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Frank H Arthur - One of the best experts on this subject based on the ideXlab platform.
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Susceptibility of stored grain insects to the insect growth regulator Methoprene
Julius-Kühn-Archiv, 2018Co-Authors: Frank H ArthurAbstract:The insect growth regulator (IGR) Methoprene is labeled in the United States (US) for direct application to stored grain commodities, and as a residual surface treatment to empty grain bins and flooring surfaces inside indoor structures. Methoprene is also labeled in the US as an aerosol for use in indoor areas. One of the challenges in research with Methoprene and stored product insects is through design of experiments that mimic how Methoprene would be used in practical applications. Recent research with Methoprene will be used to describe experimental designs to examine efficacy of Methoprene when used as a grain protectant.
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Methoprene and control of stored-product insects
Journal of Stored Products Research, 2018Co-Authors: L.k.w. Wijayaratne, Frank H Arthur, S. WhyardAbstract:Abstract Estimated direct and indirect losses of grains and grain-based products caused by stored-product insects range from about 10% in temperate regions to almost 50% in humid tropical areas. Pest management strategies in bulk grains include the use of fumigants such as phosphine and sulfuryl fluoride, and grain protectants, which are sprayed directly on commodities as they are loaded into storage. Fumigants, aerosols, and contact sprays are also used as structural treatments in mills, processing plants, and food warehouses. Some older organophosphate protectants and contact sprays have been phased out worldwide and have been replaced by safer insecticides, including pyrethroids and insect growth regulators (IGRs). These IGRs include juvenile hormone analogues (JHAs), ecdysteroids and chitin synthesis inhibitors, and are considered safe due to their insect specificity. Methoprene is the JHA that has been used most extensively in stored-product pest management. The formulations of Methoprene originally introduced into the stored-product market in the 1980s contained the racemic mixture with both R- and S- forms, but now only the purified S-Methoprene isomer is used. Methoprene has received broad attention and has been tested over decades for its direct lethal effects, but many recent studies focus more on sub-lethal effects. Although Methoprene has been used for more than four decades, there has not been a recent and comprehensive synopsis or review of this IGR on stored-product insects. This review addresses the history and present use of Methoprene with special emphasis on stored-product protection.
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methodology for evaluating the insect growth regulator igr Methoprene on packaging films
Insects, 2016Co-Authors: Frank H ArthurAbstract:The insect growth regulator Methoprene can be mixed into the matrix used to comprise bags and other packaging materials. Different methodologies were utilized to evaluate the efficacy of different types of Methoprene-treated packaging towards Tribolium castaneum (Herbst), the red flour beetle, and T. confusum Jacquelin duVal, the confused flour beetle, two common insect species that infest stored products. Tests were conducted by creating arenas in which larvae were exposed on the packaging surface along with a flour food source, and assessments were made on adults emerging from the exposed progeny. Tests were also done by exposing adults, again with a flour food source, removing the adults after one week, and assessing adult emergence of progeny from those parental adults. In tests with larvae exposed on Methoprene-treated birdseed bags, the outside surface had more activity compared to the inside surface, especially on T. confusum. In other studies with different types of packaging materials, there was generally 100% inhibition of adult emergence of exposed larvae or of progeny adults when parental adults were exposed on the Methoprene-treated packaging. The best technique for evaluation was to expose late-stage larvae as the test life stage. Results show the potential of using Methoprene-treated packaging for bagged storage of processed grains and grain products.
