February 6-7, 2005 - Little Rock, Arkansas
(Joint with the Southern Association of Agricultural Scientists (SAAS))
Posted online April 22, 2005
Control of Phytophthora root rot in ornamentals with cyazofamid, fenamidone and phosphite fungicides. D. M. BENSON. North Carolina State University, Dept. of Plant Pathology, Raleigh, NC 27695. Publication no. P-2005-0001-SOA.
Fungicides are an important component of IPM for Phytophthora root rot in ornamentals. Several new fungicides, including cyazofamid (Ranman), fenamidone (Fenstar), dimethomorph (Stature DM) and phosphites (Biophos and Vital) were evaluated for control of P. cinnamomi on azalea or rhododendron grown in a pinebark:sand mix. Rhododendrons ‘Roseum Elegans’ were inoculated with rice grains colonized by P. cinnamomi on 9 Jun 2004 then sprayed to run-off with fungicide. Azaleas ‘Hinodegiri’ were sprayed with phosphite fungicides 5 days before inoculation or drenched with the non-phosphite fungicides at inoculation. Fungicides were applied seven times at 14-day intervals on rhododendron, and three times at 30-day intervals on azalea. For rhododendron, none of the foliar-applied fungicides that included cyazofamid, fenamidone, or dimethomorph controlled the disease. For azalea, drenches of cyazofamid, fenamidone, and dimethomorph at 1.5, 14 fl oz and 6.4 oz/100 gal, respectively, and Biophos and Vital applied as foliar sprays at 256 and 32 oz/100 gal, respectively, gave season-long disease control.
Relative efficacy of three injection patterns of metam sodium for control of Cylindrocladium black rot in twin-row peanut. T. B. BRENNEMAN. Dept. Plant Pathology, University of Georgia, Tifton, GA 31794. Publication no. P-2005-0002-SOA.
Cylindrocladium black rot (CBR), caused by Cylindrocladium parasiticum, is a serious disease of peanut which is often treated by injecting metam sodium in the soil directly under the row prior to planting. More peanuts are being grown in twin versus single rows, raising questions regarding fumigant placement. In 2003 and 2004, injections of metam sodium (20-cm deep, 93.5 or 140.3 l/ha) were compared on twin-row peanuts either under the row (OUT), centered between the rows (MID), or putting half the rate under each row (SPLIT). In 2003, the MID and SPLIT applications reduced CBR incidence and also increased yield over the nontreated control by 659 and 1011 kg/ha, respectively. The OUT application did not reduce disease or increase yield. The 140 l/ha rate of metam sodium gave higher yield (4400 kg/ha) than the lower rate (3919 kg/ha) or the control (3452 kg/ha). In 2004, CBR was more severe and no metam sodium applications reduced disease or increased yield. Isolation frequencies of C. parasiticum from tap roots ranged from 63-86% and were similar across treatments both years.
Pathogenicity of Sclerotium rolfsii on winter wheat and peanut. V. CHOPPAKATLA (1), H. A. Melouk (2), R. M. Hunger (1), M. E. Payton (3), and K. D. Chenault (2). (1) Entomology & Plant Pathology, Oklahoma State University (OSU), Stillwater, OK 74078; (2) USDA-ARS, Stillwater, OK 74075; (3) Statistics, OSU. Publication no. P-2005-0003-SOA.
Peanut and winter wheat are occasionally rotated in Oklahoma, but the effect of this rotation on southern blight caused by Sclerotium rolfsii is not understood. Hence, greenhouse studies were conducted to evaluate the pathogenicity of six isolates of S. rolfsii obtained from peanut and wheat on cultivars of winter wheat (Jagger, 2137 and 2174) and peanut (Okrun, Tamspan 90 and Southwest Runner). Inoculations were made at two and six weeks after planting of wheat and peanut respectively, by appressing a 0.5 cm agar disk collected from a 3-day-old culture to the base of the stem. Disease assessments were made on a 1 to 6 scale, where 1 = no infection and 6 = complete death of the plant. Results indicated that host cultivar did not affect disease severity and that isolates from peanut were more pathogenic than isolates from wheat on both hosts. S. rolfsii isolates from peanut can be highly pathogenic on peanut and winter wheat, which may impact wheat-peanut rotations.
A laboratory method to determine soybean resistance to purple pod rot caused by Cercospora kikuchii. B. B. COOK and G. L. Sciumbato. Delta Research and Extension Center, Stoneville, MS 38776. Publication no. P-2005-0004-SOA.
