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

• Main Authors: Carl W. Doud, Gerrit W. Cuperus, Phillip Kenkel, Mark E. Payton, Thomas W. Phillips
• Format: Article
• Language: English
• Published: MDPI AG 2021-02-01
• Series: Insects
• Subjects: red flour beetle; <i>Typhaea stercorea</i>; <i>Cryptolestes ferrugineus</i>; pheromone; traps; stored products
• Online Access: https://www.mdpi.com/2075-4450/12/2/144

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 <i>T. castaneum</i> (Herbst) and other pest species present for their distribution over space and time, (2) monitor <i>T. castaneum</i> activity before and after fumigations to assess efficacy of the treatment, and (3) correlate counts of <i>T. castaneum</i> via trap capture against direct <i>T. castaneum</i> 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. <i>T. castaneum</i> was the most commonly trapped beetle during both years in mill 1. In mill 2, <i>Typhaea stercorea</i> (L.) and <i>Cryptolestes ferrugineus</i> (Stephens) were both captured in higher numbers than <i>T. castaneum</i>. 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 <i>T. stercorea</i> during both years in mill 1. <i>T. castaneum</i> 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 <i>T. castaneum</i> 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.