Effects of intercropping systems on incidence and damage to cotton by diaparopsis castenea hampson(lepidoptera:Arctiidae)in Magoye,Mazabuka district of Zambia.

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Chijikwa, Mutibo
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The Red bollworm, Diaparopsis Castenea Hampson, is an insect that has become a major pest of cotton in Zambia. This study was conducted in Magoye, Mazabuka district, Southern province of Zambia. The main objective of the study was to determine the effects of different types of intercropping patterns occurring among cotton farmers in Magoye area and their effects on the incidence and extent of damage caused to cotton by Diaparopsis Castenea. The study was conducted in two parts during the 2010/11 farming season. The first part involved conducting a survey among 80 randomly selected farmers in Magoye during the months of September and October 2010. This was to determine the different types of intercropping systems being used in the study area. Participatory rural appraisal (PRA) techniques, using questionnaires, interviews, focus group discussions (FGD), and transect walks were used to identify the various intercropping systems. The second part was an experimental field study to assess the relationships of the various intercropping systems, pest incidence and severity. The field trial was conducted at Cotton Development Trust (CDT) in Magoye, Zambia. It was laid out in a randomized complete block design (RCBD) with four replications. The six intercropping systems were randomized in main plots. Plot sizes were 4.8 m x 9 m with intercrops planted in between each row of cotton. Cotton cultivar CDT II (Gossypium hirsutum sp) was sown by hand in 100 cm spaced single rows on 1st November 2010. Maize (Zea mays L.), and Sorghum (Sorghum vulgares L.) were sown two weeks after cotton planting. Pigeon pea (Cajanus cajan L.) and Cowpea (Vigna unguuiculata L.) were planted three weeks after cotton sowing and Sunflower (Helianthus annus L.) was planted five weeks after cotton sowing. Observations on incidence of Diaparopsis Castenea, incidences of natural enemies, damage caused by Diaparopsis Castenea, average boll weight, plant height and seed cotton yield were recorded. The data collected were subjected to analysis of variance (ANOVA) and means were compared using Bonferroni’s test. The survey revealed that farmers in Magoye area were using both chemical and cultural practices to control pests in their cotton fields. The chemicals used were mainly synthetic in nature as none of the farmers were recorded to be using naturally made pesticides. The survey further showed that all farmers interviewed were combining chemical control with various cultural practices such as crop rotation or intercropping. Only 28% of the farmers interviewed 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. Cowpeas and beans were the most common combination (22%) of intercrops used, while maize was only used by one percent of the farmers. Analysis of variance (ANOVA) on the field trial showed significant reduction in incidence of Diaparopsis Castenea eggs (P<0.001), damage to cotton bolls (P<0.001) and seed cotton yield (P<0.001) in the intercropping patterns. Cotton- sunflower treatment recorded the highest yield of 303±59.1 kg/ha while cotton – maize treatment had the lowest yield of 169±25.60 kg/ha. The Experiment showed that even though none of the intercrops selected were alternative hosts for Diaparopsis Castenea, cotton – sorghum treatment was able to attract the widest range of predators. Among all the intercropping patterns, cotton – sunflower was the most effective intercrop as it produced the highest overall yields. It is recommended that the study be conducted for two more seasons in order to re-confirm the observations made in the study.
Cotton --Diseases and pests