Meso- and Macrofauna Lecture
CSS 360
Fall 2011
Soil fauna and suppression of plant pathogens
• Collembola (springtails) are enhanced by green manures and
in turn regulate pythium in sugar beets and suppress
Rhizoctonia “root killer” stem canker in potato
• Springtails rapidly consume Fusarium and Rhizoctonia,
reducing spores of Fusarium by 92%
Fusarium
Rhizoctonia
Pythium blight
Lions of the microbe zoo:
Mites and Nematodes
Representation of detrital food web in shortgrass prairie. Fungal-feeding mites
are separated into two groups (I and II) to distinguish the slow-growing
cryptostigmatids from faster-growing taxa. Flows omitted from the figure for the
sake of clarity include transfers from every organism to the substrate pools
(death) and transfers from every animal to the substrate pools (defecation) and
to inorganic N (ammonification).
Overview – Arthropods in the soil
• Arthropods in a square mile of crop land:
– Several dozen species
• In a square mile of forest soil:
– Several thousand species
•
MOST soil dwelling arthropods eat fungi, worms, or other
arthropods
– Root feeders and dead plant shredders are less abundant
• As they feed arthropods mix and aerate the soil, regulate the
size of other soil organisms, and shred organic matter.
Arthropods such as mites
200 species of mites in this microscope view were extracted from one
square foot of the top 2 inches of forest litter and soil
Role: Important in nutrient cycling and predation
Microshredders; here immature oribatid mites skeletonize plant leaves
Nematode abundance in 3 organic inputs and 3
farming intensities
Seasonal average of plant available N
during the 2004 growing season in three
farming/mgmt intensities and 3 organic
inputs
Seasonal means of nematode
trophic abundance
Why do you think plant parasite abundance decreases at intermediate intensity?
3 ecological groups of earthworms
Endogeic example:
Aporrectodea
caliginosa (angle
worms)
Epigeic example:
Lumbricus rubellus (leaf
worms)
Anecic example:
Lumbricus terrestris
(nightcrawlers)
Earthworm Anatomy
•
•
•
•
Cold-blooded
Invertebrates
No eyes (Light sensitive)
Breathe through skin
-Can live underwater
•Feel vibrations through ground
•Setae= bristles for moving
•Can regrow tail
•Mucus secretion
–Create stable tunnels
Earthworm Effects on Soil Functions
• Promote aggregation and alter soil structure and water
dynamics
• Mix soil and redistribute nutrients
• Alter microbial communities, stimulate microbial activity
• In forest, can dramatically change litter and duff layers, may
have a long-term effects on plants
• Enrich soil through castings and digestion
– Casts = several tonnes / acre / yr
Thick layer of duff and litter in a
forest without worms
Thin layer of litter and no duff in a
forest with earthworms
Earthworm addition markedly increases both large and small macropore abundance
Pore generation also a function of residue…why?
Earthworm Community Dynamics
• Disturbance decreases earthworm abundance (e.g. tillage)
• Residue type influences abundance (corn vs. soybean)
• Soil amendment (e.g. manure) influences abundance
Macroarthropods
Includes spiders, termites, ants, beetles and others
Body lengths from 10 mm to 15 cm (centipede)
Many are transient or temporary soil residents
Most are litter feeders but some eat microarthropods and other organisms or weed
seeds (beetles)
Churn, mix, and move soil
termite mound
scarab beetle
ant mound
Energy Flow in a Grassland Model
The Decomposer Subsystem
Consumption - Excretion = Assimilation - Respiration = Production
DECOMPOSER SUBSYSTEM
Decomposers+detritivores
microbial decomposers
136.4
invertebrate detritivores
15.2
Microbivores
invertebrates
10.9
Carnivores
vertebrates
0.04
invertebrates
0.65
TOTAL
192.
0
- 12.1
=
=
136.4
3.1
-
7.6
=
3.3
-
0.01
0.13
=
=
0.03 0.52 -
- 35.
=
157.
- 81.8
- 1.8
=
=
54.6
1.3
2.0
=
1.3
0.029
0.36
=
=
-
- 99.
0.001
0.16
=
58
Calculated consumption, assimilation, egestion, production and respiration by
heterotrophs per 100 J m-2 net annual primary production in a hypothetical grassland
community (after Heal & MacLean, 1975 in Begon et al. 1986).
