Using Long-term Capture Data to Predict Trogoderma variabile Ballion and Plodia interpunctella (Hübner) Population Patterns

Estimating long-term spatial distribution of Plodia interpunctella in various food facilities at Rajshahi Municipality, Bangladesh, through pheromone-baited traps

The Indian meal moth, Plodia interpunctella (Hübner), feeds on a wide range of commodities in most regions of the world. The present study presents six years of monitoring data for P. interpunctella in pheromone-baited traps by analyzing the trends of spatial variability, in five food facilities located in the Rajshahi municipality area of Bangladesh. We also tracked insect incidence at different spatial scales and evaluated the impact of food facility types and storage structures on insect populations. Our model showed an aggregated distribution pattern for P. interpunctella. Population patterns of P. interpunctella varied significantly among facilities. The highest number of moths captured was recorded in a grain retailer located at Municipal market, followed by a grain warehouse at Harian, pulse mill at Kazla, flour mill at Sapura and grocery shop at Katakhali. The population fluctuation of P. interpunctella moths was similar among the different locations tested, while there were no captures during the winter period. Our results indicate that long-term monitoring in a wide range of areas can be used to indicate population outbursts, under an area-wide management strategy.

Trapping Tribolium castaneum (Coleoptera: Tenebrionidae) and Other Beetles in Flourmills: Evaluating Fumigation Efficacy and Estimating Population Density

Simple Summary

The red flour beetle and several other beetle pests consume post-harvest grains and grain products, and are serious pests of flourmills. Fumigation with gaseous pesticides is commonly performed in flourmills. However, fumigation is very dangerous and expensive, and it may not be needed if pest populations are very small. This project used pheromone-baited traps to capture beetles and monitor the pest populations over a two year period in flourmill 1 and a one year period in flourmill two. Traps give information about the relative population size over time at a mill and the variation in beetle numbers across different spaces of the mill. Trapping at both mills found that beetles occurred at similar numbers of beetles per trap across all the locations in the mill, but there were large differences in numbers of beetles over time. However, fumigation did not always show elimination or large reductions in beetle populations when comparing numbers trapped before fumigation with number trapped after fumigation. Traps can therefore give information about the success of a fumigation in reducing or eliminating a pest population. Numbers of beetles caught in traps do not provide the actual density or size of pest populations in food. Analysis of data at one mill compared numbers of beetles caught in traps with numbers of beetles sifted from known amounts of flour milled at the same times. That comparison showed that beetle numbers in traps increased or decreased at the same times that beetle number in the flour also increased or decreased. This research suggests that using pheromone traps for red flour beetles and other pests provide good estimates of pest population sizes to help in decisions about pest control in flourmills.

Abstract

This paper reports beetle pests common to flourmills targeted during a series of trapping studies over a two-year period in flourmill 1 and a one year period in flourmill 2. Objectives were (1) use pheromone-baited traps to detect T. castaneum (Herbst) and other pest species present for their distribution over space and time, (2) monitor T. castaneum activity before and after fumigations to assess efficacy of the treatment, and (3) correlate counts of T. castaneum via trap capture against direct T. castaneum counts from samples of the milled flour to assess the value of trap data to estimate relative size of the pest population. Traps were deployed in two different flourmills over two consecutive years. T. castaneum was the most commonly trapped beetle during both years in mill 1. In mill 2, Typhaea stercorea (L.) and Cryptolestes ferrugineus (Stephens) were both captured in higher numbers than T. castaneum. In mill 1, trap capture was higher overall during Year 2 for most of the species compared with capture during Year 1, likely due to a dust cover modification made for the pitfall trap used in Year 2. Trap capture was also evaluated by location within the mills and a significant difference was found in the capture of T. stercorea during both years in mill 1. T. castaneum captures were significantly reduced following most fumigations, which used methyl bromide in milling areas and phosphine in bulk-stored finished flour. However, in most cases trap catches showed that beetle populations were not eliminated. Trap captures after fumigation suggest either that the fumigations were not entirely effective, or that full grown adult beetles were entering the mill soon after fumigation. When captures of T. castaneum from traps in two spaces of mill 1 during Year 2 were compared with counts of beetles from samples of siftings collected in the finished flour, the correlation coefficients were nearly significant for both sets of traps.

Mobility and Dispersal of Two Cosmopolitan Stored-Product Insects Are Adversely Affected by Long-Lasting Insecticide Netting in a Life Stage-Dependent Manner

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and Trogoderma variabile Ballion (Coleoptera: Dermestidae) are two stored-product insects that cause extensive damage to a variety of postharvest commodities. Long-lasting insecticide-incorporated netting (LLIN), commonly used to control vector-borne diseases in tropical regions, has only been recently studied in an agricultural setting. While prior research showed that LLIN was successful against stored-product beetles, little is known about differential susceptibility among stored-product insect life stages. The aim of this study was to evaluate LLIN efficacy against immature T. castaneum and T. variabile compared with adults. Movement and dispersal ability were evaluated after exposure to LLIN or an untreated, control netting. For the movement assay, video-tracking software recorded the postexposure effects of LLIN on distance traveled and velocity of the insects in 2-h trials. For the dispersal assay, insects were exposed to the netting then released into one end of a PVC pipe and allowed 48 h to disperse to a novel food patch located at the opposite end of the pipe. Our study found that movement and dispersal ability of T. variabile and T. castaneum are significantly reduced, often by multiple-fold, after LLIN exposure, with the larval stage of each species more tolerant to the insecticide netting than adults. These results indicate that LLIN is a promising tool for use in intercepting immigrating insects of different life stages in food facilities to protect stored products.

Species Composition, Temporal Abundance and Distribution of Insect Captures Inside and Outside Commercial Peanut Shelling Facilities

Insect populations were studied within two commercial peanut shelling facilities located in the southeastern United States. Commercially available pheromone/kairomone-baited dome traps and pheromone-baited flight traps were deployed throughout processing and shipping portions of the shelling plants and serviced weekly over one year. Lasioderma serricorne, Tribolium castaneum, Typhaea stercorea, Carpophilus spp., Plodia interpunctella and Cadra cautella were the most common captures across locations. Lasioderma serricorne made up 87% and 88% of all captures in dome traps in plants one and two, respectively. While L. serricorne was not captured during the winter months in flight traps, it was captured with near 100% frequency in dome traps, suggesting that populations persisted throughout the year inside the facilities. Tribolium castaneum populations were active year round. Across insect species and trap type, temperature was a significant covariate for explaining variation in insect counts. After accounting for the effect of temperature, there were always more insects captured in the processing portions of the facilities compared to the shipping areas. A negative linear relationship was observed between captures of L. serricorne and T. castaneum and trap distance from in-shell peanuts entering the shelling facilities. Conversely, fungivores were more evenly distributed throughout all parts of the shelling plants. These data suggest that management efforts should be focused where in-shell peanuts enter to reduce breeding and harborage sites for grain feeding insects.