COMMON ROOTROT AND PLANT DEVELOPMENT FOLLOWING TREATMENTS OF WHEAT SEED WITH ALDRIN, GAMMA BHC, AND HEPTACHLOR, WITH AND WITHOUT MERCURY FUNGICIDES

Abstract

Common rootrot in Chinook wheat seedlings was more pronounced after seed treatments with gamma BHC at 1 oz. per bu. than after aldrin or heptachlor at the same rate or no insecticide, in soils inoculated with Cochliobolus sativus (Ito and Kurib.) Drechs. ex Dastur in greenhouse and field tests. In one of four tests rootrot was greater after heptachlor than after aldrin seed treatments. Disease increased progressively with an increase in rate of application of gamma BHC, but not of heptachlor, from [Formula: see text] to 1 oz. per bu. Reduced emergence and seedling weight following the higher rates of gamma BHC apparently were caused by phytotoxicity of the seed dressings rather than by the increases in rootrot. In field tests rootrot frequently was greater, and emergence less, without insecticides than with most insecticides, possibly because of damage to the plants by wireworms.The inclusion of a mercury fungicide with the insecticide, except gamma BHC at [Formula: see text] and 1 oz. per bu., usually reduced rootrot and increased emergence and seedling weight in inoculated soils.Wheat plants apparently recovered from early stunting associated with phytotoxicity and rootrot as there were no differences in grain yield per plant between seed treatments or between inoculated and uninoculated soils.