Thermal death kinetics of fifth-instar Plodia interpunctella (Lepidoptera: Pyralidae)

Heat treatments have been suggested as alternatives to chemical fumigants for control of postharvest insects in dried fruits and nuts. Conventional forced hot air treatments heat product too slowly to be practical, but radio frequency treatments are capable of more rapid product heating. While developing radio frequency heat treatments for dried fruits and nuts, the heat tolerance of nondiapausing and diapausing fifth-instar larvae of the Indianmeal moth, Plodia interpunctella (Hübner), was determined using a heating block system developed by Washington State University. Both a 0.5th order kinetic model and a classical empirical model were used to estimate lethal exposure times for temperatures of 44-52 degrees C for nondiapausing fifth-instar larvae. We obtained 95% mortality at exposures suitable for practical radio frequency treatments (< or = 5 min) with temperatures of 50 and 52 degrees C. Diapausing larvae were significantly more tolerant than nondiapausing larvae at the lowest treatment temperature and shortest exposure, but differences were not significant at more extreme temperature-time combinations. Previous studies showed that fifth-instar larvae of the navel orangeworm, Amyelois transitella (Walker), were more heat tolerant than either diapausing or nondiapausing Indianmeal moth larvae. Consequently, efficacious treatments for navel orangeworm would also control Indianmeal moth.     

Activity of Plodia interpunctella (Lepidoptera: Pyralidae) in and around flour mills

Studies were conducted at two flour mills where male Indian meal moths, Plodia interpunctella (Hübner), were captured using pheromone-baited traps. Objectives were to determine the distribution of male P. interpunctella at different locations in and around the mills throughout the season, and to monitor moth activity before and after one of the mills was fumigated with methyl bromide to assess efficacy of treatment. Commercially available sticky traps baited with the P. interpunctella sex pheromone were placed at various locations outside and within the larger of the two mills (mill 1). Moths were captured inside mill 1 after methyl bromide fumigations. The highest numbers of P. interpunctella were caught outside the facility and at ground floor locations near outside openings. Additional traps placed in the rooms above the concrete stored-wheat silos at mill 1 during the second year captured more moths than did traps within the mill's production and warehouse areas. In another study, moths were trapped at various distances from a smaller flour mill (mill 2) to determine the distribution of moths outdoors relative to the mill. There was a negative correlation between moth capture and distance from the facility, which suggested that moth activity was concentrated at or near the flour mill. The effectiveness of the methyl bromide fumigations in suppressing moth populations could not be assessed with certainty because moths captured after fumigation may have immigrated from outside through opened loading bay warehouse doors. This study documents high levels of P. interpunctella outdoors relative to those recorded inside a food processing facility. Potential for immigration of P. interpunctella into flour mills and other stored product facilities from other sources may be greater than previously recognized. Moth entry into a food processing facility after fumigation is a problem that should be addressed by pest managers.     

Attractancy and toxicity of an attracticide for Indianmeal moth, Plodia interpunctella (Lepidoptera: Pyralidae)

Plodia interpunctella (Hübner) is a serious and widespread postharvest pest on cereal products, dried fruits, candy, and pet food. Due to the strong positive anemotactic flight response of P. interpunctella males to the main component of the female-produced pheromone [(Z,E)-9,12-tetradecadienyl acetate, herein referred to as ZETA], we evaluated the potential of an attracticide for this pest, in which ZETA as attractant was combined with permethrin as the killing agent. Two concentrations of ZETA [0.16 and 0.32% (wt:wt)] and five concentrations of permethrin [0, 3, 6, 12, and 18% (wt:wt)] were incorporated into Last Call gel (10 different permethrin:ZETA combinations). All attracticide gels were evaluated in a toxicity test, in which either the tip of a leg or an antenna of a virgin P. interpunctella male was touched < 3 s into a dot of attracticide gel. These males were subsequently transferred to jars with virgin females. The toxicity test showed that a brief and gentle contact of P. interpunctella males with attracticide gel containing 3-18% permethrin caused a significant reduction in mating and killed males moths within 24 h. A wind tunnel test was conducted to evaluate the flight responses of P. interpunctella males to the same 10 attracticide gels. Male moths displayed significantly higher levels of positive anemotactic flight and more males made contact with the attracticide gel when the ZETA concentration was 0.16% compared with 0.32%. P. interpunctella males showed no signs of repellency to permethrin concentrations within a range of 0-18% in the attracticide gel. Three densities of P. interpunctella pairs were released into small warehouse rooms, and we found that the attracticide gel suppressed oviposition when the moth density was at a low level, but it was ineffective when the moth density exceeded one male-female pair per 11.3 m3.     

