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abundance of pollen attached to a bee was recorded. Pollen 40-50 C compost was significantly reduced as compared to that concentration was not correlated to acquired Ice-minus population in media prepared with higher or lower temperature composts. densities. Bees acquired Ice-minus strains, non-nucleating Humicola isolates, unable to grow on PDA at 25 C, specifically bacteria, and Ice-plus bacteria from strawberry blossoms. The reduced efficacy of the biocontrol agent in paired biocontrol prevalence of strain GJP17BR2 on bees as compared to RGP36R2 was radish bioassays. Population development of T. hamatum 382 or inversely related to their relative population densities on of Rhizoctonia solani in media prepared with composts from blossoms from the same sampling period. Among the various temperatures did not differ. Results suggest that interpretations of this observation is the possibility that the compost process temperature impacts performance of Trichodermatwo strains may occupy spatially distinct habitats on strawberry fortified composts. blossoms that are reflected in the foraging habits of bees. 134 138 INDUCED SYSTEMIC RESISTANCE TO PERONOSPORA TABACINA IN TENNESSEE 86 TOBACCO AND TISSUE CULTURE REGENERANTS OF INDUCED PLANTS. E. M. Nuckles and J. Kuc. Department of Plant Pathology, University of Kentucky, Lexington, KY 40546. INCREASE OF SCLEROTINIA SCLEROTIORUM AND VERTICILLIUM DAHLIAE FOLLOWING CERTAIN FOLIAGE FUNGICIDE SPRAYS ON POTATO. Gene 0. Easton, Washington State University, Irrigated Agriculture Research and Extension Center, Prosser, WA 99350. The tobacco cultivar Tennessee 86 is resistant to tobacco etch virus and tobacco vein mottling virus but is highly susceptible to tobacco mosaic virus and to blue mold caused by f. tabacina. Stem injection with sporangiospores of P. tabacina induced systemic resistance to blue mold in Tn 86. Resistance was expressed as a reduction in number, size, and sporulation of lesions. Tissue culture regenerants of Tn 86 plants steminjected with P. tabacina were protected against blue mold compared to regenerants from plants stem-injected with water. Induction of systemic resistance may provide a technology for rapidly introducing resistance to plants resistant to one or more pathogens. 135 Fungicides were sprayed on potato foliage in plots infested with Colletotricum coccodes (Cc), Sclerotinia sclerotiorum (Ss), and Verticillium dahliae (Vd). Visual ratings of symptoms and laboratory propagule counts after culture from stems showed: 1) Sclerotinia stem rot was not different from the control in plots sprayed with vinclozolin and thiophanate methyl in 1986-1988, 2) Sclerotinia stem rot was 5- to 10-fold greater in 1987 plots sprayed with chlorothalonil or Bravo C/N and their combination and in 1988 plots sprayed with chlorothalonil or fentin hydroxide and their combination than the control, 3) significantly more visible microsclerotia and stem propagules of Vd were present in 1988 plots treated with chlorothalonil or fentin hydroxide than in control plots, and 4) Cc was not reduced or enhanced by any spray treatment. Application of fungicides did not alter tuber yield. FIELD PERFORMANCE AND GREENHOUSE ASSAY OF FUNGI FOR BIOCONTROL OF RESIDUE-BORNE PYRENOPHORA TRITICI-REPENTIS. W. F. Pfender, W. Zhang, and A. Nus. Dept. of Plant Pathology, Kansas State University, Manhattan, KS 66506. Candidate biocontrol fungi (grown in bran/millet seed culture) were applied to field plots containing Pyrenophora-infested winter wheat straw, with the goal of reducing ascocarp (primary inoculum) production by the pathogen in the residue. Limonomyces reduced ascocarp production by 86% and by 60-80%, respectively, in two years of field tests. Among fungi tested in one year only, an unidentified fungus significantly reduced ascocarp production, Laetisaria gave inconsistent results, and several fungi were ineffective. To screen candidate biocontrol fungi which under Pyrenophora-infested controlled conditions, straws a are method inoculated was developed with test in fungi and placed on a greenhouse bench with intermittent wetting cycles. Test conditions (straw and inoculum types, wetting periods) have been adjusted to give results consistent with those in field teats with selected fungi. 