainly two kinds of insect/non-pathogenic organisms
associations: Casual and mutualistic associations.
Non-pathogenic associations
 Casual associations:
 Insects harbour microorganisms that occur in their immediate
environment. Bacteria, fungal conidia, free living Protozoa and other
organisms adhere to the cuticle of insects and may pass through the
digestive tract.
 Such associations are largely accidental and are usually neither
harmful nor beneficial to either insect or microorganism.
 Mutualistic associations:
 Most groups of organisms (viruses, bacteria, fungi, and Protozoa)
have mutualistic associations with insects. These associations may be
either intracellular or extracellular and are usually associated with insects
that have some nutritional difficulty.
 The microorganisms provide a required nutritional compound or an
enzyme necessary for converting an unusable into a usable food product.
 Although there have been attempts to manipulate mutualistic
associations as a means of biocontrol, the potential of this approach
appears limited at this time.
Non-infectious diseases of insects
 Generally speaking we can distinguish between non-infectious
diseases caused by abiotic agents and infectious diseases caused by
pathogens.
 It is of paramount importance to be able to distinguish between
these two kinds of infections that can cause insects death in order to
assess accurately and precisely the efficiency of biological control
means.
 Physical injuries, chemical injuries, nutritional deficiencies,
genetic abnormalities, and neoplasms may result in a disease state.
 With the exception of sterility, non-infectious diseases are seldom
considered a component of a biological control program.
 When evaluating individual insects or a population of insects for
the underlying causes of disease, researchers should be aware of
several possibilities other than infectious diseases.
Non-infectious diseases of insects
 Physical injuries:
 Insects are naturally somewhat protected from injury by the
cuticle, tracheal system, and physiological adaptations.
 Injuries occur and include distension (blockage), trauma such as
abrasions/contusions/ concussions/crushing, and open wounds.
 These injuries may include blood loss, tissue changes, and
exposure to pathogens.
 Extreme cold and heat, as well as solar radiation and drought, can
harm insects, often figuring strongly in the increase or decline of
insect populations.
 Chemical injuries:
 Chemically poisoned insects can have the appearance of pathogeninfected insects.
Non-infectious diseases of insects
 Chemical injuries:
 Plant secondary compounds can poison non-adapted hosts, as can
toxins produced by microorganisms.
 Toxins are sometimes
entomopathogens.
a
factor
in
the
virulence
of
 Insecticides may be physical poisons, protoplasmic poisons,
metabolic inhibitors, hormone mimics, stomach poisons, or
neuroactive agents.
 Most synthetic insecticides are neurotoxins.
 Genetic diseases:
 All hereditarily transmitted biochemical, physiological, and
morphological characters which are harmful for the organism are
genetic diseases.
Non-infectious diseases of insects
 Genetic diseases:
Genetic diseases may be classified as:
 Lethal factors: mutants or deficiencies.
 Sterility factors, usually chemical or irradiation mutations of males,
have been used successfully in biological control programs.
 Structural alterations include any malformations such as winglessness,
deformed body parts, supernumerary appendages, etc.
 Tumors.
 Gynandromorphs are inter-sex mutants that are usually sterile.
 Neoplasms:
 They are abnormal masses of tissue, the growth of which exceeds and
is uncoordinated with that of normal tissue and persists in the same
excessive manner after cessation of the stimulus that evoked the change.
 Etiologies may include carcinogens, inflammation, trauma, and
viruses.
Non-infectious diseases of insects
 Biological agents:
 Predators that don't kill insect prey outright may leave wounds for
which the same responses occur as for other physical injuries.
 Parasites may cause irritation and destruction of tissues, resulting
in mechanical injury, for example, piercing of the host integument by
female parasitoids, and surface feeding or feeding on (usually nonvital) tissues.
 Emergence of endoparasites usually causes death of the host.
 Parasitoids may also cause paralyzation and other physiological
injury due to competition for nutrients, or parasite castration.
 Nutritional diseases:
 Deviations from basic conditions needed for attraction to and
survival on a food source can lead to nutritional disease.
Non-infectious diseases of insects
 Nutritional diseases:
 Improper balance of nutrients, amino acids, proteins, fats,
carbohydrates, vitamins, inorganic ions, etc. can cause various
symptoms of nutritional disease.
 Limited feeding reduces growth, development, and reproduction.
 When insect populations outbreak, over-utilization of the food
source can result in starvation of not only the outbreak species but
also of other species utilizing the same food sources.