Effects of transgenic Bacillus thuringiensis maize grain on B. thuringiensis-susceptible Plodia interpunctella (Lepidoptera: Pyralidae)

Percentage survivorship, developmental time, adult body length, and sex ratio of Plodia interpunctella (Hübner) reared on field-produced grain from sixteen cultivars of maize, Zea mays L., including several transgenic Bacillus thuringiensis (Bt) Berliner hybrids and selected non-Bt isolines, were evaluated under laboratory conditions. Compared with isolines, development was delayed and survivorship reduced for P. interpunctella reared on grain from transgenic hybrids with the CaMV/35s promoter that express Cry1Ab protein. Similarly, compared with non-Bt hybrids, a transgenic hybrid with the CaMV/35s promoter that expresses Cry9C protein delayed development, decreased survivorship, and caused reductions in adult body length of P. interpunctella. In contrast, no significant differences in P. interpunctella developmental times or survivorship were observed between transgenic hybrids with the PEPC promoter expressing Cry1Ab and their isolines. Additionally, developmental time, survivorship, and adult body length were similar between P. interpunctella reared on a transgenic hybrid with the CaMV/35s promoter expressing Cry1Ac and non-Bt hybrids. Our data demonstrate that transgenic Bt maize grain, especially grain from hybrids with the CaMV/35s promoter expressing Cry1Ab or Cry9C, can significantly affect B. thuringiensis-susceptible P. interpunctella populations up to 4 or 5 mo after harvest.     

Susceptibility of Plodia interpunctella (Lepidoptera: Pyralidae) developmental stages to high temperatures used during structural heat treatments

Heating the ambient air of a whole, or a portion of a food-processing facility to 50 to 60 degrees C and maintaining these elevated temperatures for 24 to 36 h, is an old technology, referred to as heat treatment. There is renewed interest in adopting heat treatments around the world as a viable insect control alternative to fumigation with methyl bromide. There is limited published information on responses of the Indian meal moth, Plodia interpunctella (Hübner), exposed to elevated temperatures typically used during heat treatments. Time-mortality relationships were determined for eggs, fifth-instars (wandering-phase larvae), pupae, and adults of P. interpunctella exposed to five constant temperatures between 44 and 52 degrees C. Mortality of each stage increased with increasing temperature and exposure time. In general, fifth-instars were the most heat-tolerant stage at all temperatures tested. Exposure for a minimum of 34 min at 50 degrees C was required to kill 99% of the fifth-instars. It is proposed that heat treatments aimed at controlling fifth-instars should be able to control all other stages of P. interpunctella.     

Comparative mortality of diapausing and nondiapausing larvae of Plodia interpunctella (Lepidoptera: Pyralidae) exposed to monoterpenoids and low pressure

Monoterpenoids and low pressure have each been demonstrated to cause mortality of stored-product insect pests. The current report investigated the prospects of integrating the two methods in the management of diapausing and nondiapausing larvae of Plodia interpunctella (Hübner). In a separate experiment, the larvae were exposed to 35.5 mmHg in Erlenmeyer flasks at 19 and 28 degrees C for times ranging from 30 min to 96 h. Another set of experiments was conducted to investigate the toxicity of exposing P. interpunctella larvae to monoterpenoids including E-anethole, estragole, S-carvone, linalool, L-fenchone, geraniol, gamma-terpinene, and DL-camphor alone or in combination with low pressure (50 mmHg). Lethal times (LT) determined by subjecting time-mortality data to probit analyses were shortened to half when both diapausing and nondiapausing larvae were exposed to low pressure at 28 degrees C compared with 19 degrees C. Exposure of diapausing larvae to a monoterpenoid alone, with the exception of DL-camphor and estragole, at a concentration of 66.7 microl/1L of volume required > 30 h to generate 99% mortality at 19.0 +/- 0.8 degrees C. However, the LT99 values for diapausing and nondiapausing larvae exposed to combinations of DL-camphor or estragole and low pressure were considerably shortened. Combinations involving the rest of the monoterpenoids investigated and low pressure did not generate LT99 that were shorter than those of the control, which was low pressure only. These results suggest that integrating low pressure with DL-camphor or estragole could be a new method for the control of diapausing larvae of P. interpunctella at cooler temperatures.     