136 139 PROTECTION OF POTATO FROM RHIZOCTNIA-CANKER WITH BINUCLEATE RHIZOCTONIA-LIKE FUNGI. A. Escande and E. Echandi, Department of Plant Pathology, North Carolina State University, Raleigh, 27695-7616. Fourteen isolates of binucleate Rhizoctonia-like fungi (BN wer t e d as of bincl te agent s f ungiot BURo were studied as potential biocontrol agents for protection of potato from Rhizoctonia-canker in greenhouse and potato fields naturally infested with Rhizoctonia solani (AG-3). Eight of the BNR reduced incidence and severity ofi reoctonia-canker by an average of 78 and 85%, respectively, in greenhouse experiments. In severity the field, of Rhizoctonia-canker six of the eight BNR by an reduced average incidence of 43 and and 41%, respectively. In a field heavily infested with R. solani, selected BNR and the fungicide Ttps 2.5D (thiophanate methyl) were equally protective of potato from Rhizoctonia-canker. Cultivars Burbank, Atlantic, Irish and Cobbler, Superior Kennebec, Norchip, were Russet equally protected from Rhizoctoniacanker by selected BNR under field conditions. Isolates of BNR have potential as biocontrol agents for protection of potato from Rhizoctonia-canker. COMPATIBILITY OF SOME COMMONLY USED SOIL DRENCH FUNGICIDES AND INSECTICIDES WITH THE BIOCONTROL AGENT GLIOCLADIUM VIRENS. J. C. Locke and R. D. Lumsden, Florist and Nursery Crops Lab. and Biocontrol of Plant Diseases Lab., Plant Sciences Institute, USDA-ARS, Beltsville, MD 20705. The interaction of the biocontrol agent Gliocladium virens with fungicides and insecticides, which can be used as soil drenches in bedding plant production systems, was investigated. The pesticides tested included: Aliette 8OW, Banrot 40WP, Benlate 50W, Subdue 2E, Terraclor 75W, Truban 25EC, Diazinon AG4E, and Vydate L. The pesticides were evaluated for their effect on both proliferation of G. virens and the degree of damping-off control achieved against Pythium ultimum and Rhizoctonia solani on zinnia seedlings. None of the pesticides evaluated, except Benlate applied prior to introduction of the biocontrol agent, altered proliferation of the biocontrol agent in a soilless growing medium. Similarly, none of the pesticides decreased nor increased efficacy against either Pythium or Rhizoctonia. These results demonstrate the compatibility of this biocontrol agent with these pesticides at their labelled application rate. 137 INTERACTIONS BETWEEN TRICHoDERMA HAMATUM AND THERMOPHILIC FUNGI IN BARK COMPOST IN SUPPRESSION OF RHIZOCTONIA DAMPING-OFF. Y. R. Chung and H. A. J. Hoitink, Dept. of Plant Pathology, Ohio State Univ., Wooster, OH 44691. 141 EFFECTS OF DE-W TEMPERATURE, DEW PERIOD, AND REPEATED A white zone of microbial growth typically is present in compost piles where process temperatures range from 40-50 C. Humicola spp. were the predominant fungal taxa isolated from this zone. The ability of Trichoderma hamatum 382 to induce suppression to Rhizoctonia damping-off in media prepared with INOCULATIONS WITH PUCCINIA JACEAE ON YELLOW STARTHISTLE. A. R. BENNETT and W. L. BRUCKART, USDA-ARS, Ft. Detrick, Bldg. 1301, Frederick, MD 21701. Puccinia jaceae was evaluated for biological control of yellow starthistle (YST, Centaurea solatitialis) in greenhouse 1152 PHYTOPATHO LOGY
studies. YST plants were uniformly inoculated with uredinio- resulting from biotic activity, was assayed by comparing spores 4 wk after planting and placed in dew chambers for 4, survival of Pratylenchus penetrans (PP) in raw (R) and sterile 8, 12, or 16 hr at temperatures ranging from 10 to 30 C. (S) soils. PP were added to 100-g samples of orchard soil Disease severity (number of pustules) was evaluated 2 wk after (cherty silt loam) and incubated at 25 C. Percent recovery of inoculation, and the most pustules (1.6/cm 2 leaf area) viable PP was lower (P=0.05) in R than in S soils after 11 developed after incubation at 20 C for 12 or 16 hr. No days of incubation. This difference in percent recovery was infection occurred at 10 or 30 C. Inoculation of YST plants greater at 20 than at either 14 or 30% soil moisture, and up to four times on a weekly basis beginning 4 wk after increased as initial inoculum was increased beyond 200 PP. planting resulted in mean shoot biomass values of 0.88, 0.60, This assay was used to evaluate NBA stimuiation by the 0.52, 0.46, and 0.41 g for 0, 1, 2, 3, and 4 inoculations, nematicide Clandosan. Mean percent recovery was significantly respectively. Under suitable conditions, significant lower in R amended with 22-g of Clandosan per L (0%) than in reduction of YST biomass can occur from infection by P. jaceae. unamended R (17%), and, in Clandosan-amended S (16%) than in unamended S (33%). The results of this assay are inconsistent with an enhanced NBA mode of action for Clandosan. 