NEW DEVELOPMENTS IN THE MASS
PRODUCTION OF PREDATORY BUGS
Patrick DE CLERCQ, Eric RIDDICK & Tom
COUDRON
Dept. Crop Protection, Ghent University, Ghent, Belgium
National Biological Control Laboratory, USDA-ARS, Stoneville,
MS, USA
Biological Control of Insects Research Laboratory, USDAARS, Columbia, MO, USA
PREDATORY BUGS IN AUGMENTATIVE
BIOLOGICAL CONTROL
• Several species of predatory bugs (Heteroptera) are
economically important biological control agents
• Most are polyphagous, feeding on a wide array of
arthropod prey; many species can also exploit plant
resources (omnivory)
• Important heteropteran predators used in augmentative
biological control include:
– Anthocoridae: Orius spp. (thrips, aphids…)
– Miridae: Macrolophus pygmaeus, Nesidiocoris tenuis
(whiteflies, leaf miners, spider mites…)
– Geocoridae: Geocoris spp. (whiteflies, thrips, mites…)
– Pentatomidae: Podisus, Perillus, Arma spp. (lepidopteran
and coleopteran larvae…)
– Reduviidae: Rhynocoris, Zelus spp. (lepidopteran larvae…)
PREDATORY BUGS IN AUGMENTATIVE
BIOLOGICAL CONTROL
Nesidiocoris tenuis
Arma chinensis
Orius laevigatus
Macrolophus sp.
Geocoris sp.
Zelus sp.
REARING OF PREDATORY BUGS FOR
BIOLOGICAL CONTROL
• The main challenge for augmentative biological
control is a wide availability of cheap and effective
natural enemies for the growers
cost-effective
and reliable mass production of high-quality natural
enemies is essential
• The present paper will review developments in the
rearing of predatory bugs as related to:
– Foods: natural, factitious, artificial
– Plant materials and alternatives
– Rearing techniques and colony maintenance???
– Quality assurance
REARING SYSTEMS FOR PREDATORY BUGS
BASED ON FOOD TYPES
• Natural rearing systems: use the natural or target
prey for production of the predator, usually on a host
plant
• Systems using factitious prey: organism that is
unlikely to be attacked by a natural enemy in its
natural habitat, but that supports its development
and/or reproduction; usually a species that is easier
and less expensive to rear; with or without plant
materials
• Artificial rearings systems: use inanimate artificial
foods and preferably no plant materials
NATURAL REARING SYSTEMS
• In natural rearing systems the beneficial is reared on its
target prey or host, which itself is maintained on its host
plant (or on plant parts)
"tritrophic" system
• These systems can be economically viable: Encarsia
formosa, Phytoseiulus persimilis
• Possible drawbacks are:
• tritrophic rearing systems are expensive due to space and
labour needed for plant production
• there may be discontinuity problems at one or more of the
trophic levels to be maintained (e.g. diseases or other pests
attacking host plants)
• plant materials should be free of pesticide residues!
• there are risks of contamination associated with the release
of beneficials reared on natural substrates
FACTITIOUS, UNNATURAL OR ALTERNATIVE
FOODS
• The use of factitious foods may allow some rationalization
or automation of production or release
• Factitious host or prey: organism that is unlikely to be
attacked by a natural enemy in its natural habitat, but that
supports its development and/or reproduction
• Usually a species that is easier and less expensive to rear
• Examples:
– Storage mites for predatory mites (Phytoseiidae, Laelapidae)
– Eggs of lepidopterans for insect predators
– Brine shrimp cysts for predatory insects and mites
Eggs of lepidopterans
• Eggs of several easily reared lepidopteran species can be
used as a factitious food for arthropod predators and
Trichogramma egg parasitoids: Ephestia kuehniella,
Sitotroga cerealella, Corcyra cephalonica…
• Eggs are frozen or (UV, gamma) irradiated for use
• Eggs of E. kuehniella are a nutritionally adequate food for >
10 spp. of predators and several Trichogramma spp.
72% water; dry matter: 46% protein, 34% fat (>50% is 18:1), 8.5%
carbohydrates
• High price of E. kuehniella eggs (ca. 500 EUR/kg) due to
investments for climatization and mechanization, and foods
• Production poses possible health hazards for workers
(allergy to scales)
Eggs of the Mediterranean flour moth Ephestia kuehniella are
the basis for rearing Orius, Macrolophus, Adalia,
Chrysoperla… and Trichogramma egg parasitoids
Looking beyond the borders: the Artemia story
• Cysts (= diapausing eggs) of brine shrimps, Artemia sp.
