Effects of registered pesticides on growth and zearalenone production by fusarium roseum

Zearalenone is one of several mycotoxins produced by Fusarium roseum. It has been implicated as the causative agent of a condition known as hyperestrogenism in swine which causes swine to develop genital tract abnormalities. The fungus is one of the major pests to corn resulting in contamination both in the field and in storage. Pesticides are used on corn to control fungal and insect pests. This study was undertaken to determine if some of these pesticides registered for use on corn have any inhibitory effects on the growth or zearalenone production by Fusarium roseum. The pesticides tested were Bux®, carbaryl, carbofuran, EPN, naled, Dasanit®, Dyfonate®, Toxaphene®, heptachlor, and Dithane M-45®. Growth inhibition studies were carried out by inoculating flasks containing potato dextrose broth with the fungus and adding 0, 10, 50, and 100 ppm of each pesticide. The cultures were allowed to grow for three weeks at 21° C after which the mycelial mats were dried and weighed. The dried weight was used as an indication of growth. All pesticides, except for carbofuran, were found to inhibit growth by the following percentages: Bux®, 70%; naled, 100%; Dasanit®, 56%; Dyfonate® , 33%, carbaryl, 71%; Toxaphene®, 42%; heptachlor, 49%; EPN, 35%; and Dithane M-45®, 100%. Flasks containing 50 g. of corn were inoculated with the same pesticides, excluding heptachlor and Toxaphene®, to give final concentrations of 0, 10, 50, and 100 ppm. The cultures were allowed to remain at 21° C for one week and then at 15° C for three weeks. The samples were extracted with benzene, chloroform, sodium hydroxide, and citric acid. Quantitation was done by HPLC analysis using the fluoresence detector and a μ-Porasil column. It was found that three of the pesticides inhibited zearalenone production by greater than 90%. The percentages of zearalenone inhibition were as follows: naled, 100%; Dasanit®, 90%; carbofuran, 97%. EPN, carbaryl, Bux®, Dyfonate®, and Dithane M-45® did not significantly inhibit zearalenone production.