Poster Abstracts:

Poster 1. Biocontrol mechanisms of Pseudomonas aeruginosa PNA1 and its Tn5-Derivative against Fusarium wilt and Pythium damping-off. Vanamala Anjaiah (1,2), Nico Koedam (2), Brian Nowak-Thompson (3), Joyce E. Loper (3), Monica Hofte (4), James Tabi Tambong (4), and Pierre Cornelis (1). 1. Laboratory of Microbial Interactions, Flemish Interuniversity Institute for Biotechnology; 2. Department of Plant Physiology, Vrije Universiteit, Brussel, Paardensraat 65, B-1640 Sint Genesius Rode, Belgium; 3. US Department of Agriculture, Agricultural Research Service, 3420 N. W. Orchard Avenue, Corvallis, Oregon, 97330 USA; 4. Laboratory of Phytopathology, University of Gent, Coupure Links 653, B-9000, Gent, Belgium. Fluorescent pseudomonads were shown to be involved in biocontrol of soil-borne diseases caused by root pathogens such as Pythium sp., Fusarium sp., Sclerotium sp., Macrophomina sp. Several mechanisms have been described for fluorescent pseudomonads to explain the suppression of root pathogens in vivo and in vitro such as excretion of high-affinity siderophores, production of antibiotics, hydrogen cyanide and lytic enzymes. Pseudomonas aeruginosa PNA1, isolated from the rhizosphere of chickpea in India, inhibited in vitro mycelial growth of different phytopathogenic fungi including those mentioned above by the production of phenazine-1-carboxylic acid (PCA) and oxychloraphine (OCP). Strain PNA1 also protected the chickpea plants from Fusarium wilt disease caused by Fusarium oxysporum f. sp. ciceris. Two mutants deficient in phenazine production were obtained following transposon mutagenesis of PNA1, one with an insertion in the phnA gene coding for a second anthranilate synthase involved in phenazine biosynthesis, the other one in trpC gene coding for indole glycerol phosphate synthase involved in tryptophan biosynthesis. Consequently, the last mutant could not grow on minimal medium in the absence of tryptophan, and additions of high concentrations of the amino acid restored its capacity to produce PCA and OCP. Neither phnA mutant nor trpC mutant suppressed Fusarium wilt of chickpea and pigeonpea to the level achieved by the wildtype strain, indicating that phenazine production contributed to the biocontrol of this disease by PNA1. The trpC mutant accumulated anthranilate in the medium and was still able to inhibit growth of Pythium sp. Anthranilite, an intermediate in the phenazine and tryptophan biosynthesis pathways, was confirmed to be a potent anti-Pythium molecule and evidence is shown that it can be used to control Pythium-induced damping-off in horticultural crops.

Poster 2. Formulation, production, and shelf life of granular bioherbicides. W. J. Connick, Jr.(1), D. J. Daigle (1), M. A. Jackson (2), C. D. Boyette (3) and K. P. Hebbar (4). 1. Southern Regional Research Center, ARS, USDA, P.O. Box 19687, New Orleans, LA; 2. NCAUR, ARS, USDA, Peoria, IL 61604, SWSL; 3. ARS, USDA, Stoneville, MS 38776; 4. BPDL, ARS, USDA, BARC-W, Beltsville, MD 20705. Improved formulation technology is needed to preserve the viability of fungal weed pathogens in products with commercial potential. Shelf life of granules containing matrix-encapsulated inocula of Fusarium oxysporum, a pathogen of coca, and Colletotrichum truncatum, a pathogen of hemp sesbania exceeded one year at 25^oC. Factors that promoted increased shelf life were water activity (a_W) of the product and choice of fungal inoculum type, such as naturally-stable chlamydospores of F. oxysporum or microsclerotia of C. truncatum. Additionally, encapsulation in a matrix protected the inoculum throughout processing and storage. The matrix chosen was composed of wheat flour and kaolin, and the granules are called ‘Pesta’ because of the pasta-like process that is used. The wheat flour component provided nutrients for proliferation of the fungal bioherbicide agent. Pesta granule production is now in the pilot plant stage using twin-screw extrusion and fluid bed drying equipment.

