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Ken Obasa, Jack Fry, and Megan Kennelly

patch, caused by Rhizoctonia solani AG 2-2 LP, is the most common and severe disease of zoysiagrass in the transition zone and everywhere zoysiagrass is used. It can cause large areas of blighted turf in the spring and fall. Typical symptoms appear as

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Arlette S. Cuomo, Steven E. Newman, Hassan H. Nassar, and Ronald J. Harkrader

There are many naturally occurring substances that have the potential to be adapted to modern pest control chemistry. Azadirachtin, an insect growth regulator, is one such naturally occurring compound that has been widely accepted in insect pest management. Quartenary benzophenanthridine alkaloids (QBAs) are known to be effective in the control of crop-damaging fungal diseases. QBAs can be isolated from plants in the Papaveraceae. Extracts of Macleaya cordata, a species rich in QBAs, were formulated for drench application to Cucumis sativa `White Wonder' seedlings. The seedlings were grown in a peat-lite medium using 10-cm plastic pots and inoculated with Rhizoctonia solani. Test formulations were prepared with and without QBAs and applied at 75, 150, and 300 ppm QBAs as a 100 ml/pot drench. The QBA formulations that provided effective control of Rhizoctonia solani lost 20% or fewer seedlings compared to the formulation without QBA, which lost more than 60% of the seedlings. Treated plants were evaluated confirming Rhizoctonia solani infection.

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Dipak Sharma-Poudyal, Timothy C. Paulitz, and Lindsey J. du Toit

Rhizoctonia solani causes stunting of onion ( Allium cepa L.) in the coarse, sandy soils of the semiarid Columbia Basin of Oregon and Washington States ( Patzek et al., 2013 ). The disease occurs in the cereal-onion cropping systems of this region

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Kimberly A. Cochran and Craig S. Rothrock

manure crop and rate of application on plant growth, disease symptoms, and Rhizoctonia solani isolation frequency from impatiens. z Table 2. Effects of brassica green manure crop and rate of application on plant growth, disease symptoms, and

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J. A. Thies, P. A. Berland, and R. L. Fery

Rhizoctonia solani is an important pathogen of cowpea (Vigna unguiculata) in the southern U.S. and worldwide. Cowpeas are especially susceptible to seedling diseases caused by R. solani when planted in cold, moist, spring soils. Nine cowpea cultivars were evaluated in inoculated field tests at six planting dates in Charleston, S.C., during 2004. The cowpea cultivars evaluated were Bettergro Blackeye, Knuckle Purple Hull, Mississippi Silver, Colossus-80, Charleston Nemagreen, Texas Cream-40, White Acre, Coronet, and Charleston Greenpack. The tests were planted on 20 Apr., 29 Apr., 11 May, 19 May, 27 May, and 8 June. The experimental design for each test was a split-plot with six replicates. Whole plots were cultivars, and sub-plots were inoculation with R. solani and an uninoculated control. Rhizoctonia solani caused significant seedling losses in all cultivars evaluated during mid-April to early June and seed yields were reduced in the 11 May planting. In general, standard cowpea cultivars (Mississippi Silver, Colossus-80, and Coronet) had higher stand counts and produced heavier seed yields than other cowpea cultivars, although these standard cultivars were not resistant to R. solani. Resistant cowpea cultivars are needed to allow earlier planting of the crop in cold soils, which would extend the growing season and allow more efficient use of harvesting equipment and processing facilities.