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Mechanisms for horizontal transfer of Methoprene from treated to untreated Tribolium castaneum (Herbst)
Journal of Stored Products Research, 2014Co-Authors: Angela M. Tucker, Frank H Arthur, James F. Campbell, Kun Yan ZhuAbstract:Abstract Experiments were performed to determine the relative impact of different mechanisms of Methoprene horizontal transfer between Tribolium castaneum (Herbst) individuals. Larvae provided during later development with only dead Methoprene-treated developmental stages (late-stage larvae, pupae, or adults) resulted in no survival to adulthood. This suggests that transfer through cuticle contact could be involved, but some cannibalization also occurred. The average level of cannibalization was not different between Methoprene and control treatments, but the distribution of the amount of feeding did appear to be shifted to greater consumption by larvae exposed to Methoprene-treated individuals compared to water-treated. The potential impact of cannibalism on horizontal transfer was further evaluated by scoring the level of feeding by untreated larvae on either water or Methoprene-treated pupa and then comparing larval development and survival after different levels of cannibalization. In this experiment, the level of feeding on Methoprene-treated individuals did not affect the percentage of normal surviving adults (insects which emerged as adults, exhibited no external morphological malformations, and were alive at the end of the observational period), suggesting that consumption of treated individuals was not contributing significantly to horizontal transfer. Short-term confinement of a Methoprene or water treated adult with an untreated late-stage larva did not effect larval development and survival compared to the controls, indicating that brief contact between individuals was not sufficient for detectable negative effects. Transfer of Methoprene from treated individuals to a flour substrate and then to an untreated individual through contact with and/or feeding on the flour was evaluated. Exposure of larvae to Methoprene-contaminated flour during development resulted in a significantly lower number of normal surviving adults compared to controls. These results suggest that horizontal transfer of Methoprene is probably due to prolonged contact with Methoprene-treated individuals or Methoprene-contaminated flour.
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Horizontal transfer of Methoprene by Tribolium castaneum (Herbst) and Tribolium confusum Jacquelin du Val
Journal of Stored Products Research, 2014Co-Authors: Angela M. Tucker, Frank H Arthur, James F. Campbell, Kun Yan ZhuAbstract:Abstract In food facilities the majority of insect populations typically occur within hidden locations with limited direct exposure to insecticides, but there is potential for dispersing insects to transport insecticides into hidden areas and transfer insecticide to other individuals (i.e., horizontal transfer). In a series of laboratory experiments, the potential for transfer of the insect growth regulator Methoprene between treated and untreated Tribolium castaneum (Herbst) and Tribolium confusum (Jacquelin du Val) individuals was evaluated. In the first experiment, late-instar larvae were exposed to Methoprene or water treated individuals in flour and their ability to develop successfully was determined. For T. castaneum , survival time for individuals exposed to Methoprene treated individuals was shorter than those exposed to control individuals, but the difference was not significant for T. confusum . For both T. castaneum and T. confusum , the number of individuals that were able to successfully survive exposure and complete development without externally visible deformities was significantly reduced for individuals exposed to Methoprene treated pupae or larvae relative to controls, but not when exposed to Methoprene treated adults. In the second experiment, early-stage larvae, late-stage larvae, and pupae were similar in susceptibility to horizontal transfer of Methoprene, even though they were exposed as immatures for different lengths of time. In a third experiment, the potential for sublethal effects due to horizontal transfer of Methoprene was evaluated, but no difference in reproduction and oviposition was found for normal appearing adults that developed when exposed to Methoprene treated or and control individuals. This is the first report indicating that Methoprene can be transferred between stored-product insects and further research is needed to determine the impact this potentially has on pest populations.
Phillip W. Taylor - One of the best experts on this subject based on the ideXlab platform.
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Dietary Methoprene enhances sexual competitiveness of sterile male Queensland fruit flies in field cages
Journal of Pest Science, 2019Co-Authors: Saleh Mohammad Adnan, Iffat Farhana, Jess R. Inskeep, Polychronis Rempoulakis, Phillip W. TaylorAbstract:Queensland fruit flies Bactrocera tryoni (Froggatt) have a long adult maturation phase which, together with high mortality rates, can substantially reduce number of released flies that survive to mature and contribute to sterile insect technique (SIT) programmes. This constraint on SIT can potentially be addressed by incorporating Methoprene, a juvenile hormone analogue, into an adult diet of sugar and yeast hydrolysate for 2 days after emergence. Methoprene treatments have been found to accelerate sexual development of male Queensland fruit fly, resulting in increased mating propensity of 5–7-day-old males in no-choice laboratory trials. Before considering deployment of Methoprene as a pre-release treatment in SIT, it is necessary to demonstrate mating competitiveness and compatibility of Methoprene-treated flies under field-like conditions. In the present study, we assessed whether Methoprene treatment increases ability of sterile males (5 and 7 days old) to compete with mature (wild or laboratory) males for matings with mature (wild or laboratory) females in field cages. We also investigated mating compatibility to test for sexual isolation between sterile flies and mature (wild or laboratory) fertile flies. In mating competitiveness tests, Methoprene-treated males of either age outperformed mature wild or laboratory males for matings with mature wild or laboratory females, respectively. Untreated 5- and 7-day-old males were less competitive than mature wild or laboratory mature males and hence had lower relative sterility indexes. Methoprene-treated males mated earlier in the evening and continued mating for longer than untreated sterile males and mature wild or laboratory males. In mating compatibility trials, Methoprene-treated males mated equally with Methoprene-treated females and mature females, whereas Methoprene-treated females tended to mate more often with mature males than with Methoprene-treated males. However, untreated flies of both sexes exhibited substantial sexual isolation. Pairings that comprised Methoprene-treated males and mature females had shorter mating latency and longer copulations than other pairings. Unlike males, Methoprene-treated females did not exhibit changes in mating latency or duration. Overall, the present study supports the use of pre-release dietary Methoprene treatment in Queensland fruit fly SIT.
