Biological characteristics and efficacy of Bacillus thuringiensis var. thuringiensis against the cotton leaf roller, Syllepte derogata (Fabricius, 1775) (Lepidoptera: Crambidae)

Abstract

Cotton (Gossypium hirsutum L.) is an important fiber crop cultivated in > 50 countries of the world. The cotton leaf roller Syllepte derogata (Fabricius, 1775) (Lepidoptera: Crambidae) is considered as an invasive and widespread species in many geographic regions of the world and pose significant damages to cotton crop. This study reported the first record of S. derogata and its biological characteristics in Azerbaijan. The results indicated that S. derogata was only observed on cotton crop from the Absheron region of the country. The larvae only attacked on cotton leaves and did not damage the reproductive organs (i.e., bolls). S. derogata completed one generation in 31–42 days in the Absheron region. Larvicidal efficacy of Bacillus thuringiensis var. thuringiensis (Btt) against S. derogata was also tested under laboratory and field conditions. Three different Btt concentrations (0.3, 0.4, 0.5 g/l) were tested against 2nd and 4th larval instars of S. derogata. The 0.5 g/l concentration of Btt caused 72.88% larval mortality under field conditions. However, under laboratory conditions, 0.3, 0.4, and 0.5 g/l concentrations caused 50, 66.67, and 100% mortality of the 2nd instar larvae on the 7th day, respectively. The 0.5 g/l suspension of Btt proved the most effective against S. derogata; therefore, it can be recommended for the management of S. derogata in the infested region of the country. This study further warns that S. derogata could spread to the other cotton-producing regions of the country; thus, an effective early warning and rapid response system must be developed for the pest in the country.