(Crustacea), are a feed used in aquaculture for shellfish
and fish production
• The cysts were developed as a factitious food for
predatory insects at Ghent University
• The cysts can be offered to the predators in encapsulated
or decapsulated form (= rigid outer shell removed with
hypochlorite), and in hydrated or dry form
Non-decapsulated
Decapsulated
Artemia cysts versus
Ephestia eggs
Looking beyond the borders: the Artemia story
• Artemia cysts proved acceptable for predators with both
chewing and piercing-sucking mouthparts
• Artemia cysts have now replaced Ephestia eggs in the
commercial production process of predatory bugs; they
also hold promise for the rearing of predatory mites
• Cysts can be offered in part of the life cycle (e.g. nymphal
stage) or in a mixture with Ephestia eggs
• Cost of cysts is 1/10th or less of that of Ephestia eggs;
cysts can be easily stored in dry form
ARTIFICIAL DIETS
• The availability of an artificial diet may offer further
possibilities to automate the rearing process
• Types of diets:
 Diets with and without insect components (e.g.,
whole insect bodies, hemolymph...)
 Oligidic, meridic and holidic diets:
- Holidic: chemically defined diets (amino acids, fatty acids,
sugars, vitamins, minerals...)
- Meridic: holidic base with one or more unrefined or
chemically unknown substances (e.g., yeast, liver
extract...)
- Oligidic: containing only crude organic materials (e.g.,
meat diets)
HOLISTIC METHOD FOR DEVELOPING AN
ARTIFICIAL DIET
ARTIFICIAL DIET
Mix of proteins
Biochemical analyses
of preferred food
(amino acids, fatty acids,
sugars, …)
Digestive enzymes
of the predator
Biochemical composition
of the artificial diet
Copy
Computing
Mix of fats and oils
Copy
(amino acids, fatty acids,
sugars,…)
Growth factors
(vitamins, minerals,
proteins…)
Water content
Biochemical analyses of
natural enemy
fed on artificial diet
Physical properties
(gelling or filling agents,
encapsulation…)
Preservation
The right components, in the right proportions and taking
account of possible interactions among the components
Orius laevigatus feeding on a meat and liver diet
wrapped by hand in Parafilm
Egg yolk based artificial diet for Macrolophus pygmaeus
in machine-made Parafilm domes
PLANTLESS REARING SYSTEMS
• Many arthropod natural enemies
require plants for successful
development and reproduction:
– Source of water and supplementary
nutrients (omnivory!)
– Living substrate and refuge
– Oviposition substrate (e.g. Macrolophus,
Orius)
• If plant materials could be omitted
from the rearing systems, there
would no longer be a need to
maintain large surfaces of
greenhouses or to purchase (often
pesticide contaminated) plant
materials on the market
PLANTLESS REARING SYSTEMS
• Omission of plant materials from the rearing system of
beneficials would require the development of artificial
moisture sources, living and oviposition substrates
• Such substrates are now being used for mass production of
certain predatory bugs
Nesidiocoris tenuis
Hydrocapsules filled with water as an artificial moisture
source
Nesidiocoris tenuis
QUALITY OF NATURAL ENEMIES REARED
UNDER UNNATURAL CONDITIONS
• When rearing a natural enemy on a factitious host or
artificial diet, loss of fitness may occur because of genetic
or non-genetic changes in biological, biochemical,
physiological and behavioural traits, which may affect its
quality as a biocontrol agent => need for quality
assurance!
• Nutritional deficiencies may only become clear after
several generations, leading to lower viability and/or
reproduction (e.g. Orius bugs on Artemia cysts) markers
• Genetic adaptation and associative learning may affect
host/prey acceptance or parasitization/predation capacity
of a parasitoid/predator reared on an unnatural food (e.g.
lower acceptance of target host Ostrinia nubilalis in
Trichogramma parasitoids after long term rearing on E.
kuehniella eggs)
Age specific fecundity of Orius laevigatus in the first and
third generation on Artemia cysts
12
Number of eggs per female per day
Eph G1
Eph G3
10
SFB G1
8
SFB G3
6
4
2
0
0
10
20
30
Time (days)
40
50
60
QUALITY OF NATURAL ENEMIES REARED
UNDER UNNATURAL CONDITIONS
• Assessing developmental and reproductive fitness of natural
enemies is often tedious and time consuming
• Rapid tools to assess reproductive potential include:
– Correlating easily measured parameters (e.g. size) with
fecundity
– Dissection tests to count oocytes in ovaria
– ELISA-based detection of yolk proteins
dorsal plate of phytoseiid mite
dissection of Orius
PRODUCTION OF NATURAL ENEMIES:
RESEARCH CHALLENGES
• The development of artificial diets is not about nutrition
alone. The complexity of designing these media requires
expertise from different disciplines
• We need to improve our understanding of the nutritional
physiology and ecology of arthropod natural enemies,
including interactions with their hosts and micro-organisms
• Food processing technology may greatly advance the
development of insect diets. Equipment needs to be
further developed for large-scale diet preparation and
packaging (e.g., extruder applications)
• More attention needs to go to the development of effective
artificial living and oviposition substrates
• Quality control and quality assurance are important
considerations for the mass production of natural
enemies: “Will they work in the field?”