Insecticidal effect of diatomaceous earth and dolomite powder against Corn weevil Sitophiluszeamais Motschulsky, 1855 (Coleoptera: Curculionidae)

Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae) which develops inside the grain, is an aggressive pest of stored grains. Here, we evaluated the efficiency of diatomaceous earth (DE), Diatomita CI/325 CX, and dolomite (DOL), Dolomita Dr. Kanyo, against S. zeamais reared on corn under laboratory conditions and observed external alterations on treated insects using scanning electron microscopy (SEM). Insects treated with both DE and DOL were impregnated with particles on the body surface, and they showed 100% mortality after 10 days of exposure. Damages caused by inert dusts may have contributed to dehydration and desiccation, consequently, leading insects to death. Thus, diatomaceous and dolomite were effective against S. zeamais under laboratory conditions.

Establishment and control of Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae) with inert dusts in stored canola

Tribolium castaneum (Herbst, 1797) is know as one of main pests of stored canola seeds worldwide, however, the cases of infestation in Brazil are still not reported. Due to its potential pest status allied to the increasing production of canola in Brazil, this work aims to evaluate the establishment of T. castaneum in canola stored seeds, as well as the effects of diferent inert dusts to its control. For stablishment determination, three substrates were tested: wheat bran (control); whole wheat seeds; and whole canola seeds. The insects remained in the substrates for 14 days, when mortality was counted, and then for aditional seven days before get removed, for progeny assessment at 66 days after initial exposure. For the insecticide potential of inert dusts, four treatments were tested in canola seeds as substrate: diatomaceous earth; basaltic rock powder; vegetable charcoal powder; and untreated canola seeds as control treatment. The beetles were exposed to the treated substrate and cumulated mortality was counted each two days for 15 days. Lower adult mortality and higher progeny in canola seeds indicates that these substrate is a potential host for T. castaneum. Diatomaceous earth and vegetable charcoal powder reduced the survival of adult beetles in canola in more than 60% at the end of the evaluation period. The T. castaneum adults and its offspring develops well in stored canola seeds. Additionally, the use of inert dusts, mainly diatomaceous earth and vegetable charcoal powder presents promising results of control of the beetle in stored canola seeds.