Determination of tannin activity and Paenibacillus alvei (Cheshire & Cheyne) Ash et al. (Bacillii: Paenibacillaceae) on the biocontrol of tannin-tolerant Agelastica alni L., 1758 (Coleoptera: Chrysomelidae) larvae

Abstract

Tannins are among the most abundant secondary metabolites synthesized by plants. Agelastica alni L., 1758 (Coleoptera: Chrysomelidae) is a critical forest pest. This study investigated the effect of Paenibacillus alvei (Cheshire & Cheyne) Ash et al. (Bacillii: Paenibacillaceae) and tannins against A. alni larvae. The larvae were collected from the Çayeli district of Rize province in 2022. In the feeding experiments, artificial diets containing 1.25%, 2.5% and 5% tannins were prepared. 100 and 200 µl of P. alvei were applied to the infected groups. Nutritional indices, pupal masses, phenoloxidase activities, antioxidant enzyme activities and mortality rates of larvae fed with different diets were studied. Relative consumption rate (RCR) increased with tannin concentration in all groups. Relative growth rate (RGR) increased with rising tannin concentrations across all groups. In the infected groups, the increase in tannin concentration caused a decrease in developmental time. While superoxide dismutase and phenoloxidase activities of uninfected larvae decreased with tannin concentration, catalase and glutathione peroxidase activities of larvae increased. In infected larvae, catalase activity decreased with increasing tannin concentration. The dose of P. alvei caused an increase in superoxide dismutase and phenoloxidase activities, but did not affect catalase and glutathione peroxidase activities. The diet containing 5% tannic acid had the lowest mortality rate.