In 2002, there was an extended period of warm, rainy weather in the Mississippi Delta when Maturity Group IV soybeans were in the final stages of maturity (R5-6). Mass yield losses near 100% occurred due to a pod rot from Cercospora kikuchii. Infection was variety specific leaving some fields unaffected. Resistance to infection was evaluated in the laboratory for 277 varieties. For each variety, 20 green R6 field grown pods were surface sterilized in 15% sodium hypochlorite for 3 minutes, and aseptically placed in moist chambers (Hoffman # Cont 156C). Ten pods were sprayed with a 200,000 spore/ml solution of C. kikuchii, and ten with sterile water as a check. The moist chambers were incubated (Percival I-35D) at 85°F for 7 days. Pods were rated by percentage of surface area infected. Resistant (R) soybeans were not infected, moderately resistant (MR) were up to 25% infected, moderately susceptible (MS) were 25% to 75% infected, and susceptible (S) were over 75% infected. Thirty-one varieties were S, 185 were R, and 61 were MR to MS. This method can help producers select Cercospora resistant soybeans.
SCALA brand SC fungicide for the control of diseases of southern crops. L. FOUGHT, J. R. Bloomberg, G. H. Musson, R. Kaiser, and R. Schwehr. Bayer CropScience, Research Triangle Park, NC 27709. Publication no. P-2005-0005-SOA.
SCALA brand SC fungicide is a highly effective new fungicide containing the active ingredient, pyrimethanil, belonging to the relatively new anilinopyrimidine class of chemistry. Pyrimethanil is an amino acid synthesis inhibitor that prevents the secretion of fungal enzymes necessary for the infection process. Southern crop diseases controlled by SCALA include: botrytis gray mold (Botrytis cinerea) in strawberries; brown rot blossom blight (Monilinia fructicola and M. laxa), shot hole (Wilsonomyces carpophilus), and scab (Cladosporium spp.) in stone fruit (except cherries); botrytis leaf spot and neck rot (B. squamosa and B. allii) and purple blotch (Alternaria porri) in onions and other bulb vegetables; early blight (Alternaria solani) and gray mold (Botrytis cinerea) in tomatoes; and early blight (Alternaria solani) in potatoes and other tuberous and corm vegetables. SCALA is rainfast as soon as the spray material dries, and SCALA is an excellent rotation partner for use in resistance management programs. Trial results, pending label directions, and a state registration update will be presented.
Stability of response of advanced peanut breeding lines and Bolivian Bayo Grande to leaf spot and tomato spotted wilt at multiple locations. S. K. GREMILLION (1), A. K. Culbreath (1), J. W. Todd (1), D. W. Gorbet (2), and R. Pitman (3). (1) Univ. of Georgia, Tifton, GA; (2) Agronomy Dept, Univ. of Florida, Marianna, FL; (3) USDA-ARS, Griffin, GA. Publication no. P-2005-0006-SOA.
Research aims were to assess the field resistance levels of advanced peanut breeding lines and a Bolivian cultivar to early and late leaf spot, caused by Cercospora arachidicola and Cercosporidium personatum, respectively, and tomato spotted wilt (TSW), caused by tomato spotted wilt virus, at three locations in Georgia. Three tests were planted in a split plot design with fungicide regimes as the whole plots and genotypes as the split plots. Fungicide regimes included a nonsprayed control and two applications of tebuconazole. The cultivars Georgia Green (GG), Bolivian Bayo Grande (BG), C-99R, MDR-98 and the advanced lines RP-01, RP-08 and RP-14 were compared. When STAUDPCs were measured, genotype was significant at all locations (P = <.0001). Fungicide was significant at one location (P = .0092). TSW occurred at two sites, but was significant at only one (P = .0006). BG and all advanced lines showed lower levels of leaf spot than in Georgia Green and lower levels of TSW at Tifton.
Impact of fungicides on southern rust and southern corn leaf blight in Georgia. R. C. KEMERAIT, JR. (1), W. D. Duffie (2), W. J. Ethredge (3), and L. Lanier (4). (1) Department of Plant Pathology, Tifton, GA 31793, The University of Georgia Cooperative Extension Service; (2) Dawson, GA 39842; (3) Donalsonville, GA 39845; (4) Millen, GA, The University of Georgia. Publication no. P-2005-0007-SOA.
