Diatomaceous earth against Ecuadorian populations of the maize weevil (Sitophilus zeamais)

Abstract

Diatomaceous earth (DE) is an inert dust derived from unicellular algae, which is effectively used as an insecticide. The DE efficacy has been recognized against a range of stored grain insects including the maize weevil (Sitophilus zeamais, Motschulsky, 1885). However, little is known about the effect of DE among maize weevil populations exposed to different doses, particularly regarding its potential effects on mortality, repellence, progeny emergence, and grain consumption. Thus, we assessed DE (83.97% SiO2) effects of three Ecuadorian maize weevil populations (Buena Fe, Mocache, Quevedo) exposed to different DE doses (0, 1, 3, 5 g DE/kg of maize). As expected, the three DE doses were able to effectively control the insects (P = 0.05) with the median survival times (LT50) ranging from 5 to 9 days (120.00–216.00 h). No DE repellence was detected in the three maize weevil population, regardless of the dose used suggesting that DE is not recognized by the adult weevils. The DE doses applied against maize weevil led to reduction on the progeny production of S. zeamais (χ2 = 235.77, df = 1, P < 0.001) and compromised their grain consumption (F1,174 = 20.65, P < 0.001). However, no differences were found among the three weevil populations. These findings reinforce the use of DE as an alternative in management programs for S. zeamais populations.