Effects of Diniconazole on Aspergillus Populations and Aflatoxin Formation in Peanut Under Irrigated and Nonirrigated Conditions. T. B. Brenneman, Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton, GA 31793. D. M. Wilson, and R. W. Beaver. Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton, GA 31793. Plant Dis. 77:608-612. Accepted for publication 11 February 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0608.

Florunner peanuts (Arachis hypogaea) planted in irrigated and nonirrigated plots were either not treated or sprayed four times with diniconazole at 0.07, 0.14, and 0.28 kg/ha in 1988 and 1989. Paired plots in the nontreated and 0.28 kg/ha treatments were infested with a conidial suspension of Aspergillus parasiticus (a member of the Aspergillus flavus group) or left noninfested. Populations of the A. flavus group and the Aspergillus niger group were monitored in the soil throughout the season as well as in the shells and seed after harvest. Treatment with diniconazole had no effect (P ? 0.05) on populations of the A. flavus group in the soil or shells, and reduced populations in seed only in 1989. The fungicide had no effect on soil populations of A. niger but reduced isolation frequencies from both shells and seed. Artificial infestation with A. parasiticus significantly increased A. flavus-group soil populations but had little effect on isolation frequencies from shells or seeds. Irrigation decreased isolation frequencies of both A. flavus and A. niger from shells and seed, but irrigation had no effect on soil populations of A. niger and variable effects on A. flavus populations. Aflatoxins were detected only in 1989. Mean concentrations were 11 and 2 ppb for the nonirrigated and irrigated plots, respectively. Neither fungicide treatment nor infestation with A. parasiticus affected aflatoxin levels. Aflatoxin concentrations were significantly correlated (P = 0.0001) with A. flavus-group populations in both shells and seed (r = 0.70 and 0.57, respectively).

Keyword(s): mycotoxins.