Life tables of Habrobracon hebetor (Hymenoptera: Braconidae) parasitizing Anagasta kuehniella and Plodia interpunctella (Lepidoptera: Pyralidae): effect of host density

The reproductive performance of the parasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae) against the moths Anagasta kuehniella Zeller and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) was studied in the laboratory. The analysis was based on the comparison of parasitoid's life table parameters related to those of its hosts at various conditions of host density (daily supply of 1, 5, 15, and 30 full-grown host larvae). The estimated parameters were the intrinsic rate of natural increase (rm), the net reproductive rate (R0), the mean generation time (G), the finite capacity of increase (lambda), the gross reproductive rate (GRR), the doubling time (DT), the reproductive value (Vx), and the life expectancy (ex). The rm of H. hebetor proved to be significantly higher than those of its hosts at all host densities. When only one host per day was supplied, the wasp had the lowest reproductive potential, whereas it was maximized when 15 hosts per day were exposed. Maximum values of R0 and GRR were obtained at densities > or =15 host larvae per day. Any increase in host supply above this threshold did not cause significant changes in life table parameters. Variation of rm as a function of host density can be described by the linear regression. Sex ratio of wasp progeny (females/total) ranged from 0.36 to 0.42, irrespective of host density or species. Newly emerged adults recorded maximum ex and Vx. The results of this study can be used to improve mass rearing programs and inoculative release applications of H. hebetor against moth pests of stored products.     

Efficacy of an esfenvalerate plus methoprene aerosol for the control of eggs and fifth instars of Plodia interpunctella (Lepidoptera: Pyralidae)

Abstract  Aerosol insecticides may provide an alternative to fumigants for control of the Indianmeal moth, Plodia interpunctella (Hübner), the Indianmeal moth, a major insect pest of stored processed food. In this study, eggs and larvae (5th instars) of P . interpunctella were exposed to aerosol applications of the pyrethroid esfenvalerate and insect growth regulator methoprene, alone and in combination, in open and obstructed positions inside small sheds. When larvae were exposed to methoprene alone, adult emergence from those exposed larvae was 7.1%± 1.5%. In contrast, adult emergence was 92.5%± 3.5% when larvae were exposed to esfenvalerate alone. When eggs were exposed to methoprene, adult emergence of those exposed eggs was approximately 75%; however, when eggs were exposed to esfenvalerate, adult emergence was approximately 35%. In the combination treatment of methoprene plus esfenvalerate at their respective label rates, adult emergence following larval exposure was 0.91%± 0.61% compared to 16.3%± 9.6% when eggs were exposed. Based on our results, methoprene alone is highly effective in reducing adult emergence after larval exposure. However, it is not as effective on eggs as esfenvalerate. A combination treatment of esfenvalerate plus methoprene could be used to control eggs and the wandering-phase larval stages of P . interpunctella . An economic risk analysis also supports a strategy of combining methoprene and esfenvalerate.     

Effects of shelf architecture and parasitoid release height on biological control of Plodia interpunctella (Lepidoptera: Pyralidae) eggs by Trichogramma deion (Hymenoptera: Trichogrammatidae)

The effects of shelving type, packaging, and release height on success of Trichogramma deion Pinto & Oatman (Hymenoptera: Trichogrammatidae) parasitizing Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) eggs was studied under laboratory conditions. In trials on multipletiered gondola-type or open shelving units, with or without packaging, foraging success was evaluated by comparing parasitism and total mortality rates of sentinel egg disks among shelves after a single point-release of T. deion. Results showed that T. deion parasitized more egg disks and killed more total eggs on open shelves than on gondola shelving. The presence of packaging had no effect on parasitoid foraging on open shelves; however, packaging did interfere with parasitism of P. interpunctella eggs on gondola shelving. Egg parasitism and mortality patterns among shelves were not as evenly distributed on gondola-type shelving compared with open shelving. On gondola shelves without packages, changing the release point of T. deion from the middle to the lowest shelf shifted the distribution of parasitism toward the floor. Gondola shelving, especially in the presence of packaging, reduced foraging efficiency of T. deion for P. interpunctella eggs. Thus, to attain adequate control of P. interpunctella, it may be necessary to use two release heights on gondola shelving.     

Effet des rayons gamma sur les larves de Plodia interpunctella (Lepidoptera: Phycitidae)

Résumé On peut envisager de protéger les produits emmagasinés tels que pistaches, noix, amandes, noisettes décortiquées, contre les détériorations dûes aux pullulations des larves et adultes de Plodia interpunctella (Lépidopt. Phycitidae), en irradiant ces produits avec des doses appropriées de rayons gamma. Nos expériences montrent que des doses de 10 Krads appliquées à des larves du dernier stade, prolongent la durée de la vie nymphale, réduisent le pourcentage d'émergence des imagos et provoquent chez les femelles une régression des ovaires. Ces effets sont encore plus marqués avec des doses de 12 et 14 Krads. Cette dernière dose pourrait être la dose optimum à envisager.

