Incompatibilities Between Herbicides and Insecticides in Direct-Seeded Brassica Crops1

Abstract

The compatibility of 5 preemergence herbicides and 3 insecticides applied in silt loam was assessed in 4 brassica crops by comparing their effects on germination, plant stand, and yield. Several combinations were deleterious. The herbicides CDEC and DCPA in combination with the insecticide thionazin reduced plant stand in cabbage and cauliflower. Herbicide C-7019 in combination with the insecticide fensulfothion was incompatible for cabbage and broccoli. Cabbage germination was reduced; while with broccoli both the germination and crop yield were affected. C-7019 alone reduced the germination of cauliflower and in combination with fensulfothion the damage was increased. This herbicide was phytotoxic to rutabaga. When nitrofen was combined with the insecticides, plant stands of cauliflower and rutabaga were affected. Nitrofen and thionazin together reduced the plant stand of cabbage. Propachlor at 4 lb./acre was compatible with any of the three insecticides for the four crops. However, the plant stand and yields of all four crops were reduced in plots treated with propachlor at 6 lb./acre in combination with thionazin. Propachlor with the insecticide carbofuran injured only broccoli. The herbicides did not affect the efficacy of the insecticides.