Combination of Methoprene and Controlled Aeration to Manage Insects in Stored Wheat

Samuel Liu,Douglas Vangundy,Frank Arthur,Thomas Phillips

doi:10.3390/insects7020025

Abstract

A commercial formulation of the insect growth regulator methoprene was applied to wheat stored in small bins either alone or in combination with controlled aeration of the bins, to lower grain temperature for insect pest management of stored wheat. Grain temperatures were monitored and modified by a computer-controlled thermocouple system that also activated the aeration system at programmed set-points to move cool ambient air through the grain mass to lower grain temperature. Results from sampling insect populations in experimental storage bins along with laboratory mortality bioassays of insects placed on wheat taken from the bins over the course of the storage period showed that methoprene was very effective in controlling infestation by the externally-feeding stored grain insects Plodia interpunctella (Hübner), the Indian meal moth Tribolium castaneum (Herbst), the red flour beetle, Cryptolestes ferrugineus (Stephens), the rusty grain beetle, and also for the internal-feeding pest Rhyzopertha dominica( Fauvel), the lesser grain borer. Methoprene did not give good control of the internal-feeding pest Sitophilus oryzae (L.), the rice weevil. Aeration alone was somewhat effective in suppressing insect population development, while methoprene alone or when combined with aeration greatly enhanced insect control. Commercial grain grading for industry quality standards at the end of the storage period confirmed the impact of insect suppression on maintaining high quality of the stored wheat. This field experiment shows that methoprene combined with aeration to cool grain can be effective for pest management of stored wheat in the southern plains of the United States of America.

Highlights

The insect growth regulators (IGRs) are insecticides that mimic insect molting hormones and interfere with normal immature insect development [1,2,3]
Controlled aeration applied to the small bins of wheat for two of the treatments, eight bins total, caused a distinct cooling of grain when compared to grain temperatures for the eight bins without any aeration (Figure 1)
The work demonstrates the residual activity of methoprene as an IGR during grain storage and the results suggest that methoprene can reduce pest population increases and associated grain damage over time

Summary

Introduction

The insect growth regulators (IGRs) are insecticides that mimic insect molting hormones and interfere with normal immature insect development [1,2,3]. IGRs include juvenile hormone analogues (JHAs) which are considered biopesticides because they generally have very low mammalian toxicity and can have limited impacts on non-target arthropod species [4]. IGRs interfere with insect metabolism in a manner that disrupts normal growth and development. The insect dies before it reaches full maturity. Insect growth regulators are typically selective for insects and can either inhibit the synthesis of chitin required for forming new cuticle at each molt, or disrupt or replace the production of juvenile hormones that regulate the molting process [5,6,7].

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