 Symptoms in larvae include severely affected growth rates and
development.
 Often adults have deformed wings, and mating and egg production
may be seriously affected.
Infectious diseases of insects
 Infectious agents are living units that must invade the insect host in
order to initiate an infection. Unlike parasites and predators, pathogens
do not always kill the hosts. Infection usually involves reproduction of
the agent.
 Invasion of the host may be dermal, body opening, oral by
feeding/drinking, or introduced by stings of contaminated or infected
parasites.
 The specific characteristics of the infective stages of pathogens greatly
influence how they contact and infect their hosts.
 The infectious agents responsible for transmission of the pathogen are
susceptible to many environmental factors: Few can survive more than a
few hours of direct sunlight. Others may be particularly susceptible to
dry conditions, high temperatures, freezing, and many chemicals.
 Survival of the infective stage of insect pathogens outside the host is a
major factor in the development of microbial insecticides.
Infectious diseases of insects
All insect pathogens have a physiological host range in which they can
potentially survive and reproduce.
 Some pathogen species may be very host specific, while others may
be able to infect a wide range of insect species.
 The host range of a pathogen is especially important when considering
a non-indigenous pathogen for introduction into a new habitat.
 Sub-lethal infections are not uncommon and these may include
behavioural and developmental changes as well as a decrease in the
fecundity of infected adults.
 Insects are infected by an incredibly large number and diversity of
pathogen species. Most insect pathologists believe that there are actually
more species of insect pathogens than there are species of insects.
 The major pathogen groups containing species that infect insects are:
viruses, bacteria, fungi, protozoans, microsporidia, and nematodes.
Use of pathogens in insect biocontrol
Insect pathogens are used in biological control in at least three different
ways: inundative applications, inoculative releases, management of
naturally occurring pathogens, and introduction of exotic pathogens as
classical biological control agents.
 Inundative applications:
They are those in which insect pathogens are applied in large
quantities with the goal of killing as many individuals of the pest
population as quickly as possible.
 Pathogens used in this manner are called microbial insecticides.
 Replication of the pathogen in the host and production of additional
infectious propagules may be desirable, but is not usually required for
microbial insecticides to be effective.
Use of pathogens in insect biocontrol
 Inoculative applications:
 Inoculative applications are those in which small quantities of
insect pathogens are applied or released into an insect host
population.
 The goal is to produce infections in at least a few hosts, which
will, in turn, produce numerous infectious propagules that will infect
many more susceptible hosts.
 Introduction of exotic pathogens as biocontrol agents:
 Hundreds of exotic parasitoids and predators have been introduced
into different countries as classical biological control agents however
few exotic species of pathogens have been intentionally introduced.
 Difficulties in identifying and isolating insect pathogens, along
with regulatory uncertainties, have contributed to the underutilization of insect pathogens as exotic biological control agents.
Use of pathogens in insect biocontrol
 Management of naturally occurring pathogens:
 Insect pathogens are important components of the natural enemy
complex of many insect species, including pest species.
 Some groups of pathogens, such as microsporidia, may not always
maintain host insect densities below economic thresholds, but they
suppress the rapid increase of pest populations.
 Insects pathogens and are often responsible for the decline of
populations that have exceeded the economic threshold.
 In most cases the major goal for managing naturally occurring
insect pathogens is to elicit an epizootic earlier in the season, before
the host densities have exceeded the economic threshold.
 This can be accomplished by inoculative releases of the pathogen
or by changing cultural and phyotosanitary practices to promote an
epizootic.
Micro-organisms use in biocontrol
Microsporidia, 2
Nematodes,
9
Bacteria, 36
Baculoviruses, 16
Fungi, 49
(Copping, 2004)
Micro-organisms use in biocontrol
Fungicide, 35
Insecticide, 50
Herbicide, 12
Acaricide, 1
Fungicide, 35
Fungicide and nematicide, 1
Herbicide, 12
Insecticide and acaricide, 1
Nematicide, 5
Bactericide, 2
Fungicide and bactericide, 2
Fungicide and plant growth regulator, 1
Insecticide, 50
Molluscicide
Plant growth promoter, 1
(Copping, 2004)
 Insect viruses:
Types pathogens
Viral diseases have been found in 13 insect orders and most likely
occur in all orders. Viruses that are primarily or exclusively found in
insects are currently placed in 12 families (Miller, 1998):
 DNA Viruses: Baculoviruses (Nuclear polyhedrosis viruses- NPV
and Granuloviruses-GV), Ascoviruses, Iridoviruses, Parvoviruses,
Polydnaviruses and Poxviruses.
