The Influence of Several Crop Sequences on the Incidence of Verticillium Wilt of Cotton and on the Population of Verticillium dahliae in Field Soil

Abstract

Since V. dahliae was not detectable by soil assay or by subsequent infection of cotton [Gossypium hirsutum] plants, it was considered to be eradicated from most field test plots following a 1 yr rotation between cotton and paddy rice [Oryza sativa], (continuous flooding). In contrast, populations of V. dahliae per gram of soil were increased with rotations to safflower [Carthamus tinctorius] or with continuous cotton. Keeping soil wet but not flooded for 6 wk and/or rotations with grain sorghum [Sorghum bicolor], or dry fallow did not change the concentration of V. dahliae propagules in soil. Significant (P = 0.05) decreases in disease incidence and increases in cotton lint yields resulted from rotations with paddy rice perennial ryegrass [Lolium perenne], and in some fields from safflower, grain sorghum, or frequent soil irrigation followed by grain sorghum.