Abstract

The Angoumois grain moth, Sitotroga cerealella (Olivier, 1789) (Lepidoptera: Gelechiidae), is primarily a pest of stored products, that feeds inside the grain as larvae inducing significant economic loss in various stored commodities. Our previous studies proved that garlic essential oil and its active substances inhibit oviposition in moths. To further explore the effect on reproductive behavior and accurately interpret the results in terms of effective control of the moth population, moths were treated with diallyl trisulfide (DATS), an active substance of garlic essential oil, at a dose of 0.015 µL/L in air (LC20, sub-lethal concentration). The results showed that fecundity and the proportion of viable eggs significantly decreased when the moths were treated with LC20 DATS. Furthermore, female circadian mating rhythms and calling periodicity changed significantly after treatment. Compared with controls, the peak in mating occurred approximately 1 h earlier on the first day after DATS treatment, while it was significantly later on days 2 and 3. Moreover, mating frequency declined in presence of DATS compared with the controls. The percentage of females engaging in calling behavior decreased significantly with time, to less than 50%, 2 days after treatment, while a high calling percentage (>80%) was recorded for control moths on all 4 days. In addition, DATS had an inhibitory effect on the mating duration of S. cerealella. Moreover, a significant reduction was observed in the amount of sex pheromones extracted 8 h and 9 h after treatment. Our findings suggested that DATS has the potential to manipulate the moth population at LC20 and would be an efficient alternative to synthetic insecticides for the control of pests having low toxicity to non-target organisms and ecosystems.

Highlights

  • Larvae of the Angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), primarily feed inside stored grains, and are serious pests worldwide [1]

  • The purpose of this study was to: (1) determine the effect of diallyl trisulfide (DATS), a major component of garlic essential oil, on the fecundity of S. cerealella; (2) detect anomalies in the mating behavior of moths treated with DATS; (3) assess the influence of DATS on the circadian mating and calling rhythms of females, and mating frequency and duration; and (4) produce a preliminary estimate of the effect of DATS on the amount of sex pheromones secreted by female S. cerealella

  • The number of eggs laid by females treated with DATS was significantly lower than that laid by control females (Figure 1A)

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Summary

Introduction

Larvae of the Angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), primarily feed inside stored grains, and are serious pests worldwide [1]. Chemical controls are the most effective tools for pest management in stored grains. The chemical control of S. cerealella is unsatisfactory, due to chemical resistance and resulting residues in stored grains [2,3]. Insects 2020, 11, 21 insecticides, there is an urgent need to find alternative methods to those based on conventional pesticides [4]. Behavioral manipulation, such as manipulation of reproductive behavior has received widespread attention to control some crop/wood-boring pests [5]. Reproductive behavior, which integrates behavioral and physiological events in both sexes, including sex recognition, courtship, mating, and female post-mating behavioral changes, can be influenced by the environment [6]

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