 RNA Viruses: Reoviruses (Cytoplasmic polyhedrosis viruses),
Nodaviruses, Picorna-like viruses and Tetraviruses.
 Bacterial pathogens:
They can be divided into two broad categories, non-spore-forming
bacteria and spore-forming bacteria.
Although most of the species isolated from diseased insects are
non-spore-forming, spore-forming bacteria in the genus Bacillus are
the most important from the standpoint of biological control.
Types pathogens
 Fungal pathogens:
 Entomopathogenic fungi are able to invade their insect hosts by
penetrating directly through the cuticle.
The fungal spore first adheres to the cuticle.
 Under appropriate conditions the spore germinates, penetrates the
cuticle of the host and enters the hemocoel.
 Fungal reproduction occurs in the hemocoel of the insect host.
 As the hemocoel becomes filled with hyphal bodies, the insect
usually dies and the fungus continues to develop saprophytically.
 After the body of the dead insect is filled with mycelia, fruiting
structures emerge from the cadaver and produce infectious spores.
 Dead insect has the consistency of a moist loaf of bread and,
depending on the colour of the spores or conidia, may appear white
or some darker colour.
Types pathogens
 Fungal pathogens:
 Tanada and Kaya (1993) listed 8 classes, 13 orders and 57 genera
that contain entomopathogenic species of fungi.
 There are five major groups of fungi: the Flagellate fungi or
Chytridiomycetes, the Oomycetes (also flagellate but also not true
fungi), the Zygomycetes, the Ascomycetes, and the Basidiomycota.
 The Zygomycota and the Ascomycota contain common insect
pathogens that are also useful in biological control programs.
 Microsporidia:
 Microsporidia are important primary pathogens of insects.
 Their best use will probably be as augmentatively released or
classical biological control agents, not as pesticides.
Types pathogens
 Microsporidia:
 The only microsporidian ever registered as a microbial pesticide
(in the USA) is Nosema locustae, a pathogen of grasshoppers.
 Two other microsporidian species that are known to control
populations of pest insects: Nosema fumiferanae and Nosema
pyrausta.
 Protozoa:
 Protozoa are the most taxonomically diverse group of insect
pathogens.
 Protozoa range in their interactions with insects from
commensualists and mutualists, to plant and animal pathogens
vectored by insects, to acute insect pathogens.
Types pathogens
 Protozoa:
 Of some 14,000 described species of Protozoa, about 500 are
pathogens of insects. Many are chronic pathogens that may debilitate
a host without producing obvious disease symptoms but some species
are extremely virulent, causing stunted growth, slow development,
and early death.
 Entry into the host is typically by ingestion, but some can invade
through the cuticle.
 Some species may be transovarially transmitted from infected
females to their offspring.
 Species that invade the cells of the host are usually found in the
cell cytoplasm and are typically more pathogenic than extracellular
species.
 Some protozoans exhibit tissue tropism, infecting only certain
tissues or organs, others are systemic.
Types pathogens
 Protozoa:
 No toxins have been found to be associated with protozoa in insects.
 Death or debilitation of infected hosts may be, for example, the
result of competition for metabolites, disruption of normal cell and
tissue function, or blockage of the gut or other organs by extracellular
species.
 The insect-pathogenic Protozoa are currently recorded from four
major groups: Amoebas, Gregarines, Flagellates and Ciliates.
 Nematodes:
 Some entomogenous nematodes have characteristics that allow them
to be considered with the pathogens.
 The most important insect pathogenic nematodes for biological
control are very small and use mutualistic bacteria to kill the host.
 Nematodes:
Types pathogens
 Although nematode species in at least 20 families are primary or
facultative parasites of insects, those in the order Rhabditida have
been most exploited as biological control agents.
 Species in the genera Steinernema and Heterorhabditis
(Steinernematidae and Heterorhabditae, respectively), are particularly
amenable to mass production and application in a variety of pest
systems.
 Entomopathogenic nematodes enter the host via natural body
openings or through the cuticle.
 Some species utilize an anterior stylet or a tooth to rasp the cuticle
and gain entrance into the hemocoel.
 Others ingress by ovipositing on the host food source and the eggs
hatch in the host midgut.
 Effects of nematode parasitism on the hosts can be sterility,
reduced fecundity, reduced mobility and life span, behavioural and
morphological changes, and death.
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