Four field corn trials were conducted in Seminole and Terrell Counties to evaluate management strategies for southern corn leaf blight (Bipolaris maydis) and southern rust (Puccinia polysora). In 2003, DK 687 and Pioneer 31G98 were planted; Pioneer 32W86 was included in Terrell Co. In 2004, Pioneer 32W86 and DK 6760 were planted. Treatments were an untreated check, Stratego (10 fl oz/A) applied when symptoms first appeared, and Quadris (9.0 fl oz/A) 2 weeks later in half of plots treated with Stratego. Disease severity was assessed and yields were collected. Southern corn leaf blight was predominant in 3 of 4 trials. Use of fungicides did not improve yield or reduce disease severity for this disease. Where southern rust was severe, untreated DK 687 (188.6 bu/A) yielded as well as DK 687 with one (187.7 bu/A) or two (187.3 bu/A) fungicide applications. Yields were similar for the 3 cultivars in untreated plots; however 32W86 and 31G98 out-yielded DK 687 when 2 fungicides were applied to each.
Magnaporthe grisea race shift for virulence to the major R gene, Pi-ta, in Arkansas. F. N. LEE (1), R. D. Cartwright (1), Y. Jia (2), and J. C. Correll (1). (1) Plant Pathology, University of Arkansas, Fayetteville, AR 72701, USA; (2) DB NRRC, USDA-ARS-SPA, Stuttgart, AR 72160. Publication no. P-2005-0008-SOA.
In 1989, following severe blast epidemics with ‘Newbonnet’ rice, Arkansas plant breeders released ‘Katy’ rice containing the major R gene, Pi-ta that conferred resistance to U.S. M. grisea races. Although isolates from laboratory tests and race IE-1K are virulent to Pi-ta, only race IE-1K was isolated infrequently from commercial fields and field plots since early 1990’s. Pi-ta based cultivars were widely utilized in U.S. production areas without any known reports of field infection beyond a few random plants. In August, 2004, however, severe blast disease occurred in a seed field of ‘Banks’ rice. Seeding records and DNA analysis of infected plants confirmed the cultivar as Banks containing the Pi-ta gene. Tests with M. grisea isolates from infected ‘Banks’ plants confirmed virulence on Pi-ta cultivars and all exhibited a host range similar to race IE-1K. Preliminary PCR analysis indicate Banks isolates lack a functional AVR-Pita gene as does IE-1K. Further Rep-PCR analysis indicate the DNA profile of Banks isolates differs from known IE-1K isolates.
Role of resistance genes and anatomical changes in flood-mediated rice blast field resistance. F. N. LEE, M. P. Singh, and P. A. Counce. Rice Research and Extension Center, University of Arkansas, 2900 Hwy 130E, Stuttgart, AR 72160, USA. Publication no. P-2005-0009-SOA.
Arkansas growers produced record rice yields in disease conducive years 2000-2004 growing cultivars susceptible to blast caused by Magnaporthe grisea. The primary blast control measure was flood-induced field resistance (FFR) that is mediated by hypoxic soil conditions. Resistance mechanisms and host-pathogen relationships of FFR were investigated utilizing deep flood and/or ethephon treatments. Field resistance was induced in all susceptible cultivars tested. FFR response was small in highly susceptible cultivars such as M-201, intermediate in cultivars with minor resistance genes such as Wells, and approached immunity in cultivars with major R genes such as Drew. Anatomical studies indicated leaf vascular bundles of plants growing upland were poorly organized while those growing under continuous flooded or upland conditions with 50 ppm ethephon were well organized with enlarged cells within the leaf veins. Mycelia growth was restricted between and within major and minor lateral veins of plants exhibiting FFR. Mycelia constraint appears structural and physiological in nature.
Incidence of Phomopsis longicolla and other fungi associated with soybean seed in the early soybean production system plantings in the midsouthern USA. A. MENGISTU and L. G. Heatherly. USDA-ARS, Crop Genetics & Production Research Unit, PO Box 345, Stoneville, MS 38776. Publication no. P-2005-0010-SOA.