Poster 3. Host plant effects on egg masses of the spotted fireworm and parasitism by endemic Trichogramma minutum. Robin J. Stuart and Sridhar Polavarapu, Blueberry and Cranberry Research Center, Rutgers University, Chatsworth NJ 08019 USA. The spotted fireworm, Choristoneura parallela (Robinson) (Lepidoptera: Tortricidae), produces two generations each year in New Jersey cranberry bogs. It lays eggs in compact, single-layered masses of a few to over 300 eggs on the leaves of various plant species, and is often parasitized by the endemic generalist egg parasite, Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae). We examined 1789 egg masses from 17 plant species that were derived from 12 field samples taken from three managed cranberry bogs (one sample per generation per bog each year for two years). Egg masses varied in size, shape, and density (number of eggs per unit area within masses) across samples and plant species. Egg masses on narrow leafed species (e.g., redroot, swamp candles, and grasses) tended to be longer and narrower than those on broad leafed species (e.g., brier, red maple, leatherleaf, marsh St. John's wort, and marsh fern). Relatively few eggs per mass on certain plant species (e.g., marsh fern) indicate possible host preferences, whereas differences in the density of eggs in egg masses on different plant species indicate additional host plant influences on the structure of egg masses. We found 271 egg masses (15.1%) parasitized by T. minutum on 12 plant species that included the 11 most common spotted fireworm host plants. Only 11 egg masses were completely parasitized (4.1%). Parasitized egg masses tended to have fewer eggs and lower density than nonparasitized egg masses, but did not differ in length, width, area, or circumference. T. minutum exhibited an apparent preference for egg masses on sweet pepperbush and marsh St. John's wort over those on leatherleaf, but this preference was not associated with any apparent differences in the egg masses on these plant species. These results indicate potentially complex tritrophic interactions between this moth, various host plants, and T. minutum. Differential parasitism of egg masses with different characteristics and on different host plants is an important consideration for developing and monitoring biocontrol programs using this parasite

Poster 4. Biological Control Implementation Activities at the Niles Plant Protection Center (USDA, APHIS, PPQ) in Niles, Michigan. William C. Kauffman, USDA, APHIS, PPQ, Niles Plant Protection Center, Niles, Michigan. The Niles Plant Protection Center in Niles, Michigan is a USDA, APHIS, PPQ laboratory which specializes in biological control, using predators, parasitoids and pathogens to control pest insects and weeds. Projects past and present include cereal leaf beetle, Japanese beetle, gypsy moth, purple loosestrife, alfalfa weevil, Russian wheat aphid, pine shoot beetle, euonymus scale, Mexican bean beetle and karnal bunt. The Niles Center does the following: (1) Coordinates projects of local, regional and national importance; (2) Facilitates importing new natural enemies into the U.S. to solve pest problems in an environmentally friendly manner; (3) Develops rearing protocols and rears natural enemies for field release; (4) Establishes field insectaries for collecting and distributing natural enemies; (5) Conducts field surveys of natural enemies; (6) Processes field samples, including identifying natural enemies and hosts; (7) Evaluates establishment and impact of natural enemies; and (8) Educates the public and publicizes the benefits of biological control. For more information, visit the Niles web site: http://www.aphis.usda.gov/ppq/niles.

Poster 5. First Successful Inoculative Release of an Entomopathogenic Nematode Heterorhabditis bacteriophora. Parwinder S. Grewal and Michael G. Klein Department of Entomology, The Ohio State University Ohio Agricultural Research and Development Center, Wooster, OH 44691 Successful inoculation (colonization) of entomopathogenic nematodes in agroecosystems and urban landscapes may substantially reduce chemical insecticide inputs. However, due to failures in initial inoculative release attempts, current efforts with entomopathogenic nematodes focus almost exclusively on their use as innundative biological control agents with little consideration to their subsequent preservation in the environment. We report on the first successful inoculative release of Heterorhabditis bacteriophora in turfgrass on a golfcourse in the Mid-western USA. The nematodes were released on Mohican Hills golfcourse in Jeromesville, Ohio in 1986 and 1987. We re- isolated the nematodes in August 1997 from the same site and found them to be widely distributed in the rough. No insecticides had been applied to this site since nematode inoculation. Evidence of nematode recycling and effective suppression of natural populations of Japanese beetle Popillia japonica larvae was obtained. Recent replacement of broad-spectrum chemical insecticides such as chlordane with 'softer' insecticides had created an environment suitable for revisiting the inoculative release strategy for the establishment of biological control agents.

Poster 6. Sub-Lethal Effects with Acute and Chronic Exposure of Colorado Potato Beetle to the d -endotoxin of Bacillus thuringiensis. Scott D. Costa(1), George G. Kennedy, and Mary E. Barbercheck, Department of Entomology, North Carolina State University, Raleigh, NC 27695 (1) 919-515-1657 scott_costa@ncsu.edu Sub-lethal exposure of Colorado Potato Beetle, Leptinotarsa decemlineata (Say), larvae to the cryIIIA d -endotoxin of Bacillus thuringiensis var. san diego (Berliner) caused a dose dependent reduction in feeding and weight gain when tested in a leaf disc bioassay. The highest doses of chronic (continuous) exposure resulted in a peak foliage consumption on day 1 as compared to days 3-4 when exposure was acute (24 hours). Delays in development were evident only at higher doses, and were most pronounced with acute exposure because of the need to recover from intoxication before feeding and development could resume. A reduced efficiency of conversion of ingested material to biomass (ECI) probably resulted from interference with food uptake, metabolic costs for repair of midgut tissues and an increase in maintenance metabolism associated with extending development. Female adults that survived acute and chronic exposure to Bt as larvae had reduced weight, longevity and tended to produce fewer eggs (45 and 44 % reductions, respectively) when compared to control adults, which led to a decline in the net reproductive rate and (R₀) intrinsic rate of population increase (r). The lethal and most sub-lethal effects from different rates of exposure were not cumulative. Development of resistance to the toxin in a population might be delayed or accelerated by these sublethal effects, depending on the genotype of the survivors.

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