146 PREVENTION OF AFLATOXIN CONTAMINATION WITH STRAINS OF ASPERGILLUS FLAVUS. P. J. Cotty, USDA, ARS, Southern Regional Research Center, P.O. Box 19687, New Orleans, LA 70179. Cottonseed can be infected by strains of Aspergillus flavus Link that do not produce aflatoxins. Furthermore, virulence of the fungus is not correlated with aflatoxin production. These observations suggest that strains of A. flavus which do not produce aflatoxins may exclude other strains from crops and prevent aflatoxin contamination. Greenhouse studies confirmed that non-toxigenic strains of A. flavus can prevent aflatoxin contamination of cottonseed by toxigenic strains. When simulated exit holes of the pink bollworm were inoculated with a strain which did not contaminate cottonseed with aflatoxins, subsequent contamination of developing cottonseed by two toxigenic strains was prevented. Inoculation with toxigenic and non-toxigenic strains simultaneously resulted in at least 100 fold reductions in toxin contamination. Non-toxigenic strains may be useful as protective agents in all susceptible crops. 143 TRICHODERMA HARZIANUM USED IN INTEGRATED CONTROL OF BOTRYTIS 147 CINEREA ROT ON APPLE. Arne Tronsmo. Department of Microbiology. POSTHARVEST BIOCONTROL OF GRAY MOLD OF PEAR BY PSEUDOMONAS Agricultural University of Norway. N-1432 Aas-NLH. Norway. GLADIOLI. G. H. Mao and R. A. Cappellini, Department of Plant By the use of the fungal antagonist Trichoderma harzianum we Pathology, Rutgers University, New Brunswick, NJ 08903. have been able to reduce Dry Eye Rot (Botrytis cinerea) on Pseudomonas gladioli and its cell-free filtrate (CFF) inhibitapple. However, we are not able to perform biological control of all other diseases and pests in commercial fruit growing, ed growth of Botrytis cinerea in vitro. The bacterium was tested in vivo for biocontrol of gray mold of Anjou pears. Integrated control with fungicide resistant antagonists is therefore of interest. By testing several Trichoderma spp. isolates for fungicide resistance, we were able to select isolates with much higher tolerange to Carboximid and other fungicides than the parent strain. One isolate, Trichoderma harzianum 220 were able to control Dry Eye Rot in a field with commercial spray program against other pest and diseases, both alone and together with reduced dosage of Vinclozolin. Even ifinerae cnro it . azinm n Vnlooinws o if integrated control with T. harzianum and Vinclozolin was not significantly more effective than biological control on its own., the combination of two different control methods will probably give safer control, and less danger of resistance development in the pathogen. Bacterial suspensions were applied to wounded pe rs. ýhe pears were then inoculated with B. cinerea (5x10 -5x10 /ml) 1 hr later and incubated for 7-9 days in a moist ghamber at 23-25 C. P. gladioli at concentrations of 1xl0 ) colony-form- ing units/rl (CFU/ml) retarded disesse development on pesrs challenged with B. cinerea spor e suspensions. When the antagonist was appliedat Ixi0 CFU/ml, the pathogen did not produce lis onpears. Contr l of g ay hold was not produce lesions on pears. Control of gray mold was not obtained on wounded pears applied with CFF at concentrations of 20-80 units/ml at the same pathogen inoculum levels. 144 BIOLOGICAL AND CULTURAL MANAGEMENT OF ROOT INFECTING FUNGI. Brad Melvin, Joe Vargas, Jr., Lee Berndt and Ron Detweiler. Dept. of Botany and Plant Pathology, Michigan State University, East Lansing, Michigan. 