Field studies were conducted from 1995 to 1997 and in 2001 at Stoneville, MS to determine the effects of maturity group (MG), year, date of planting (DOP), and irrigation on the incidence of Phomopsis longicolla (PL), the principal causal organism for soybean seed decay. The role of Macrophomina phaseolina (MP) and Fusarium sp. (FS) in the early soybean [Glycine max (L.) Merr.] production system (ESPS) was also investigated. There was a significant effect due to year, irrigation, and MG. Maturity group averaged over years, DOP, and irrigation showed that MG IV seed had a significantly higher PL incidence than did MG V seed. Irrigated treatments in dry years produced a higher level of PL than did nonirrigated treatments. There were high and significant inverse relationship between incidence of seed infected with PL and seed germination (r = –0.87, P < 0.05), and between incidence of seed infected with FS and seed germination (r = –0.65, P < 0.05). This research highlights not only the importance and significance of PL but also the importance of other organisms that in combination may inflict considerable damage to quality of seed harvested from ESPS plantings.
Influence of soil texture on Meloidogyne incognita induced yield suppression of cotton. W. S. MONFORT (1), T. L. Kirkpatrick (2), and A. Mauromoustakos (1). (1) Dept. of Plant Pathology, Univ. of Arkansas, Fayetteville, AR 72701; (2) SWREC, Univ. of Arkansas, Hope, AR 71801. Publication no. P-2005-0011-SOA.
Meloidogyne incognita population densities and influential soil factors were evaluated in 2001 and 2002 in a cotton field in Arkansas to evaluate their effects on yield. The 6-hectare field was subdivided into 512 grid plots (30.5 meters × 3.9 meters) and sampled for M. incognita in April, May, July, and October. Soil texture was also determined from each grid plot. Fumigant nematicide, 1,3-dichloropropene (Telone II) was applied in strips through the field at 14.2, 28.4, and 42.6 liters/ha. to create zones within the field with differential population densities of the nematode. Statistical analyses were conducted in utilizing stepwise and multiple regression. Variables that were important in explaining cotton yield differences were percent sand, nematicide application, and M. incognita (April 2002 density), although only <30% of the variability was accounted for. However, when the individual grid plots were aggregated based on four arbitrarily selected soil textural ranges (0-30% sand, 31-45% sand, 46-60% sand, and >60% sand), and analyzed based on the nematicide treated zones within each textural class, 89% of the yield variability was accounted for in 2002. These findings indicated that soil texture might have a significant impact on damage potential of M. incognita on cotton yield.
ABSOLUTE 500 SC for the control of peanut diseases. G. H. MUSSON, J. R. Bloomberg, L. Fought, R. Kaiser, R. Kraus, and R. Myers. Bayer CropScience, Research Triangle Park, NC 27709. Publication no. P-2005-0012-SOA.
ABSOLUTE 500 SC (tested under the Bayer code USF 2010) is a fungicide in development for use in peanut. ABSOLUTE 500 SC at 3.5 fl oz/A has demonstrated excellent crop safety and control of most major foliar diseases including: early and late leaf spot (Cercospora arachidocola and Cercosporidium personatum), web blotch (Phoma arachidicola), and rust (Puccinia arachidis). Additionally, ABSOLUTE 500 SC can be tank-mixed at select timings with a reduced rate of Folicur 3.6 F to achieve control of white mold (Sclerotium rolfsii) and limb rot (Rhizoctonia solani) and help with resistance management concerns. Trial results from 2004, pending label directions, and a registration update will be presented.
Stripe rust: an emerging problem in Louisiana wheat. G. B. PADGETT (1), B. C. W. Garber (2), and M. A. Purvis (1). (1) Northeast Research Station, LSU AgCenter; (2) Dean Lee Research Station, LSU AgCenter. Publication no. P-2005-0013-SOA.
Stripe rust, Puccinia striiformis, is an emerging disease in Louisiana wheat. Beginning in 2001, this disease has increased in incidence and severity. Epidemics initiate earlier than leaf rust increasing the potential for yield loss. Studies were conducted to evaluate rates and timings of commercially-available fungicides for efficacy against stripe rust. Tilt 3.6EC (4.0 fl oz), Quadris 2.08SC (6.2 fl oz), and Headline 2.08EC (6.2 fl oz) were applied to wheat at flag leaf emergence or heading. Tilt 3.6EC was more active against stripe rust than Quadris or Headline. Early applications were more effective for minimizing disease severity than later applications; however, yield losses were minimized for all application timings. Ambient temperature and relative humidity was monitored during the growing season to determine their impact on epidemics. High relative humidity and cool nighttime temperatures (4 to 15°C) fueled epidemics into April. Research has been initiated to characterize epidemics in an effort to forecast fungicide application timings.
