Assessment of the effects of intercropping patterns on incidence and damage to cotton by Diaparopsis castanea Hampson (Lepidoptera: Noctuidae) in Magoye, Mazabuka District of Zambia

The Red bollworm, Diaparopsis castanea (Hampson) is an insect that has gone from being a minor cotton pest to being a major pest of cotton in Zambia. This study was conducted in Magoye, Mazabuka district, Southern province of Zambia. The main aim of the study was to assess the effects of intercropping patterns on the incidence and damage caused to cotton by D. castanea. The study was conducted in two parts during the 2010/11 farming season.

Part A involved conducting a survey among 80 randomly selected farmers in Magoye to determine the different types of intercropping patterns , if any at all, being used in the area. Part B was an experimental field study to assess various intercropping patterns identified from the survey. The experiment was laid out in a randomized block design with four replications. Cotton cultivar CDT II (Gossypium hirsutum spp) was sown by hand in 100-cm spaced single rows. The intercrops selected were Maize (Zea mays L.), Sorghum (Sorghum vulgares L.) Pigeon pea (Cajanus cajan L.), Cowpea (Vigna unguuiculata L.) and Sunflower (Helianthus annus L.). The data collected was subjected to analysis of variance (ANOVA) technique and LSD using GenStat discovery edition 3 computer package.

The survey revealed that only 28% of farmers in Magoye area were using intercropping as a pest control strategy. The intercrops were grown either as a strip/single row pattern alongside the cotton crop or in between each row of cotton. Analysis of variance (ANOVA) on the field study showed significant differences (F =2.22; d.f =5; P<0.001) in incidence of D. castanea egg, average damage to cotton bolls (F = 1.25; d.f = 5; P<0.001) and average seed cotton yield (F =1.17; d.f = 1.17; P<0.001) across the various intercropping patterns.

Results of the present study confirm that intercropping is being used by farmers in Magoye, Mazabuka district of Zambia. The Experiment further showed that none of the intercrops selected were alternative hosts for D. castanea. Based on overall seed cotton yield, cotton-sunflower treatment was the most effective intercropping pattern as it produced the highest  yield of 303kg/ha.