Case study of bio-control
Japanese beetles are a widespectrum pest: in large
numbers the grubs chew on
grass roots, and the adults
shred flowers (roses, hibiscus)
and contaminate blueberry
A range of biocontrol options are
available
Japanese beetle life cycle
•Soon after emergence, beetles mate
• Females seek moist, well maintained
areas of turf to deposit their eggs.
•Eggs are laid in the upper 2 to 3 inches of
the soil
•40 to 60 eggs laid over a 30- to 45-day
lifespan
•Grubs grow and emerge the following
season
Dry soil will stress the beetle
Natural microbial control
• Japanese beetle grubs are infected by
many species of bacteria, fungi,
protozoans and nematodes – these are
providing control!
• Michigan is a new area for Japanese
beetle, natural control is not always
well established
Biocontrol options
Microbe control
• Milky disease (Bacillius popilliae)
• B.t. strains (Bacillius thuringensis)
Macroorganism control
• Parasitic wasps and flies
• Parasitic nematodes
• Trap crops
Trap crops
• Border of plants attractive to Japanese
beetle (cocklebur, evening primrose, dwarf
mallow), additional control is required
• Toxic and attractive plants are best as trap
crops: Castorbean and Bottlebrush
Biocontrol of white grubs
(e.g., Japanese beetle)
Biocontrol:Heterorhabditis
bacteriophor (Hb) (parasitic
nematodes)
Biocontrol - Slow to establish
but BROADSPECTRUM
• Application: Nematodes can be effective on 200
plus soil-dwelling pests, once established
• Research continues to find strains that work
particularly well on a particular
pest. Heterorhabditis bacteriophor Hb are the
best for controlling beetle grubs.
Nematode bio-control: variable
results
• BioSafe, BioVector commercial names
for Steinemema carpocapsae
(nematode)
• Wide range of effectiveness (cool soil
temperatures at application or poor
product quality are two problems)
Effective example:
Milky spore
• Easy to apply, effective in areas with long
summers/warm soil periods (less in NE)
• Not compatible with insecticides, because an
insecticide will kill the host, the grubs (some grubs
need to be present for milky spore to spread and
establish)
• May require a 2 to 4 year establishment period
• Once established will provide broadspecturm
control of many grubs over the long-term (20 or
more years)
Blueberry ground cover
• Grass centers are a host for Japanese beetles
• Replace grass between blueberry rows with
clover
– Challenges: acid soil, vigorous ground cover needed
to compete with weeds and prevent erosion
Wasp and Fly Parasites of JB
• The most effective wasp parasites are the Tiphia
wasps.
• Introduced from Japan, Tiphia popilliavora, and
Korea, T. vernalis, these species attack the grub
stage in thatch or soil.
• The only major adult Japanese beetle parasite is
a fly imported from Japan, Istocheta aldrichi
Summary - Japanese beetle
control:
• Know the life cycle – control the grub or
adult (most control focuses on juvenile
stage)
• Find parasites or predators to control
• Use micro or macro organisms, and the
combination
• For exotic pests such as JB, search for
biocontrol agents in home region
Biology and management of
nematodes on turfgrass
• Damage caused by: dagger (Xiphinema spp),
root knot (Meloidogyne spp), stubby root
(Trichodorus)
• In a typical golf course liter of soil: 50 to
33,000 root knot nematodes found
• California challenge: Anguina pacificae
Assessment of nematode control in Calif.
golf courses
(Westerdahl et al., 2006)
• Digital images used to assess golf
course grass color
• Visual inspection by experienced
supervisors also ranked turf quality
• Poa annua greens
Nematicides gave moderate to
nil control
Biocontrol studies underway
Overview of biological
control approaches
• Three general approaches to biological
control
– Importation, augmentation and
conservation of natural enemies.
– Each of these techniques can be used either
alone or in combination in a biological
control program.
Biocontrol agent and host
cycles
________ Control agent population
________ Pest (host) population
Economic threshold for host
population
Summary - Biological control
• Predation, Parasitism
• Background ‘natural control’: species of bacteria,
fungi, protozoans and nematodes
• Importation, augmentation and conservation of
natural enemies
• Plants (diverse borders and economic crop
species) can play an important role
• Future? Genetic engineering augmentation of
microorganisms
Reading
• Crow.pdf on website
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•
•
•
“Lab Report #3” on website
New Schedule on website
No Class Wednesday
Monday will be final lecture
– “Synthesis of course material”