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Accelerated Sexual Maturation in Methoprene-Treated Sterile and Fertile Male Queensland Fruit Flies (Diptera: Tephritidae), and Mosquito Larvicide as an Economical and Effective Source of Methoprene.
Journal of Economic Entomology, 2019Co-Authors: Saleh Mohammad Adnan, Iffat Farhana, Jess R. Inskeep, Polychronis Rempoulakis, Phillip W. TaylorAbstract:Queensland fruit flies Bactrocera tryoni ('Q-fly') have long adult prereproductive development periods, which can present challenges for sterile insect technique (SIT) programs. Holding the sterile flies in release facilities is expensive for control programs. Alternatively, releases of sexually immature males can lead to substantial mortality of sterile males before they mature. Recent studies have reported effectiveness of dietary supplementation with a mosquito larvicide (NOMOZ) that contains S-Methoprene, a juvenile hormone analogue, for accelerating sexual development of fertile Q-fly males. However, it is not known whether effects on sterile flies are comparable to effects on fertile flies, or whether effects of Methoprene-containing larvicide are comparable to effects of analytical standard Methoprene such has been used in most studies. Here we address both knowledge gaps, investigating the effects of analytical standard Methoprene and NOMOZ mixed with food and provided for 48 h following emergence on sexual development and longevity of fertile and sterile Q-flies. Compared with controls, fertile and sterile male Q-flies that were provided diets supplemented with Methoprene from either source exhibited substantially accelerated sexual development by 2-3 d and longer mating duration. Unlike males, females did not respond to Methoprene treatment. Although fertile and sterile flies were generally similar in sexual development and response to Methoprene treatment, sterile flies of both sexes tended to have shorter copula duration than fertile flies. Neither Methoprene supplements nor sterilization affected longevity of flies. The present study confirms effectiveness of dietary Methoprene supplements in accelerating sexual development of both fertile and sterile male (but not female) Q-flies, and also confirms that low-cost mosquito larvicides that contain Methoprene can achieve effects similar to those for high-cost analytical grade Methoprene as prerelease supplements for Q-fly SIT.
