Variety and planting date effects on the incidence of bollworms and insect sucking pests of cotton (Gossypium hirsutum L.)

Abstract

Cotton is a major foreign currency earner in Zimbabwe. It is attacked by many insect pests which limit its productivity. A trial carried out at the Cotton Research Institute investigated the effects of planting date and cotton variety on the incidence of bollworms and insect sucking pests of cotton. Three varieties SZ 9314, CRI MS1 and CRI MS2 were planted on three different dates (20 October, 17 November and 15 December), representing early, mid-season and late planting times. Scouting for pests commenced from the fifth week after emergence to 10% boll split. Both planting date (p = 0.027) and cotton variety (p = 0.012) had significant effects on pest incidence. Early planted cotton had lower aphids, jassids and red bollworm population than later-planted cotton. This was due to the higher natural enemies’ population and the effects of the “closed season” in the early crop. CRI MS2 hosted significantly lower populations of aphids, jassids and red bollworms compared to the other varieties. There was interaction between planting date and variety, with early-planted CRI MS2 hosting the lowest populations of aphids and red bollworms. The study concluded that early planting resulted in lower incidence of insect sucking pests and recommended the early planting of CRI MS2.