Studies on potential of companion crops in managing the diamondback moth, Plutella xylostella (L.) (Lepidoptera: plutellidae) in cabbage/kale cropping systems in Kenya

Date of Award

2003

Document Type

Thesis

Abstract

The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae) is a major pest and threat to brassica production in many parts of Africa. The adverse ecological and environmental effects as well as the cost of chemical pesticides that are commonly used in its control, besides the increasing resistance to chemicals makes it necessary to explore alternative control methods. Integrated Pest Management (IPM), being the emerging pest control paradigm, offers a number of options out of which biocontrol, companion cropping among others, have great potentials. This study investigated the potential of utilising companion vegetable crops as trap or repellent crops in managing the diamondback moth in cabbage/kale cropping systems. Crop preferences for oviposition and suitability for survival and development of P. xylostella were assessed in the laboratory on seven different test plants: cabbage (Brassica oleracea var capitata L.), kale (Brassica oleracea var. acephala L.), rape seed (Brassica napus L. subvar. oleifera), Ethiopian mustard (Brassica carinata B.), Cleome (Cleome gynandra L.), tomato (Lycopersicon esculentum L.) and coriander (Coriandrum sativum L.). In addition, the effect of the test plants on P. xylostella adult olfactory responses, longevity and fecundity were investigated. In the field, each of the latter five test plants was intercropped with cabbage at Jomo Kenyatta University of Agriculture I' and Technology (JKUAT) farm and kale at Kenya Agricultural Research Institute (KARI-Matuga) and the P. xylostella infestation levels and damage assessed. Another field trial with different planting patterns of both cabbage and coriander was conducted at JKUAT to evaluate the most appropriate planting pattern for reducing P. <0.05) xylostella infestation. The effect of the companion crops on nontarget insects and important plant diseases was also evaluated on cabbage. Laboratory choice and no-choice tests indicated that Ethiopian mustard was found to be a preferred host for oviposition by P. xylostella while tomato was the least preferred for oviposition, as compared to other test plants. Choice tests also revealed that the number of eggs laid by the moths were significantly fewer on treatments of cabbage or kale combined with tomato, coriander or Cleome, when compared to those laid on sole-cabbage or kale. Larval percent survival was significantly lower ((P

This document is currently not available here.

Share

COinS