Artificial Selection to a Nonlethal Cold Stress in Trogoderma variabile Shows Associations With Chronic Cold Stress and Body Size

Extreme temperature has been used as an alternative to chemical treatments for stored product pests for years. Resistance to heat or cold treatments has not been documented in stored product insects, but repeated use of ineffective treatments could lead to adaptive tolerance. Trogoderma variabile (Dermestidae) is a common pest of stored products, and the larval stage is highly resistant to cold and destructive. We artificially selected populations by inducing chill coma at four different cold temperature treatments: 3 and 5 h at −10°C and 3 and 5 h at 0°C. Recovery time was highly heritable after selection for seven generations for decreased recovery time (cold tolerance) and increased recovery time (cold susceptibility) at all time and temperature combinations. Three replicate populations for each time and temperature combination varied substantially, suggesting different mutations in each population were probably responsible for selected phenotypes. Body size decreased in populations selected for cold susceptibility compared with those selected for cold tolerance and survivorship to long-term cold stress increased in the cold-tolerant populations compared with the susceptible populations. After the cessation of the selection experiment, cold tolerance dissipated within four generations from the populations at −10°C, but was maintained in populations exposed to 0°C. Our results suggest that warehouse beetles can adapt to cold stress quickly, but in the absence of cold stress, the proportion of cold-tolerant/susceptible individuals is quickly reduced, suggesting that some of the mutations responsible for these phenotypes may be associated with fitness costs under normal conditions.

Methyl Benzoate as a Putative Alternative, Environmentally Friendly Fumigant for the Control of Stored Product Insects

Historically, stored product insect pest management has been based around the use of methyl bromide and phosphine as fumigants. However, methyl bromide has been phased out for structural fumigations, and there is increasing worldwide insecticide resistance to phosphine. One potential alternative, environmentally friendly option is the use of methyl benzoate (MBe), which is considered a food safe compound. In this study, we evaluated the direct and sublethal effects of MBe exposure on the survivorship and mobility of four stored product species with diverse life histories, including Rhyzopertha dominica, Tribolium castaneum, Sitophilus zeamais, and Trogoderma variabile. Sets of insects were exposed to a control, low, or high MBe concentrations in flasks with or without food for 24 or 72 h in the laboratory. Furthermore, we assessed phosphine exposure under similar conditions. Overall, R. dominica was the most susceptible to MBe exposure, followed by T. castaneum. By contrast, S. zeamais and T. variabile were relatively unaffected by MBe exposure. Exposure to MBe induced multiple-fold decreases in the total distance moved and velocity of adults still considered alive or affected after assays. By comparison, phosphine effectively killed all individuals of all species. Our data suggest that while MBe was effective for R. dominica, it was not competitive in comparison to phosphine for controlling susceptible strains of these species at the specified experimental conditions.

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

Insects can infest facilities that house and process post-harvest grains and grain-based products. Integrated pest management tactics rely on tracking insect populations and using this information to select and target management tactics. Our ability to predict when and where to best focus treatment relies on an understanding of long-term trends, but often any available monitoring data are limited in its duration. Here we present data collected over a 10-year period at a flour mill in the central part of the United States. Using traps placed both inside and outside a flour mill and baited with pheromone-lures for Plodia interpunctella (Hübner), Indianmeal moth, and Trogoderma variabile Ballion, warehouse beetle, we examine environmental and spatial variability in insect captures. We find that both species, inside and outside the mill, are highly influenced by seasonal patterns, with peaks of insect captures during the warm season (April through September). There is also consistency across time and space in trap capture for P. interpunctella with traps in an open location consistently capturing high numbers of insects. In contrast, T. variabile lacked consistency in trap capture but were most often not found in the same trap locations as P. interpunctella. Fumigations conducted within the facility appeared to have little impact on insect captures inside, with dynamics appearing to be driven more by broader seasonal patterns in activity. These data and analyses suggest that there is a larger population of these insects that are readily moving in and out of the structures, while fumigation treatments are only impacting a small portion of the overall population and tactics targeting immigration may be an important addition to the pest management program.

NEW RECORDS OF ALLOCHTONOUS, INVASIVE AND PEST INVERTEBRATE SPECIES FROM THE REPUBLIC OF MACEDONIA

In this paper new data on allochtonous and invasive invertebrate species: Arion (Arion) cf. vulgaris Moquin-Tandon 1855, Cornu aspersum (O.F. Muller, 1774), Harmonia axyridis (Pallas, 1773), Acanthoscelides obtectus (Say, 1831), Trogoderma variabile Ballion, 1878, Stegobium paniceum (Linnaeus, 1758), Oxycarenus (s.str.) lavaterae (Fabricius, 1787), Corythucha ciliata (Say, 1832), Leptoglossus occidentalis Heidemann, 1910, Ceroplastes japonicus (Green, 1921), Pseudaulacaspis pentagona (Targioni Tozzetti, 1886) MacGillivray, 1921, Tuta absoluta (Meyrick, 1917) and Frankliniella occidentalis (Pergande, 1895) from Macedonia are presented. The study represents faunistic data synthesis from different parts of Macedonia, based on collecting efforts of several taxonomic experts. The results of the study help to outline the composition of non-native and invasive invertebrate fauna and to narrow gaps concerning the knowledge of their distribution and introduction in Macedonia.

Trogoderma variabile Ballion, 1878: a possible new pest of Italian entomological collections (Coleoptera: Dermestidae)

The first infestation of an entomological collection in Italy by <em>Trogoderma</em> <em>variabile</em> Ballion, 1878 is recorded; it was detected in Rome in 2014. This record and another one from the Molise Region, are herein discussed. Distributional, biological and nomenclatural data on this polyphagous alien pest are summarized, and its possible local establishment is discussed.