Meso- and Macrofauna Lecture

CSS 360Fall 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 mites200 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?

Epigeic example: Lumbricus rubellus (leaf worms)

Endogeic example: Aporrectodea caliginosa (angle worms)

Anecic example: Lumbricus terrestris (nightcrawlers)

3 ecological groups of earthworms

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 abundancePore 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

MacroarthropodsIncludes 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 moundant mound

scarab beetle

136.4 15.2

10.9

0.04 0.65

192.

012.1

7.6

0.01 0.13

35.

136.4 3.1

3.3

0.03 0.52

157.

81.8 1.8

2.0

0.029 0.36

99.

54.6 1.3

1.3

0.001 0.16

58

Energy Flow in a Grassland ModelThe Decomposer Subsystem

DECOMPOSER SUBSYSTEM

Decomposers+detritivoresmicrobial decomposersinvertebrate detritivoresMicrobivoresinvertebratesCarnivoresvertebratesinvertebrates

TOTAL

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).

Consumption = Assimilation- Excretion = Production- Respiration

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Case study of bio-control

Japanese beetles are a wide-spectrum 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:Heterorhabditis bacteriophor (Hb) (parasitic nematodes)

Biocontrol of white grubs (e.g., Japanese beetle)

• 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.

Biocontrol - Slow to establish but BROADSPECTRUM

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

• “Lab Report #3” on website• New Schedule on website• No Class Wednesday• Monday will be final lecture

– “Synthesis of course material”