Efficacy of low temperatures for the control of all life stages of Plodia interpunctella and Liposcelis bostrychophila

The insecticidal effect of low temperatures for the control of all life stages of two stored-product insects, Plodia interpunctella and Liposcelis bostrychophila, was evaluated under laboratory conditions. The temperatures tested were 0, − 5, − 10 and − 15 °C, and, at these temperatures, the insects were exposed for 2, 4 and 8 h and also for 1, 2, 3 and 7 days. Regarding P. interpunctella, the most cold-tolerant life stage was larvae, given that 2 days of exposure were needed for complete (100%) mortality at − 10 °C. Moreover, all larvae were dead at − 15 °C even after 2 h of exposure. Eggs of P. interpunctella were susceptible to cold, as mortality was complete after 7, 1 day, 2 and 2 h at 0, − 5, − 10 and − 15 °C, respectively. L. bostrychophila was by far less susceptible than P. interpunctella. For this species, adults were still alive even after 7 days at − 10 °C, while complete mortality was achieved only after 1 day at − 15 °C. Eggs of L. bostrychophila were the most cold-tolerant life stage, as survival was observed even after 3 days at − 15 °C. The results of the present study provide the first data set on which all life stages of P. interpunctella and L. bostrychophila are evaluated for their susceptibility to cold treatments in a standardized series of exposures and temperatures. These results are expected to further encourage the “real world” application of cold treatments for the disinfestation of durable stored-products. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature

To Acclimate or Not to Acclimate? Simultaneous Positive and Negative Effects of Acclimation on Susceptibility of Tribolium confusum (Coleoptera: Tenebrionidae) and Oryzaephilus surinamensis (Coleoptera: Silvanidae) to Low Temperatures

Laboratory tests on acclimated and nonacclimated life stages of Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) (adults, pupae, larvae, and eggs) and Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) (adults, larvae, and eggs) were conducted at 0, -5, -10, and -15°C to evaluate effects of acclimation on susceptibility to cold treatment. Acclimation of all tested life stages for 7 d at 15°C affected susceptibility of both species to the cold temperatures. After 1 d exposures for ≥2 h, acclimated adults had a noticeable increase in cold tolerance compared with nonacclimated adults for both tested species. Nonacclimated pupae of T. confusum were equally susceptible to cold compared with acclimated pupae at short exposures to low temperatures. Exposure of nonacclimated life stages of T. confusum, at -10°C for 1 d gave 0% survival. Similarly, almost all (99.6%) nonacclimated individuals of O. surinamensis died at -10°C. At 0°C, nonacclimated larvae were more cold tolerant than acclimated larvae, but this trend was reversed when larvae were exposed to -5°C. Mixed results were obtained for larvae of O. surinamensis because in some of the combinations tested, nonacclimated larvae were more tolerant, even at temperatures that were lower than 0°C. In contrast to O. surinamensis, eggs of T. confusum that had not been exposed to cold were not affected by acclimation, while exposure to cold showed increased cold hardiness in acclimated eggs. Results show that individual stored-product insect species may have mixed susceptibility to cold temperatures, which must be taken into account when using cold treatment as a management strategy. © 2019 The Author(s). Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved

Influence of the presence of flour on the efficacy of low temperatures against stored product insects

The efficacy of low temperatures ranging from 0 to −15 °C was evaluated against all life stages of Tribolium confusum, adults of Oryzaephilus surinamensis and adults of Liposcelis bostrychophila. All species/life stages were exposed in empty vials or vials containing 5 g of flour, for time intervals of 2–7 d. Eggs and pupae were the least susceptible life stages of T. confusum, as these life stages had the highest survival at – 15 °C. Nevertheless, at this temperature, an exposure of 4 and 8 h for eggs and pupae, respectively, resulted in no survival. In most combinations, the presence of flour did not affect survival of T. confusum exposed to any temperature. There was no survival of O. surinamensis adults after exposure to −5 °C for 7 d or to −10 °C for 8 h, and the presence of flour had no effect on survival. Adults of L. bostrychophila were the most-cold tolerant among the species and life stages tested; at −10 °C, mortality was 100% only after 7 d of exposure. For this species, the presence of flour had some effect on adult survival, but results were not consistent with temperature. The results of this study can be utilized to develop control programs for using low temperatures as a disinfestation strategy for infested commodities. © 2020 Elsevier Lt