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Dietary Methoprene supplement promotes early sexual maturation of male Queensland fruit fly Bactrocera tryoni
Journal of Pest Science, 2018Co-Authors: Saleh Mohammad Adnan, Iffat Farhana, Vivian Mendez, Renata Morelli, Humayra Akter, Phillip W. TaylorAbstract:Sterile insect technique (SIT) is an environmentally benign pest management technique that relies on released sterile male insects mating with, and curtailing reproduction of, wild females. However, for species with high mortality rates and long adult maturation phases, a large proportion of the released insects can die before maturing and so fail to contribute to SIT. To counter this problem, inclusion of yeast hydrolysate in pre-release diets and treatment of pupae or adults with Methoprene, a juvenile hormone analogue, have been investigated as means of accelerating development of some fruit flies, including Queensland fruit fly, Bactrocera tryoni (Froggatt) (‘Q-fly’). Methoprene has most often been administered topically in acetone solution, which is toxic, flammable, and impractical for operational settings. As a practical alternative, we incorporated Methoprene (0, 0.05, 0.1, and 0.5%) into Q-fly adult diet of sugar only or sugar mixed with yeast hydrolysate for 2 days, and then provided sugar only for the rest of the trial period. Mating performance of males and females was tested from 4 to 30 days of age. Flies provided sugar mixed with yeast hydrolysate had increased mating propensity in comparison with flies that were provided sugar only. At all ages and for both diets, all Methoprene doses increased male mating probability. Methoprene treatment did not affect copula latency of males that received yeast hydrolysate, but males that received only sugar mated earlier if they had received 0.05% Methoprene. Methoprene treatment of males was also associated with longer copulations, which may affect fertility of females that later remate. Females differed from males in that Methoprene treatment did not significantly affect mating probability or latency, but resembled males in that Methoprene treatment resulted in longer copulations. Sex differences in response to Methoprene may lead to male-biased operational sex ratio when bisex Q-fly strains are used in SIT. Yeast hydrolysate increased longevity of both males and females, but Methoprene treatment did not affect longevity. Overall, findings of the present study indicate that Q-fly sexual maturation can be accelerated, and SIT might hence be enhanced, by incorporation of Methoprene and yeast hydrolysate in pre-release diet.
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combined effects of dietary yeast supplementation and Methoprene treatment on sexual maturation of queensland fruit fly
Journal of Insect Physiology, 2014Co-Authors: S R Collins, Olivia L Reynolds, Phillip W. TaylorAbstract:Yeast hydrolysate supplements promote maturation of many tephritid flies targeted for control using the sterile insect technique (SIT), including Queensland fruit fly (Bactrocera tryoni; 'Q-fly'). Recently, application of the juvenile hormone analogue Methoprene has been demonstrated to further promote maturation in some species. We here investigate the separate and combined effects of yeast hydrolysate and Methoprene treatment on sexual maturation of sterile male and female Q-flies. Two methods of applying Methoprene solution were used; topical application to adults and dipping of pupae. Consistent with previous studies, access to yeast hydrolysate greatly increased maturation of both male and female Q-flies. Maturation was further promoted by Methoprene treatment, with similar effects evident for males and females and for both application methods. For flies provided access to yeast hydrolysate supplements, Methoprene treatment advanced maturation by approximately 2days. No effects of diet or Methoprene treatment were found on timing of copulation or copula duration. Countering the positive effects on sexual maturation, dipping of pupae in Methoprene/acetone solution did diminish emergence rates and flight ability indices, and increased rates of wing deformity. Promising results of the present study encourage further investigation of treatment methods that maximise maturation while minimising detrimental effects on other aspects of fly quality.
Paul G. Fields - One of the best experts on this subject based on the ideXlab platform.
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residual efficacy of Methoprene for control of tribolium castaneum coleoptera tenebrionidae larvae at different temperatures on varnished wood concrete and wheat
Journal of Economic Entomology, 2012Co-Authors: L Wolly K Wijayaratne, Paul G. Fields, Frank H ArthurAbstract:The residual efficacy of the juvenile hormone analog Methoprene (Diacon II) was evaluated in bioassays using larvae of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) exposed on unsealed concrete or varnished wood treated with a liquid formulation and held at different temperatures. When these two types of surfaces were stored at 20, 30 or 35°C for 0–24 wk, the percentage of adult emergence on concrete increased with time. In contrast, there was no adult emergence from larvae exposed to varnished wood at 24 wk after treatment at any of these temperatures. The presence of flour reduced residual efficacy of Methoprene on concrete, but not on varnished wood, with no differences between cleaning frequencies. Methoprene was also stable for 48 h on concrete held at 65°C and wheat, Triticum aestivum L., held at 46°C. Results show that Methoprene is stable at a range of temperatures commonly encountered in indoor food storage facilities and at high temperatures attained during insecticidal heat treatments of structures. The residual persistence of Methoprene applied to different surface substrates may be affected more by the substrate than by temperature.
