Interactions of agrochemicals applied to peanut; part 2: Effects on fungicides

Field and laboratory experiments were conducted during 2008 and 2009 to study biological and physicochemical compatibility when fungicides were applied in combination with herbicides, insecticides, and micronutrients for the control of leaf spot disease and Sclerotinia blight. In both years, the program with three fungicide sprays was more effective in preventing canopy defoliation caused by early and late leaf spot disease than single fungicide spray irrespective of agrochemical combinations. Although several interactions were noted among agrochemical combinations, most combinations did not affect fungicide efficacy against canopy defoliation or Sclerotinia blight. In some instances, fungicide combinations protected peanut more effectively from canopy defoliation or Sclerotinia blight than standard fungicide treatment. Regardless of the other agrochemicals applied, boscalid was more effective than fluazinam in controlling Sclerotinia blight. Boscalid, boron, clethodim plus crop oil concentrate, chlorothalonil plus tebuconazole, manganese, and 2,4-DB had large effects on solution pH, whereas fluazinam, lambda-cyhalothrin, and pyraclostrobin had little effect on solution pH. Precipitates formed with all fungicide combinations and in most cases permanent precipitates were formed.

► We defined interactions of agrochemicals with respect to disease control.
► We defined changes in solution pH and formation of precipitates with mixtures.
► Magnitude of interactions was relatively minor compared with fungicide alone.
► Changes in solution pH and formation of precipitates varied by combination.