Tritrophic interactions in soil

Transcription

1 Tritrophic interactions in soil 2 examples Rob van Tol & Willem Jan de Kogel Vine weevil plant parasitic nematode Grubs plants entomopathogenic fungi hemical information in soil: tritrophic interactions between plants, insects and parasitic nematodes Field situation summer and winter Rob van Tol International Rob Marleen vplant Riemens Research Frans International Zoon Rob Marleen Riemens Willem Jan de Kogel Frans Zoon Willem Jan de Kogel AUniversity of Amsterdam Pim University de Voogt of Amsterdam Pim André de Voogt van Roon André van Roon Maurice Sabelis Maurice Sabelis an Tol Thuja and Taxus; host plants Otiorhynchus sulcatus; infected larva Otiorhynchus sulcatus; larvae Heterorhabditis megidis 1

2 /18/2011 ontrol efficacy EPN Methods: Y tube Efficacy in practice (autumn application) ontrol results in pots: high and predictable (80 100%) ontrol results in the open field: variable and unpredictable Drench with 1 million EPN/m 2 gives 60 70% control in field tests in the Netherlands A2 (60 ml) A1 (60 ml) B1 (60 ml) B2 (60 ml) How to improve efficacy? >>Understand host finding behaviour (120 ml) Preference of H. megidis for herbivory damaged roots Preference of H. megidis for herbivory damaged roots weevil-damaged Thuja mechanically-damaged Thuja blanco (L) blanco (R) preference of responding nematodes (%) Thuja Taxus Fragaria control weevil-damaged roots n.s preference of responding nematodes (%) (Ecology Letters (2001) 4: ) 2

3 S.O.S. signalling of roots Exploitation of signals in soil EPNs Quality control of product prior to application Selection for strains: searching and genetics Hellup! Help!! Hellup! Help!! Aanvalluh charge General Preventive attraction of natural enemies towards roots for plant protection More effective use of introduced antagonists Attraction and repellence of grubs in soil systems as part of pest control strategies The cockchafer Melolontha melolontha example Rob van Tol Gerrie Wiegers Willem Jan de Kogel 3

4 Life cycle Pest problem White grubs Where?: Pasture, Nurseries, Fruit, Forest, Vineyards Damage?: Grubs live several years in soil eating roots Problem?: hemical means : Biological means but relative expensive, large areas, application difficult, limited efficacy, legal registration in EU difficult M. melolontha lives up to 3 years in soil as a grub Metarhizium anisopliae ontrol strategies Adults Pheromones Light traps soil cover Grubs insecticides entomopathogenic nematodes entomopathogenic fungi bacteria (milky spore disease:bacillus sp.) rickettsia (Rickettsiella popilliae) parasitoids (Dexia rustica) Beauveria brongniartii Heterorhabditis sp. Dexia rustica H. megidis Research strategies Lure and kill attractive plants luring grubs to effective control means Push and pull repelling plants protecting crop attractive plants as alternative food control of grubs on lure plants (removal, insecticide, biocontrol) above and belowground Repelling adults from oviposition sites (repelling plants) and grubs from plant roots B. popilliae 4

5 Olfactometer + plant selection Pasture grasses and herbs 14 species over crops Tagetes Brassicaceae rops to be protected Taxus, Quercus, Fagus, arpinus,... Efficacy testing biological means Nematodes EPN strain selected for M. melolontha (coded) Fungi Beauveria brongniartii commercial strain Beauveria bassiana commercial and other strains Metarhizium species `brunneum`, `guizhouense`, `robertsii`, `flavoviride`, `anisopliae`,... Others Bacillus sphaericus, B. popilliae, B. thuringiensis, Paenibacillus sp. Bioassays behaviour (not effective) Bioassay behaviour (effective) T olfactometer PRI 2 (PV) 80m m A B D E F A 135mm B D 135mm E F view from above 100mm = release site A and F: connections to plant tubes Gauze in bottom of plant tubes to prevent root larvae contact 5

6 Bioassays biological means Results efficacy means (L3 stage grubs) % mortality control ERL 700 F001 Met52 F62 GHA B.brong EPN x days after application % mortality Results efficacy means (L3 stage grubs) control F52 BS IP601 a-22 IP609 IP560 IPO-87 IP564 IP618 IPO-Dr B.popilliae a-1 IP608 B.brongniartii Rhizosphere growing Metarhizium isolates tested IP608 as effective as B. brongniartii days after application Results plant preference grubs ( ) Analyzed for attraction control testplant TaxusX media Fagus sylvatica Quercusrobur Lolium multiflorum Festuca rubra Trifolium repens Daucus carota Taraxacum officinale respons (%) of grubs tested 6

