Potential for using Datura alba leaf extracts against two major stored grain pests, the khapra beetle Trogoderma granarium and the rice weevil Sitophillus oryzae

Various plants are well known for their insecticidal activity and their use was maintained for millennia throughout all the agricultural regions of the world. In a current context, the use of Botanical insecticides represents one of the best alternatives to chemicals for the development of environmentally-friendly strategies for stored grain pest control. Datura alba Nees is a plant found extensively in the warmer regions of the world and it is used as a medicinal plant. The present study aims to assess the contact toxicity and the transgenerational effects of D. alba leaf extract (DLE) against two important insect pests on stored rice, Trogoderma granarium and Sitophilus oryzae, under laboratory conditions. Filter papers were soaked in three DLE concentration solutions and in two control treatments: water and acetone. The survivor specimens (F0) were transferred to a new untreated feeding substrate and the population build up of the two following generations (F1 and F2) were counted after 30 and 60 days respectively. The highest DLE concentration (2.5%) induced the significantly highest mortality with 33.5% and 45% mortality in T. granarium and S. oryzae after 7 days of exposure respectively. The DLE long-term effect towards both tested species was also proved by the high demographic decrease in the F2 generations, when compared to control groups. This study is the first step towards establishing a scientific basis for the effective application of D. alba plant materials as bio-rational tools to control stored grain pests.