Effect of fungicide seed treatment and seed quality on soybean stand and yield in Arkansas. M. L. ROSSO, J. C. Rupe, C. S. Rothrock, M. T. Kirkpatrick, R. Cartwright, C. Tingle, M. Poop, and S. A. Winters. Dept. Plant Pathology, University of Arkansas, Fayetteville, AR 72701. Publication no. P-2005-0014-SOA.
The efficiency of ten fungicide seed treatments was determined on high and low quality seed lots of the soybean cultivar Pioneer 94M90 at three locations in Arkansas, planted in April, May and June. The treatments included five selective fungicides and five broad-spectrum fungicides (some included insecticides). Significant increases in stand occurred across location and planting dates with the broad-spectrum seed treatments. Metalaxyl (Allegiance) was the least effective seed treatment of the selective fungicides indicating a limited role of Pythium spp. in seedling diseases. Low quality seed reduced stands. However, Stilletto (carboxin-thiram-metalaxyl) significantly improved the stand and yield of low quality seeds. Yields generally reflected stand within a planting date. Yields significantly declined with delays in planting. Seed treatments showed better stand improvement in the May and June than in the April planting dates.
Suppression of pink root and Botrytis neck rot of onion with fungicides. K. W. SEEBOLD and D. B. Langston. Plant Pathology Dept., University of Georgia, CPES, Tifton, GA 31793. Publication no. P-2005-0015-SOA.
Pink root (PR), caused by Phoma terrestris and Botrytis neck rot (BNR), caused by B. allii, are the most damaging soilborne diseases of sweet onion in Georgia. Pink root occurs on onion roots prior to harvest of bulbs, while losses associated with BNR may occur prior to harvest or during cold storage. To evaluate the potential for suppression of PR and BNR with fungicides used in onion disease control programs, field trials were conducted at two locations in 2003 and 2004. Results from 2003 indicated that a pre-mix of boscalid and pyraclostrobin (BP) applied full-season at 16 oz/A significantly reduced (P < 0.05) the severity of PR on mature bulbs, while BNR on onions cold-stored 5 months was reduced by more than 4 times compared to the untreated control. In one location in 2004, significant suppression of BNR was achieved with as few as two applications of BP made early- and mid-season as part of a spray program. Levels of PR were also reduced. The use of BP in spray programs aimed at management of foliar diseases of onion appears to be of value in managing soilborne pathogens as well.
Molecular identification of Uncinuliella australiana as the powdery mildew pathogen of crape myrtle (Lagerstroemia indica). A. SHI, M. T. Mmbaga, and S. Zhou. Tennessee Sate University, Otis A. Floyd Nursery Research Center, 472 Cadillac Lane, McMinnville, TN 37110. Publication no. P-2005-0016-SOA.
Teliomorphs are often used to identify powdery mildew fungi; however they rarely develop on crape myrtle. To identify the causal agent of powdery mildew of crape myrtle (Lagestroemia indica), analysis of the Internal Transcribed Spacer (ITS) region of rDNA was used. Polymorphic bands of 666bp amplified from the primer pair ITS(1)/ITS(4) and 704bp amplified from the primer pair ITS(1)-F/ITS(4) showed a sequence identical to that of Uncinuliella australiana. All 16 isolates of the powdery mildew pathogen collected from different locations in middle Tennessee were identical as U. australiana. Uncinuliella australiana was previously reported to occur in Japan, China and Australia and Erysiphe lagestroemiae was the powdery mildew pathogen reported to occur on crape myrtle in the USA. Our study showed that the powdery mildew in crape myrtle in middle Tennessee was caused by U. australiana and not E. lagestroemina. Four ITS-specific primers were designed and tested to provide a diagnostic tool for the anamorphic powdery mildew of crape myrtle.
Using modeled weather data for predicting Sclerotinia blight of peanut. D. L. SMITH and B. B. Shew. Dept. of Plant Pathology, NC State Univ., Raleigh, NC 27695. Publication no. P-2005-0017-SOA.
In North Carolina, current advisories for Sclerotinia blight of peanut use temperature, rainfall, and relative humidity thresholds measured on site after canopy closure. Systems that use modeled site-specific weather data without on-site sensors have proven useful in disease prediction models for other pathosystems. A similar system may prove useful for implementing Sclerotinia blight advisories. Cultivars with a spectrum of resistance levels and three rates of fungicide were used to establish varying levels of disease over multiple years and sites. Weekly incremental disease incidence (IDI) was recorded in all plots. Weather data were collected at several sites and modeled for all sites by SkyBit Inc. Five-day moving averages were calculated from the weather data. IDI was the dependent variable in analyses describing effects of the parameters on disease development. Results of principal components analyses were used to select parameters to input in a stepwise regression analysis with IDI as the dependent variable. Nonlinear and interaction effects of the selected parameters were evaluated. A model predicting IDI was devised and will undergo evaluation in 2005.