7 Results plant preference grubs ( ) Analyzed for repellence control+no respons testplant TaxusX media Festuca rubra Results plant preference grubs ( ) Taraxacum officinale Analyzed for attraction TaxusX media Fagus sylvatica Quercusrobur testplant Tanacetum vulgare Daucus carota Lolium multiflorum Festuca rubra Trifolium repens Taraxacum officinale Daucus carota respons (%) of grubs tested respons (%) of grubs tested Results plant preference grubs ( ) Analyzed for repellence T. officinale+no respons testplant Results: beech without repellent plants TaxusX media Festuca rubra Tanacetum vulgare Daucus carota respons (%) of grubs tested 7

8 Results: beech with repellent plants ontinuation repellent strategy Large field tests in reforestation areas in Poland Effect on grubs present Prevention of migration grubs into fields Push pull with attractive alternative (carrot, dandelion, grass, other..(tests in NL) Effect of cover crop on egg laying beetles Rhizosphere ompetence of M. anisopliae Most previous work with entomopathogenic fungi has ignored the habitat preferences and survival of the fungus outside of the host. It is possible that factors associated with fungal biology outside of the host are more important when selecting an isolate than how pathogenic it is against a particular host in a laboratory bioassay. Efficacy of Rhizosphere olonized Roots 76% of black vine weevil larvae feeding on fungal treated roots were dead after 2 weeks 8

9 Metarhizium persistence on Picea abies Results plant preference grubs (2010) 3.00E+07 Tests performed with plants only 1 week before inoculated with spores 2.50E+07 N=20 Plant =Daucus carota Fungus =Metarhizium anisopliae IP608 ontrol FU/g dry soil 2.00E E E+07 F52 Bulk Media F52 Rhizosphere 285 Bulk Media 285 Rhizosphere 99 Bulk Media 99 Rhizosphere P+F P+F F P 5.00E+06 P E+03 respons (%) of grubs tested Weeks Post Planting Results plant preference grubs (2010) Tests performed with plants only 1 week before inoculated with spores N=20 Plant =Daucus carota Fungus =Beauveria brongniartii lbu ontrol Prevalence and Isolate Identification Strawberries, blueberries, wine grapes, hristmas trees F P+F P Which fungi are present and how prevalent are they? P P+F respons (%) of grubs tested Isolates more inherently suitable for use as a rhizosphere colonizer? Fisher, Rehner and Bruck Journal of Invertebrate Pathology In Press 9

10 Rhizosphere ompetence: A New Approach??? The percent of blueberry, hristmas trees, grape and strawberries samples collected from fields throughout the Willamette Valley, OR colonized by four Metarhizium taxa and nine Beauveria taxa. Plant host range (Underway) Persistence (5 yr study underway) olonization of elongating roots (Underway) Efficacy (Underway) ompatibility with other biologicals Main questions Main scientific questions What is the role of rhizosphere competent fungal entomopathogens in regulating pest populations? How can we use and implement this for more effective microbial control programs? Do plants benefit from the association? Is the `bodyguard` concept relevant in soil? What mechanism? Have different phylogenetic groups different strategies in association with plants? 10

11 Main applied questions Most effective approach for inoculation roots? Persistence on root systems of different plant species? Will it provide consistent and acceptable levels of pest control? Are there fungal species with wide range of host plants and target pest insects? ontinuation options Screening/selection entomopathogenic fungi NL/USA (Biocontrol companies, PRI, USDA) Rhizosphere competence/persistence Efficacy against target pests Host plant range Olfactory preference/acceptance fungus plant by grubs (PRI, USDA) Fungus induced plant attraction (RU Nijmegen, PRI) Yes/no present for selected fungus plant combinations hemical identification Detection infested plants (grubs/fungi/... via top soil odour profile) Existing/planned cooperation Research University of Berlin Germany (Prof. Dr. M. Hilker and E. Eilers) Max Planck Institut for hemical Ecology Jena Germany (Dr. A. Reinecke) Radboud University Nijmegen (Prof. Dr. N. van Dam, Dr. S. ristescu) Forest Research Institute Poland (Dr. Sukovata) USDA USA (Dr. D. Bruck) Research Stations Netherlands Biocontrol companies... The project `Interactions between soil pests, crop and biological means` is part of the BO program Plant Health financed by the Dutch ministry of Agriculture 11