Seasonal infestation of mango leaf cutting weevil and its response to some weed extracts

The seasonal abundance of mango leaf cutting weevil (Deporaus marginatus Pascoe) was studied on nine varieties of mango viz. Amropali, Harivanga, Mallika, Surjapuri, Gopalvog, Langra, Fazli, Ashwina and Guti during October 2016 to September 2017 in the orchard of Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh. In this study toxicity of some weed extracts namely black nightshade, wild tobacco, leucas, lantana, goatweed and raan tulas were evaluated on the weevil. Rresults showed that the highest percentage of infestation was found in Surjapuri (average 52.6%), and the lowest in Ashwina (average 33.4%). In regards to month, maximum infestation was found in August (77.5%) at surjapuri and minimum was in February (7.9%) at Mallika. No infestation was observed on the mango leaves during December and January. The highest toxicity effect (average mortality 78.3 %) was found in rann tulas at 5.0 % concentration, whereas black nightshade showed the lowest toxicity effect (average mortality 10.8 %) at 1.25 % concentration. On the basis of mortality, the order of toxicity of the plant extracts were found rann tulas > wild tobacco > lantana > goat weed > leucas > black nightshade. Adult’s mortality were directly proportional to different concentration levels and hours after treatments (HAT). The lowest LD50 values (3.3, 2.3 and 1.8 mg/ml at 24, 48 and 72 HAT) of rann tulas indicated its highest toxicity effects against D. marginatus. The present study revealed that synthetic pesticides can be replaced with botanicals for the management of D. marginatus in order to save the environment.