Susceptibility of different life stages of tribolium confusum (Coleoptera: Tenebrionidae) and oryzaephilus surinamensis (Coleoptera: Silvanidae) to cold treatment

Laboratory tests were carried out to examine the efficacy of different exposure intervals (2 h, 4 h, 8 h, 1 d, 2 d, 3 d, and 7 d) on different life stages (adults, pupae, larvae, and eggs) of Tribolium confusum Jacquelin du Val (Coleoptera:Tenebrionidae), the confused flour beetle, and Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), the saw-toothed grain beetle (adults, larvae, and eggs) to 0, −5, −10, and −15°C. Larvae and pupae of T. confusum were more cold-tolerant than eggs or adults. Exposure to temperatures of −10°C for 1 d will kill nearly 100% of all life stages of T. confusum. O. surinamensis was more cold-tolerant than T. confusum. Adults of O. surinamensis were not killed when exposed for 1 d at −5°C, but egg hatch was drastically reduced after 2 h of exposure at the same temperature. Eggs and adults of O. surinamensis were more cold-tolerant than larvae. Our study indicates that target insect species and life stage, temperature, and exposure interval should all be considered when cold treatment is selected as a control strategy against T. confusum and O. surinamensis. Facility managers can use these data in planning cold treatments. © The Author(s) 2018

Efficacy of phosphine fumigation for different life stages of Trogoderma inclusum and Dermestes maculatus (Coleoptera: Dermestidae)

Despite the importance of dermestid beetles as targets for stored product protection, including the protection of museum artifacts and animal-based products, there are only a few published reports regarding their susceptibility to phosphine fumigation, in contrast with other major stored product insect species. In the current study, we evaluated phosphine against all life stages of Trogoderma inclusum LeConte, the larger cabinet beetle, and Dermestes maculatus (DeGeer), the hide beetle. There were two series of laboratory bioassays; in the first series the concentrations were 0 (control), 50, 100, 200 and 600 ppm, and in the second series the concentrations were 0 (control), 50, 150, 300, 400, 500 and 600 ppm. Both series were carried out on a 5-day insect exposure protocol. The results for both species clearly indicated that eggs were by far the least susceptible life stage, followed by pupae, while most adults and larvae were killed at the 50-ppm concentration. Concentrations between 300 and 400 ppm could be utilized to provide 100% mortality for both species and all life stages. To our knowledge, our results are the first that have provided data regarding efficacy of phosphine for the control of T. inclusum and D. maculatus. Resource managers can utilize our results to more efficiently target these dermestids with specific concentrations of phosphine, depending on the target life stage. © 2019 Elsevier Lt

Prophenoloxidase from Pieris rapae: gene cloning, activity, and transcription in response to venom/calyx fluid from the endoparasitoid wasp Cotesia glomerata *

Prophenoloxidase (PPO) plays an important role in melanization, necessary for defense against intruding parasitoids. Parasitoids have evolved to inject maternal virulence factors into the host hemocoel to suppress hemolymph melanization for the successful development of their progeny. In this study, the full-length complementary DNA (cDNA) of a Pieris rapae PPO was cloned. Its cDNA contained a 2 076-base pair (bp) open reading frame (ORF) encoding 691 amino acids (aa). Two putative copper-binding sites, a proteolytic activation site, three conserved hemocyanin domains, and a thiol ester motif were found in the deduced amino acid sequence. According to both multiple alignment and phylogenetic analysis, P. rapae PPO gene cloned here is a member of the lepidopteran PPO-2 family. Injection of Cotesia glomerata venom or calyx fluid resulted in reduction of P. rapae hemolymph phenoloxidase activity, demonstrating the ability to inhibit the host′s melanization. Real-time reverse transcriptase polymerase chain reaction (RT-PCR) showed that transcripts of P. rapae PPO-2 in the haemocytes from larvae had not significantly changed following venom injection, suggesting that the regulation of PPO messenger RNA (mRNA) expression by venom was not employed by C. glomerata to cause failure of melanization in parasitized host. While decreased P. rapae PPO-2 gene expression was observed in the haemocytes after calyx fluid injection, no detectable transcriptional change was induced by parasitization, indicating that transcriptional down-regulation of PPO by calyx fluid might play a minor role involved in inhibiting the host′s melanization