45823. Management of necrotic ring spot, a disease caused by an ectotrophic root infecting fungus (Leotosohaeria korrae), was obtained on Poa pratens~is receiving daily irrigation and/or bioorganic fertilizer treatments. Highly significant reduction of necrotic ring spot was achieved with a 2.5mm per day irrigation treatment compared to an 80% evapo-pan irrigation treatment or no supplemental irrigation treatment. Significantly less disease incidence occurred with the bio-organic fertilizers, Turf Restore and Sustane in the 80% evapo-pan irrigation treatment compared to the untreated control. A correlation between disease reduction and an increase in total thatch bacterial populations in daily irrigated plots during May and June was observed. The early season period of turf growth is the optimum time of year for infection of . Drtni by L- kore Total bacterial populations were higher throughout spring and early summer in the Turf Restore and Sustane plots compared to the untreated control. Many of the bacteria in these studies are antagonistic to I- kora in vitro. 148 Withdrawn 149 145 CLONING OF THE BETA-TUBULIN GENE FROM BENOMYL-SENSITIVE AND A QUANTITATIVE ASSAY OF NEMATODE BIOCONTROL AGENT ACTIVITY AND BENOMYL-RESIsTANT FIELD STRAINS OF VENTURIA INAEQUALIS. ITS USE IN A CLANDOSAN AMENDED SOIL. J. C. Doney, Jr. and J. Harrie Koenraadt, S.C. Somerville and A.L. Jones, Dept. of B. Kotcon. Div. of Plant and Soil Sciences, West Virginia Botany and Plant Pathology and the Pesticide Research Center, univ., p. 0. Box 6057, Morgantown, WV 26506-6057. Michigan State University, East Lansing, MI 48824. Nematode biocontrol agent (NBA) activity, defined as mortality Widely differing levels of benomyl-resistance in Venturia Vol. 79, No. 10, 1989 1153
Page 1 and 2: Abstracts of Presentations at the 1
Page 3 and 4: Twenty Fusarium solani (Mart.) Sacc
Page 5 and 6: means used to derive them were not
Page 7 and 8: 46 A COMPARISON OF THE EPIPRE AND K
Page 9 and 10: 62 THE INCIDENCE AND IMPACT OF SPHA
Page 11 and 12: 79 83 82 SELECTION AND USE OF OXALA
Page 13 and 14: nificantly among plots but there wa
Page 15 and 16: Chrysanthemum morifolium (florists'
Page 17: anine ammonia lyase (PAL) and hydro
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Page 23 and 24: 173 177 THE EFFECT OF EXPRESSION OF
Page 25 and 26: shown to be double-stranded circula
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Page 29 and 30: Spatial patterns of disease were st
Page 31 and 32: 236 240 INDUCTION OF RESISTANCE TO
Page 33 and 34: y suppression of Mn oxidizers in th
Page 35 and 36: Colbaugh. Texas Agricultural Experi
Page 37 and 38: 284 BASELINE-SENSITIVITY OF THREE P
Page 39 and 40: Department of Agronomy, University
Page 41 and 42: 316 SEROLOGICAL NONIDENTITY OF IRIS
Page 43 and 44: amended with 25 g/L of KC1O Prelimi
Page 45 and 46: lacZ gene fusions have been used to
Page 47 and 48: Department of Plant Pathology, Univ
Page 49 and 50: causative agent of greening, howeve
Page 51 and 52: and chitosan heptamer will be discu
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Page 55 and 56: M. Laakso and J. W. Moyer, Dept. of
Page 57 and 58: 443 The stability of antigenic dete
Page 59 and 60: seed decay by 10%. Phomopsis seed d
Page 61 and 62: LARYAFD, QMKAA, FGLDG and TERH, in
Page 63 and 64: In an initial survey of ten commerc
Page 65 and 66: The primary cell walls of grasses c
Page 67 and 68: 523 AVIRULENCE OF WHEAT LEAF RUST T
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the reasons for the late observance
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verified. A translocation linked to
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587 591 MEASURING VIRULENCE ASSCIAT
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603 PHYSICAL CHARACTERIZATION OF MU
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agar diffusion tests and spore germ
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Spring beauty latent virus (SBLV) h
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SOYBEANS. Barry M. Cunfer and Juju
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666 670 COMPUTER-ASSISTED WHITE MOL
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682 PHYTOPHTHORA CINNAMOMI. Univers
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698 SCREENING OF VESICULAR-ARBUSCUL
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