JACQUELYNE JEPCHUMBA ARUSEI

Pod borers, Helicoverpa armigera infestation is a key constraint affecting pigeon pea (Cajanus cajan) production. Development of pest resistance and expensive inputs and the fact that pigeon pea is a subsistence crop makes it difficult for farmers to adopt the use of synthetic pesticide. The objective of the study was to evaluate the response of pod borer against Bacillus thuringiensis isolates in the laboratory and determine the efficacy of Bacillus thuringiensis cry gene against the pigeon pea pod borer.  Soil samples from pigeon pea growing farms within Machakos and Makueni Counties were isolated with a selective method. The Bacillus thuringiensis isolates were grown on nutrient agar plates to establish colony features and subjected to gram reaction to ascertain the Bacillus thuringiensis morphological characteristics. Molecular detection of ten (10) Bacillus thuringiensis isolates were done using PCR with specific primers for Cry1 and Cry2 genes. The isolates were tested at different dilutions (10-1-10-6) for bioassay and bio efficacy experiment in the field to determine the virulence against pigeon pea pod borer. Larvae (2nd and 3rd instar) used for bioassay were reared in ITOC- ICIPE. Out of the 10 characterized isolates, two isolates, J7 and J10, displayed clear strong bands of Cry1 and Cry2 genes and were selected. The study shows that B. thuringiensis Cry1 and Cry2 can control pigeon pea pod borer, H. armigera both in the laboratory and field. Application of B. thuringiensis at higher concentration caused increased larval mortality of second instar larvae of H. armigera compared to third instar larvae. Therefore, timely application of B. thuringiensis isolate in controlling pigeon pea pod borer will facilitate reduction in its infestation hence increasing pigeon pea production.