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Effect of Methoprene on the progeny production of Tribolium castaneum (Coleoptera: Tenebrionidae)
Pest Management Science, 2011Co-Authors: Leanage K. W. Wijayaratne, Paul G. Fields, Frank H ArthurAbstract:BACKGROUND: Tribolium castaneum (red flour beetle) is a serious insect pest of stored products around the world. Current control measures for this species have several limitations: loss of registration of insecticides, insecticide resistance and consumer concerns about chemical residues in food. The objective of this study was to determine whether Methoprene affects progeny production of T. castaneum. Late-instar larvae or young adults were exposed to Methoprene-treated wheat, and progeny production was determined. The pairing of male and female adults was performed as untreated × untreated, treated × untreated or treated × treated, to study sex-based effects. RESULTS: There were three outcomes to late-instar larvae held on Methoprene-treated wheat kernels (0.001 and 0.0165 ppm): (1) failure to emerge as an adult; (2) emergence as an adult, and almost no offspring produced; (3) emergence as an adult and normal production of offspring. Male larvae were more susceptible to Methoprene than female larvae. In contrast, young adults exposed to Methoprene (1.67 – 66.6 ppm) showed no reduction in offspring production. CONCLUSION: Methoprene concentrations will decline with time following its application. However, this research indicates that Methoprene can still reduce populations of T.castaneum by reducing their progeny production, even if adults emerge. c � 2011 Society of Chemical Industry
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Effects of Methoprene on extreme temperature tolerance and reproduction of Tribolium castaneum (Coleoptera: Tenebrionidae)
Julius-Kühn-Archiv, 2010Co-Authors: Leanage K. W. Wijayaratne, Paul G. FieldsAbstract:The juvenile hormone analogue Methoprene is a reduced-risk insecticide. It disrupts insect development of immature stages preventing the emergence of adults. Several studies have shown that lower concentrations that permit the emergence of adults also have sub-lethal effects. Exposure to Methoprene (Diacon II) at 3.33 ppm reduced the heat tolerance of Tribolium castaneum (Herbst) adults. However, it did not affect the heat tolerance of larvae at 0.07 ppm. Higher concentrations of Methoprene were lethal to larvae without heat treatment. Methoprene (67 ppm) had no effect on the cold tolerance of adults. Furthermore, Methoprene (0.03 ppm) did not alter cold tolerance of larvae. Exposure to 15°C for 2 weeks increased the cold tolerance of adults from 4 d to 7 d, and larvae 3 d to 5 d; however, Methoprene concentrations had no effect on cold tolerance. Tribolium castaneum larvae exposed to Methoprene (0.001 ppm) had lower fecundity as adults. Males were more affected than females in reducing the offspring when paired with untreated mates. These results show the potential of Methoprene as an emerging insecticide and a viable alternative to currently used synthetic insecticides. The data on the effect of Methoprene on extreme temperature tolerance of T. castaneum have been submitted to the Journal of Stored Products Research. Keywords : Methoprene, Extreme temperature tolerance, Reproduction, Larvae, Adults
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Effect of Methoprene on the heat tolerance and cold tolerance of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)
Journal of Stored Products Research, 2010Co-Authors: Leanage K. W. Wijayaratne, Paul G. FieldsAbstract:Abstract Methoprene, a Juvenile Hormone analogue, was evaluated for its ability to alter heat tolerance or cold tolerance of Tribolium castaneum , the red flour beetle. Young adults and late instar larvae were exposed to a series of Methoprene concentrations. They were held either at 46 °C or 0 °C for different durations, and survival of adults or the adult emergence from larvae was recorded to determine their tolerance to extreme temperatures. At 46 °C, the lethal time to kill 50% of the population (confidence intervals) for untreated adults was 10.8 (9.6–11.8) h compared to 9.3 (8.3–10.0) h for adults exposed to 3.33 ppm of Methoprene for 48 h. Higher concentrations of Methoprene also caused adults to be less heat tolerant. In contrast, there was no evidence that Methoprene reduced the heat tolerance of larvae. At 0 °C, both unacclimated and cold-acclimated insects were tested. Methoprene did not affect the cold tolerance of adults or larvae, regardless of cold acclimation. As seen in other studies, Methoprene was not toxic to adults even at 66.6 ppm, but it was highly toxic to larvae (LD 50 0.015 to 0.020 ppm). Cold tolerance was slightly greater in both adults and larvae, after being held at 15 °C for two weeks. This is the first study to report that a Juvenile Hormone analogue has an impact on insect heat tolerance.
