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At two locations, propiconazole (Tilt)® was applied to Florunner groundnuts (Arachis hypogaea L.) in volumes of water ranging from 187 to 561 l ha−1 in ground sprays and from 2·3 to 6·4 mm in chemigation applications. A total of 4296 fungal isolates were cultured from groundnut shells obtained from the two sites located near Tifton, Georgia, U.S.A. Nearly two-thirds of the isolates were members of the Fungi Imperfecti. The most frequently observed species were from the form-genera Alternaria, Botryodiplodia, Curvularia, Epicoccum, Fusarium, Nigrospora, Phoma, Rhizoctonia and Trichoderma. The pesticide applications showed few effects on isolation frequency at either test site. Malt extract, potato dextrose and tannic acid-benomyl agar were used for initial isolations. Isolation frequencies of the nine most common genera were significantly different on these cultural media for only Botryodiplodia and Nigrospora.

Stands from atesta (bald) seed 10 and 20 days after planting were 32.0 and 35.5% less than stands from intact seed in field plots. Thirty-two and 62 days after planting the fresh weights of plants from bald seed were 32.3 and 15.3% less than those from intact seed. Pod yield of plants from bald seed was 20.4% less than that from intact seed. Sound mature kernels (SMK) produced by plants from bald seed was 1.2% less than the SMK from intact seed. When plant populations in field plots were adjusted by covariance analysis to equal numbers, no difference in yield was predicted. Plants grown from bald and intact seed in field microplots fumigated with metam-sodium had no difference in yield or SMK. Bald seed germinated in 24 hr cycles of 20 C/16 hr + 30 C/8 hr had fewer normal rapid and more normal slow germinating seedlings than intact seed. At temperatures of 30 C/16 hr + 20 C/8 hr, there was no difference in germination percentages. In soil infested with Aspergillus niger van Tieghem at 21 C/12 hr + 27 C/12 hr there was no difference in seedling emergence from bald or intact seed after 22 days. At temperatures of 15 C/12 hr + 21 C/12 hr, seedling emergence from bald seed in A. niger infested and noninfested soil was less than that of intact seed in control soil. Emergence of seedlings from bald seed was zero and that from intact seed was less than other treatments at both temperature regimes in soil infested with Rhizoctonia solani Kühn anastomosis group 4.

Cylindrocladium black rot (CBR), a devastating disease of peanut (Arachis hypogaea L.), is caused by Cylindrocladium crotalariae (Loos) Bell and Sobers [perfect state, Calonectria crotalariae (Loos) Bell and Sobers]. No effective chemical control is known. Resistant cultivars would be the best way to control the disease. Two screening methods, employing sterile and nonsterile media, were developed and used for large-scale systematic screening of peanut genotypes for resistance. Results were reproducible with either method. The nonsterile method was more economical, required less handling, and permitted immediate transplanting of selections. Using both methods, we evaluated 929 different peanut lines from the world germplasm pool. Some 130 lines (14%) exhibited sufficient resistance to be reevaluated. After repeated screening by single-plant selection, six derived inbreds with greater resistance than the standard resistant Span-cross and NC 3033 peanuts were named CBR-R1 to CBR-R6 and released as germplasm lines for breeding use. They include representatives from three of the four botanical varieties of A. hypogaea.

Peanut, corn and soybean seed were inoculated with 14 isolates of Aspergillus flavus Link and A. parasiticus Speare. The seeds were hand sorted to remove all visibly damaged seeds and were fumigated under vacuum (-95.25 k Pa Hg) with 2.2% cyano (methylmercuri) guanidine at 37 C for 48–96 hours. All fumigated seed had a minimum of 95% germination and a maximum of 5% residual contamination by fungi and bacteria. Corn and peanut samples (100 g/flask) were rehydrated to 28% moisture and inoculated with all isolates; soybean samples (100 g/flask) were rehydrated to 28% moisture and inoculated with four A. flavus and two A. parasiticus isolates. Samples were incubated for 10 days at 30 C and analyzed for aflatoxins. Aspergillus parasiticus isolates produced aflatoxin B1, B2, G1 and G2 while A. flavus isolates produced aflatoxin B1 and B2. Mean B1 production for 12 isolates was 34 mg/kg in peanut seed and 3.6 mg/kg in corn seed. Two A. flavus isolates produced 3.8 to 5.4 mg/kg B1 in peanut seed, and 2.2 mg/kg in corn seed. Overall, the mean B1 production was about 10 times higher on peanut seed than on corn seed. However, more G1 was produced on soybean seed than B1. The isolate and the substrate are apparent limiting factors in aflatoxin production. Peanut seed accumulated more aflatoxin than corn or soybean seed when inoculated with the same isolates and incubated under similar conditions.

Yellow nutsedge (Cyperus esculentus L.) is a serious weed problem in the United States and other countries. An indigenous rust fungus [Puccinia canaliculata (Schw.) Lagerh.], pathogenic on yellow nutsedge, was released in early spring as a potential biological control agent. The fungus inhibited nutsedge flowering and new tuber formation. The fungus also dehydrated and killed nutsedge plants. The successful control of yellow nutsedge by a rust epiphytotic under experimental conditions demonstrates the potential use of the rust in an integrated weed management system.