Bioactivity of Some Botanical Powders against Wheat Weevil, Sitophilus granarius (L.) (Coleoptera: Curculionidae), and Confused Flour Beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae)

Abstract

Stored-product pests attack cereal grains and legume seeds post-harvest. They not only damage the grain but also decrease its weight and quality. Therefore, the aim of the present study was to investigate the bioactivity of resin powders extracted from Pistacia lentiscus L. bark, Boswellia carterii birdwood bark, and Elettaria cardamomum seeds against two of the most important stored-product pests, Sitophilus granarius (L.) and Tribolium confusum Jacquelin du Val. We used three bioassay methods, repellent effect, reduction of progeny, and grain weight loss and investigated the effects of the powders on the life cycles of the insects. Wheat grains were mixed with the three botanical powders separately, at different concentrations (3, 5, 7, and 10 % w/w). Sitophilus granarius and T. confusum were fed these mixtures. Repellent activity was examined after 2, 4, 8, 12, and 24 h. The E. cardamomum powder displayed the maximum repellent activity (100 %) against both S. granarius and T. confusum after 24 h at 3 % concentration. The P. lentiscus powder reached maximum repellent activity (80 %) against S. granarius and T. confusum at 7 % concentration after 12 h and 24 h, respectively. The B. carterii powder achieved maximum repellent activity against S. granarius and T. confusum (73.3 % and 86.7 %) at 10 % concentration after 24 h and 12 h, respectively. No progeny was produced in grains treated with 3 % P. lentiscus powder, 7 % E. cardamomum powder, or 7 % B. carterii powder. Thus, protection against both beetles started from 3 % concentration when P. lentiscus powder was used and from 7 % and 10 % (against S. granarius and T. confusum, respectively) when E. cardamomum powder was used. A 7 % B. carterii concentration completely saved the grains from S. granarius damage, and a 10 % concentration offered 99.5 % protection against T. confusum. However, all tested powders significantly affected all the studied parameters (life cycle and grain weight loss). The results show that the three botanical powders provide high repellent activity against S. granarius and T. confusum, which might be useful in protecting stored grains from these insects.