Jorge Hendrichs - One of the best experts on this subject based on the ideXlab platform.
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precocious sexual signalling and mating in anastrepha fraterculus diptera tephritidae sterile males achieved through juvenile hormone treatment and protein supplements
Bulletin of Entomological Research, 2013Co-Authors: M C Liendo, M E Utges, Francisco Devescovi, M. T. Vera, Guillermo E Bachmann, Solana Abraham, Silvia Beatriz Lanzavecchia, Juan P R Bouvet, P Gomezcendra, Jorge HendrichsAbstract:Sexual maturation of Anastrepha fraterculus is a long process. Methoprene (a mimic of juvenile hormone) considerably reduces the time for sexual maturation in males. However, in other Anastrepha species, this effect depends on protein intake at the adult stage. Here, we evaluated the mating competitiveness of sterile laboratory males and females that were treated with Methoprene (either the pupal or adult stage) and were kept under different regimes of adult food, which varied in the protein source and the sugar:protein ratio. Experiments were carried out under semi-natural conditions, where laboratory flies competed over copulations with sexually mature wild flies. Sterile, Methoprene-treated males that reached sexual maturity earlier (six days old), displayed the same lekking behaviour, attractiveness to females and mating competitiveness as mature wild males. This effect depended on protein intake. Diets containing sugar and hydrolyzed yeast allowed sterile males to compete with wild males (even at a low concentration of protein), while brewer´s yeast failed to do so even at a higher concentration. Sugar only fed males were unable to achieve significant numbers of copulations. Methoprene did not increase the readiness to mate of six-day-old sterile females. Long pre-copulatory periods create an additional cost to the management of fruit fly pests through the sterile insect technique (SIT). Our findings suggest that Methoprene treatment will increase SIT effectiveness against A. fraterculus when coupled with a diet fortified with protein. Additionally, Methoprene acts as a physiological sexing method, allowing the release of mature males and immature females and hence increasing SIT efficiency.
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effects of the juvenile hormone analogue Methoprene and dietary protein on male melon fly bactrocera cucurbitae diptera tephritidae mating success
Journal of Insect Physiology, 2010Co-Authors: Ihsan Ul Haq, Peter E A Teal, Carlos Caceres, Jorge Hendrichs, Viwat Wornoayporn, Christian Stauffer, Alan S RobinsonAbstract:Abstract The effect of access to dietary protein (P) and the topical application of a juvenile hormone analogue (Methoprene (M)) on mating behaviour of male melon fly Bactrocera cucurbitae was assessed in the laboratory and in field cages. Age, dietary protein and Methoprene application increased the mating success and influenced the mating behaviour. Treatment with Methoprene (M+) to protein-deprived (P−) males had only a modest effect on the acceleration of sexual maturity, but application of Methoprene (M+) to protein-fed (P+) males greatly accelerated sexual maturity. Protein diet (P+) increased mating success of males in comparison to protein-deprived (P−) males. Protein and Methoprene have a synergistic effect on mating behaviour, since M + P+ treated males exhibit reduced mating latency and achieved higher mating in younger ages than Methoprene and/or protein-deprived males. Copulation duration was correlated with nutritional status and M + P+ males copulated longer at the age of advanced sexual maturity than M − P+ males. Our results suggest that in this species with a lek mating system, females discriminate between the males based on their sexual signals, which were influenced by protein in the adult diet, Methoprene application and age. The results are discussed in the light of mating competitiveness of precocious treated young males and their relevance to Sterile Insect Technique application against this pest species.
Leanage K. W. Wijayaratne - One of the best experts on this subject based on the ideXlab platform.
