THE EFFECT OF TCA ON GREEN FOXTAIL IN COMPETITION WITH CEREALS

Abstract

In 1960, 1961 and 1962 the sodium salt of trichloroacetic acid was applied at rates up to 8 pounds per acre to seeded infestations of green foxtail (Setaria viridis (L.) Beauv.) in crops of Rodney oats, Parkland barley and Selkirk wheat. Treatments were applied when the crop plants had 3 or 4 leaves and the weeds 1 or 2 leaves. Oats and barley yields were not affected by any rate of TCA used. Wheat yields were reduced by all rates of TCA above 2 pounds per acre. The numbers of foxtail plants in the oats were not greatly reduced by any of the TCA treatments but 6 pounds per acre in wheat and 3 pounds per acre in barley killed 50 per cent or more of the plants. Foxtail growth was suppressed by all treatments; the degree of suppression increased with increasing rates. This suppression failed to result in increased crop yields because of the low level of the foxtail infestations. TCA at 3 pounds per acre prevented seed production of foxtail in wheat and oats, but only 1 pound per acre was needed to accomplish this in the more competitive barley crop. The effectiveness of the TCA treatments was influenced by the competitive ability of the cereal crop, being greatest with barley and least with wheat. The prevention of seed formation with TCA has an important practical application in the eventual elimination of foxtail seeds in the soil.