Bioassay of Bacillus thuringiensis toxins against two major coffee pests, i.e. coffee berry borer (Hypothenemus hampei) and coffee white stem-borer (Xylotrechus quadripes)

H. hampei and X. quadripes are both endocarpic coleopteran insects difficult to control by conventional means. The transgenic approach may represent an efficient complement to traditional pest control strategies. Trangenic coffee plants would be adapted to the control of borers since the insecticidal toxin produced by the plant would be present within the tissues on which the pest feeds. Bioassay procedures based on artificial diet were developped on H. hampei and X. quadripes for estimating the insecticidal activity of B. thuringiensis which is the most important source of genes for the development of pest-resistant transgenic plants. Artificial diets for H. hampei and X. quadripes have been standardized. Bioassays were conducted with 2nd instar larvae for H. hampei and with neonates for X. quadripes. Mortality was counted one week after the B. thuringiensis spores-crystals applications. Several B. thuringiensis isolates potentially active against coleopteran were tested for toxicity against both targeted pests. [Texte intégral