Abstract
ABSTRACT The present study aimed to assess the effects of the essential oil of Croton pulegiodorus Baill on eight populations of Sitophilus zeamais Motschulsky with different patterns of susceptibility to synthetic insecticides. Populations of S. zeamais were obtained from Sete Lagoas-MG, Jacarezinho-PR, Bom Conselho-PE, Garanhuns-PE, Jupi-PE, Lajedo-PE, São João-PE and Serra Talhada-PE. To estimate the lethal concentrations (LC50 and LC90) of oil for each population, fumigation tests were performed. The susceptibility of S. zeamais to the essential oil varied among populations. Garanhuns and Bom Conselho was considered the susceptibility patterns, presenting the lowest LC50 (3.40 μL L-1 of air) and LC90 (9.60 μL L-1 of air) for the essential oil, respectively. The population from Jupi exhibited the highest LC50 (14.49 μL L-1 of air) and LC90 (19.60 μL L-1 of air) for C. pulegiodorus. The resistance ratio ranged from 1.84 for the São João to 4.26 for the Jupi population. Thus, the essential oil of C. pulegiodorus showed fumigant activity, causing mortality in all S. zeamais populations used.
Highlights
The maize weevil (Sitophilus zeamais Motschulsky, Coleoptera: Curculionidae) is one of the main stored-cereal pests around the world, being ubiquitous and responsible for great economic loss at post-harvest due to reduced grain quality, weight, and germination power of seeds (ALONSOAMELOT; AVILA-NÚNEZ, 2011)
The results of fumigation bioassays using the essential oil extracted from C. pulegiodorus indicate that there was significant variation in the response of S. zeamais populations to the toxicity of the essential oil, which implies different lethal concentrations for each population
By not including the value 1.0 in the confidence intervals of the ratios (ROBERTSON; PREISLER, 1992), except for Garanhuns-PE, the other seven populations evaluated showed a significant resistance ratio for the essential oil extracted from C. pulegiodorus
Summary
The maize weevil (Sitophilus zeamais Motschulsky, Coleoptera: Curculionidae) is one of the main stored-cereal pests around the world, being ubiquitous and responsible for great economic loss at post-harvest due to reduced grain quality, weight, and germination power of seeds (ALONSOAMELOT; AVILA-NÚNEZ, 2011). These losses are aggravated by improper storage methods and inadequate storage facilities which, together, result in severe damage to stored grains and, the aforementioned economic loss (NAPOLEÃO et al, 2013). The insecticidal effect of essential oils can be attributed to their chemical composition and mode of action on insects, causing them physiological changes, behavioral disorders, and mortality (CABALLERO-GALLARDO; OLIVERO-VERBEL; STASHENKO, 2011)
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