Impact of foliar fungicides on soybean yield and net returns. B. L. SPINKS (1), D. H. Poston (2), G. L. Sciumbato (2), and M. A. Blaine (1). (1) Plant and Soil Sci. Dept., Mississippi State Univ., Mississippi State, MS 39762; (2) Delta Res. and Ext. Center, Mississippi State Univ., Stoneville, MS 38776. Publication no. P-2005-0018-SOA.
Twelve foliar fungicide treatments were evaluated at R3-4 and R5-6 growth stages in Mississippi in 2003 (5 locations) and 2004 (4 locations). Treatments were: 1) 6.2 oz/A Quadris, 2) 0.75 lb/A Topsin M, 3) 1.5 pt/A Bravo Weatherstik, 4) 2 oz/A Dimilin, 5) 6.2 oz/A Quadris + 0.5 lb/A Topsin M), 6) 6.2 oz/A Quadris + 1.0 pt/A Bravo Weatherstik, 7) 6.2 oz/A Quadris + 2 oz/A Dimilin, 8) 1.25 lb/A Solubor + 2 oz/A Dimilin, 9) 3.1 oz/A Quadris + 2 oz/A Dimilin, 10) 3.1 oz/A Quadris + 0.5 lb/A Topsin M, 11) 5 oz/A Tilt, 12) 3.9 oz/A Tilt + 4.1 oz/A Quadris, and a 13) Nontreated control. Averaged across all locations and timings, Quadris at 6.2 oz/A applied alone or in combination with other products increased soybean yield 4.4 to 5.5 bu/A. Similar yield increases occurred with 3.1 oz/A Quadris + 0.5 lb/A Topsin M. Soybean yields with these treatments averaged 2.4 bu/A higher with R3-4 applications than with R5-6 applications. Quadris at 6.2 oz/A and Quadris at 6.2 oz/A + 2 oz/A Dimilin were the most profitable treatments and increased net returns $11.55 and $14.54/A, respectively compared to the untreated control.
Occurrence of fusiform rust in plantings of previously inoculated gall-free pine seedlings. C. H. WALKINSHAW. USDA Forest Service, Pineville, LA. Publication no. P-2005-0019-SOA.
Fusiform rust inoculated, but symptom-free seedlings of loblolly (Pinus taeda L.) and slash (P. elliottii Engelm. var. elliottii) pines can develop stem galls when planted in the field. As many as 55% of the outplanted loblolly and 54% of the slash pines formed stem galls within one meter of the soil within a 3 year period. The progeny of known highly resistant families of both pine species generally did not form galls in the field. The overall means for all seedlings with galls in this study was 20% for loblolly and 19% for slash pines. Typical gall formation in susceptible seedlings was the same in the greenhouse and the field plantings. Galls developed in newly emergent shoots, which were examined by light microscopy. Histological examination of infected tissues from field and greenhouse proved similar to our earlier findings of resistant and susceptible reactions. These results raise questions about planting seedlings labeled gall-free.
First occurrence of Sclerotinia blight on peanut in Georgia. J. E. WOODWARD (1), T. B. Brenneman (1), R. C. Kemerait (1), and J. R. Clark (2). (1) Department of Plant Pathology, University of Georgia, Tifton, GA 31793; (2) University of Georgia Cooperative Extension Service, Baxley, GA 31535. Publication no. P-2005-0020-SOA.
Sclerotinia sclerotiorum is a serious pathogen of several winter crops in Georgia, but it has not previously been reported on peanut (Arachis hypogaea) in the state. The pathogen has only rarely been found on peanut in the United States, even in areas where S. minor causes major losses. Previous attempts at field inoculations with S. sclerotiorum in Georgia have been unsuccessful. In 2004, signs and symptoms typical of Sclerotinia blight were observed in Appling County in a field never previously having a peanut crop. Symptoms were most evident on cultivars C34-24, AP-3, and GA-02C, with almost no disease observed on Georgia Green, the current commercial standard. Isolation of the fungus on potato dextrose agar confirmed identity of the pathogen. Work is underway to determine the relative susceptibility of peanut cultivars and to further classify isolates of S. sclerotiorum from peanut.