A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development

Thesis (M.Sc.) - Asian Institute of Technology, 1999

A field experiment was carried out in Lao PDR from January to March 1999 to study the feasibility of using Bacillus thuringiensis (Bt) for diamondback moth (DBM) control in cabbage. There were three treatments, namely, local practice, in which the crop sprayed with insecticides, once and twice a week, and in IPM treatment when Bt was used. Fields with and no insecticide spray were used as control. Information from before and after spraying was made using 10 fixed plants at random of 10 plants per plot. The field experiment showed that Bacillus thuringiensis is as effective against DBM as chemical insecticides. Bt does not harm the parasitoids and predators of DBM as do chemicals. Many kinds of predators and parasitoids including larval parasitoids were found in the experimental field. The major pests are diamondback moth (DBM), cutworms, cabbage webworms, aphid, and flea beetles and some diseases such as club root, rot blight, and Atlernaria leaf spot. The experiment filed also indicated that cabbage cultivates were not well adapted to local conditions. Results from the survey involving extension, agricultural officers and farmers showed that the current farmers' practices for controlling DBM was mainly chemical insecticides, followed by cultural and manual control practice. Microbial control has not been widely applied. Insecticides used to control DBM are highly hazardous and moderately hazardous. Farmers frequently exceed recommended concentrations in using chemicals and mix two or more in a single spray. The initial applications are usually in the vegetative period to young heading and continued at fixed intervals until maturation. The extension services are weak with little direct contact with farmers.