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Effect of Methoprene on the progeny production of Tribolium castaneum (Coleoptera: Tenebrionidae)
Pest Management Science, 2011Co-Authors: Leanage K. W. Wijayaratne, Paul G. Fields, Frank H ArthurAbstract:BACKGROUND: Tribolium castaneum (red flour beetle) is a serious insect pest of stored products around the world. Current control measures for this species have several limitations: loss of registration of insecticides, insecticide resistance and consumer concerns about chemical residues in food. The objective of this study was to determine whether Methoprene affects progeny production of T. castaneum. Late-instar larvae or young adults were exposed to Methoprene-treated wheat, and progeny production was determined. The pairing of male and female adults was performed as untreated × untreated, treated × untreated or treated × treated, to study sex-based effects. RESULTS: There were three outcomes to late-instar larvae held on Methoprene-treated wheat kernels (0.001 and 0.0165 ppm): (1) failure to emerge as an adult; (2) emergence as an adult, and almost no offspring produced; (3) emergence as an adult and normal production of offspring. Male larvae were more susceptible to Methoprene than female larvae. In contrast, young adults exposed to Methoprene (1.67 – 66.6 ppm) showed no reduction in offspring production. CONCLUSION: Methoprene concentrations will decline with time following its application. However, this research indicates that Methoprene can still reduce populations of T.castaneum by reducing their progeny production, even if adults emerge. c � 2011 Society of Chemical Industry
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Effects of Methoprene on extreme temperature tolerance and reproduction of Tribolium castaneum (Coleoptera: Tenebrionidae)
Julius-Kühn-Archiv, 2010Co-Authors: Leanage K. W. Wijayaratne, Paul G. FieldsAbstract:The juvenile hormone analogue Methoprene is a reduced-risk insecticide. It disrupts insect development of immature stages preventing the emergence of adults. Several studies have shown that lower concentrations that permit the emergence of adults also have sub-lethal effects. Exposure to Methoprene (Diacon II) at 3.33 ppm reduced the heat tolerance of Tribolium castaneum (Herbst) adults. However, it did not affect the heat tolerance of larvae at 0.07 ppm. Higher concentrations of Methoprene were lethal to larvae without heat treatment. Methoprene (67 ppm) had no effect on the cold tolerance of adults. Furthermore, Methoprene (0.03 ppm) did not alter cold tolerance of larvae. Exposure to 15°C for 2 weeks increased the cold tolerance of adults from 4 d to 7 d, and larvae 3 d to 5 d; however, Methoprene concentrations had no effect on cold tolerance. Tribolium castaneum larvae exposed to Methoprene (0.001 ppm) had lower fecundity as adults. Males were more affected than females in reducing the offspring when paired with untreated mates. These results show the potential of Methoprene as an emerging insecticide and a viable alternative to currently used synthetic insecticides. The data on the effect of Methoprene on extreme temperature tolerance of T. castaneum have been submitted to the Journal of Stored Products Research. Keywords : Methoprene, Extreme temperature tolerance, Reproduction, Larvae, Adults
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Effect of Methoprene on the heat tolerance and cold tolerance of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)
Journal of Stored Products Research, 2010Co-Authors: Leanage K. W. Wijayaratne, Paul G. FieldsAbstract:Abstract Methoprene, a Juvenile Hormone analogue, was evaluated for its ability to alter heat tolerance or cold tolerance of Tribolium castaneum , the red flour beetle. Young adults and late instar larvae were exposed to a series of Methoprene concentrations. They were held either at 46 °C or 0 °C for different durations, and survival of adults or the adult emergence from larvae was recorded to determine their tolerance to extreme temperatures. At 46 °C, the lethal time to kill 50% of the population (confidence intervals) for untreated adults was 10.8 (9.6–11.8) h compared to 9.3 (8.3–10.0) h for adults exposed to 3.33 ppm of Methoprene for 48 h. Higher concentrations of Methoprene also caused adults to be less heat tolerant. In contrast, there was no evidence that Methoprene reduced the heat tolerance of larvae. At 0 °C, both unacclimated and cold-acclimated insects were tested. Methoprene did not affect the cold tolerance of adults or larvae, regardless of cold acclimation. As seen in other studies, Methoprene was not toxic to adults even at 66.6 ppm, but it was highly toxic to larvae (LD 50 0.015 to 0.020 ppm). Cold tolerance was slightly greater in both adults and larvae, after being held at 15 °C for two weeks. This is the first study to report that a Juvenile Hormone analogue has an impact on insect heat tolerance.
