Abstract
Rhyzopertha dominica (Fab.), the lesser grain borer, and Sitotroga cerealella (Olivier), the Angoumois grain moth, are internally feeding stored product insects that can infest raw grains. In this test, brown rice was treated with 0.5 and 1.0 ppm of a new emulsifiable concentrate (EC) formulation of the pyrethroid deltamethrin and stored for 12 months. One day after treatment, and every 3 months for 12 months, treated rice was mixed with untreated brown rice in the following ratios: 0:100 (untreated controls), 10:90, 25:75, 50:50, 75:25, and 100:0 (all treated). Bioassays were conducted by exposing 10 parental adults of each species on the rice mixtures and assessing progeny production, feeding damage, and weight loss. The progeny of S. cerealella ranged from 105.6 F1 adults on untreated brown rice to 69.4 F1 adults on 100% treated rice, but there was little feeding damage or weight loss. The progeny production of R. dominica declined from 177.4 F1 adults on untreated rice to 9.8 F1 adults on 100% treated rice. Weight loss and feeding damage were correlated with progeny production. The results show that the new deltamethrin formulation could be used for protection of brown rice, but S. cerealella may be less susceptible to deltamethrin compared to R. dominica.
Highlights
Rice is cultivated in the south-central United States (USA), principally in Arkansas, southwesternLouisiana, eastern Texas, extreme southeast Missouri, parts of Mississippi on the eastern side of the Mississippi river, as well as in the northern part of the central valley of California [1]
These include Storicide II®, which is a mixture of 3 ppm of the organophosphate chlorpyrifos-methyl and 0.5 ppm of the pyrethroid deltamethrin, Centynal®, which contains 0.5 ppm of deltamethrin, Diacon IGR+®, which is a mixture of the insect growth regulator (IGR) methoprene and either 0.5 or
An initial analysis showed that species, deltamethrin rate, mixture percentage, and month significantly affected progeny production, with p < 0.001 (F = 15.1, df = 1587; F = 10.9, df = 1,587; F = 45.0, df = 5587; F = 5.3, df = 4587, respectively)
Summary
Eastern Texas, extreme southeast Missouri, parts of Mississippi on the eastern side of the Mississippi river, as well as in the northern part of the central valley of California [1] It can be stored as rough (paddy) rice in bins or elevators or as milled rice (either white or brown) in bulk storage or in bags. In the USA, several insecticides are registered for direct application to rough rice and brown rice These include Storicide II® , which is a mixture of 3 ppm of the organophosphate chlorpyrifos-methyl and 0.5 ppm of the pyrethroid deltamethrin, Centynal® , which contains 0.5 ppm of deltamethrin, Diacon IGR+® , which is a mixture of the insect growth regulator (IGR) methoprene and either 0.5 or. Females of R. dominica or S. cerealella lay eggs on the exterior of a grain kernel, and the larva hatches and bores into the kernel, where it completes development to the Insects 2019, 10, 95; doi:10.3390/insects10040095 www.mdpi.com/journal/insects
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