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Katharina S. Wigg and Irwin L. Goldman

table beet quality and yield is Rhizoctonia root and crown rot caused by the fungus Rhizoctonia solani Kühn (Abawi et al., 1986; Natti, 1953 ; Pethybridge et al., 2018 ), which renders table beet roots unmarketable. Currently, there are few chemical

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Greta Schuster, Roland E. Roberts, and David Bender

Rhizoctonia solani infection of potato causes seed piece decay and stem and tuber lesions, resulting in delayed emergence and uneven stands, low-vigor plants and unmarketable tubers. Rhizoctonia prevention effectiveness of three fungicide/fir bark dusts and nontreated tubers were compared on three varieties. Seedpieces of Viking, Atlantic and Norkotah 278 were treated and planted in separate commercial fields. A randomized complete-block design with four replications with four 26-foot rows per treatment plot included four treatments: 0.5 lb Maxim, 1.0 lb Tops MZ, and 1.5 lb Nubark Captan dust/100 lb seed. Plant stems, stolons and tubers were examined for Rhizoctonia infection at the tuber initiation stage and tubers were examined again at mature stage. Maxim and Tops MZ reduced stolon infection in Atlantic and Norkotah 278 and reduced stem infection in Norkotah 278. Plants from Maxim treated tubers produced more stems/plant in Norkotah 278 and produced more weight of tubers weighing less than four oz in all three varieties. Differences in seed tuber conditioning and mechanical damage in seed handling increase variability of treatment effects. Repeated testing of potato seed piece treatments in Texas High Plains conditions is the best way to confirm potential of beneficial effects of seed treatment.

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J. A. Thies, P. A. Berland, and R. L. Fery

Rhizoctonia solani is an important pathogen of cowpea (Vigna unguiculata) in the southern U.S. and is the primary cause of seedling diseases in this crop. Stand losses caused by R. solani are especially severe when cowpea is planted in cold, spring soils. Three cowpea cultivars (Coronet, Knuckle Purple Hull, and Mississippi Silver) were evaluated in R. solani-inoculated field tests at four planting dates in Charleston, SC during 2005. The tests were planted on 25 Apr., 9 May, 27 May, and 13 June. The experimental design for each test was a split-plot with six replicates. Whole plots were cultivars, and sub-plots were inoculated with R. solani and an uninoculated control. Rhizoctonia solani caused significant seedling losses in all cultivars planted on the first three planting dates. Seed weight and seed numbers were reduced for `Mississippi Silver' in inoculated plots for all planting dates. In general, `Mississippi Silver' and `Coronet' had higher stand counts and heavier seed yields than `Knuckle Purple Hull', but all three cultivars were susceptible to R. solani. The development of resistant cowpea cultivars would reduce stand losses due to R. solani and improve seed yields of cowpea planted in cold, spring soils.

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Mei Zhang and Peter H. Dernoeden

Determining anastomosis groups (AGs) of Rhizoctonia solani Kühn isolates is tedious and time-consuming. Three previously described methods (i.e., cellophane strip, glass slide, petri dish) were compared to determine which was the most rapid and accurate. Colony characteristics also were assessed to tentatively identify AGs. All techniques were accurate. The cellophane strip method was most time-consuming, and the time required for hyphal overlap with the glass slide method was not generally predictable. Pairing isolates in a petri dish containing a thin layer of water agar was reliable and was the simplest technique. There was little variation in colony pigmentation or sclerotia color, shape, or formation patterns within AG-1 IA (n = 34), AG-2-2 IIIB (n = 46), and AG-4 (n = 5); the former two AGs are the ones most commonly isolated from cool-season turfgrasses. Accordingly, R. solani isolates from turfgrasses may be assigned tentatively to an AG based on colony pigmentation and sclerotial characteristics.

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Rejah Muhyi and Paul W. Bosland

A reliable screening method to detect Rhizoctonia solani Kuhn resistance in chiles (Capsicum annuum L.) was developed using infested corn (Zea mays Bonaf.) kernels as inoculum. The most aggressive New Mexican isolate of R. solani (PWB-25) was used to screen 74 Capsicum accessions for resistance to root rot caused by the fungus. The accessions differed in resistance, with disease ratings ranging from 2.9 to 8.6 on a 0 (no disease) to 9 (seedling dead) scale. The percentage of resistant plants, those in the interaction phenotype index class 0, 1, 2, and 3, ranged from 2.4% to 77.1%. Nineteen accessions representing four species had ≥50% resistant individuals and would be useful in breeding programs.