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Summary Protection of stored products such as pistachio nuts, walnuts, almonds and shelled hazel nuts against damage from infestation by larvae and adults of Plodia interpunctella (Lepidoptera: Phycitidae) by radiating these products with appropriate doses of gamma rays, can now be considered. Our tests show that doses of 10 krad applied to last-stage larvae prolong the length of pupal life, reduce the percentage of imaginal emergence and cause regression of the female ovaries. These effects are even more pronounced with doses of 12 and 14 krad. This last dose may well deserve the most attention.

     

Factors governing the induction of diapause in Ephestia elutella and Plodia interpunctella (Lepidoptera)

Diapause in fully grown larvae of Ephestia elutella and Plodia inferpunctella was induced by low temperature and short photoperiods. Light intensities below 1 lx affected the induction of diapause in both species. At 20 and 25d?C, the critical photo-period for E.elutella was c. 14 h, and for P.interpunctella c. 13 h. The sensitive phase in both species occurred at about the time of the fourth larval moult. In E.elutella about seven short photoperiods were required for larvae to enter diapause. In P.interpunctella high population density during larval development increased the proportion of larvae entering diapause. The conditions inducing diapause in laboratory stocks, and in stocks collected from the field, were different. Laboratory stocks of both species did not enter diapause at 25d?C and required short photoperiods for diapause at 20d?C. Some larvae of the field stock of E.elutella entered diapause in constant darkness at 30d?C, the number being increased at low R.H., and almost all did in short photoperiods at 25°C. At 20T, most larvae of this stock entered diapause regardless of photoperiod, and at 15°C all did. In P.interpunctella up to one-third of larvae of the field stock entered diapause in short photoperiods at 25d?C, and all did if transferred to short photoperiods at 20d?C. In unheated premises, falling temperatures normally induce diapause in E.elutella each autumn, photoperiod only being important if temperatures are high. In P.interpunctella, photoperiod is a more important factor because it can override the effect of falling temperature to a greater extent than in E.elutella. In both species, however, different field populations may respond in different ways.     

Non-specific resistance in brown planthopper resistant indica rice varieties against Plodia interpunctella (Lepidoptera: Phycitidae)

Mechanisms of host plant resistance against insect pests can be manifold. Resistance screenings generally use single target insect pests, but the resistance thus screened may not always be specific to the target insect species. We conducted a test for non‐specific resistance in indica rice varieties with resistance genes against brown planthopper (BPH), by using the Indian meal moth, Plodia interpunctella. The test system was very simple, and only required the non‐pest moth to be reared on rice flour. We compared the survival rate, developmental period and adult weight of the moth on three rice varieties: ‘Nipponbare’, a BPH‐susceptible japonica variety, and ‘Thai Collection 11’ and ‘Pokkali’, two resistant indica varieties. Our results were straightforward and demonstrate that resistance in the two resistant rice varieties is not BPH specific, because development of the moth was retarded and adult body weight was reduced.     

Major digestive carbohydrase during larval development of meal moth, Plodia interpunctella (Lepidoptera: pyralidae)

The digestive system of P. interpunctella was characterized during its larval development to determination of carbohydrases using disaccharides (sucrose and maltose) and polysaccharides (starch and inulin) as substrate. At 6(th) instar larval, Invertase>alpha-amylase> maltase activities peaks were observed. Invertase was fractionated with acetone and isolated. The Invertase was 485.5 fold purified by Sephacryl S-200 and DEAE-Sephadex. Its kinetic parameters were K(m) of 6.6 mM, V(max) of 0.48, pH optimum of 5.5 and temperature optimum of 30 degrees C. This enzyme was activated by CaCl(2) and inhibited by EDTA. When analyzed by SDS-PAGE it showed one band of M(r) 34 kDa. The understanding of the digestive system of P. interpunctella could be a key step in the design of bioinsecticides.     

Diapause in twenty-three populations of Plodia interpunctella (Hübner) (Lep., Pyralidae) from different parts of the world

Abstract. 1. The incidence of diapause in twenty-three populations of Plodia interpunctella from fifteen countries representing all continents of the world was examined. The origins of populations varied from 52°N to 35°S and included two from equatorial regions.
2. Diapause occurred in all population samples at 20°C in short photoperiods (LD 11:13) and in continuous light, although the proportion of larvae doing so was less than 25% in samples from the equatorial belt.
3. The critical photoperiod was less than 13 h in five samples, all from the tropics, or southern hemisphere. The remaining samples, including three from the southern hemisphere, had critical photoperiods of 13 h or more.
4. Diapause was completely avoided by a 15 h photoperiod at 20°C in thirteen of the twenty-three samples, including all but one of those from the southern hemisphere.
5. At 25°C larvae entered diapause in short photoperiods (LD 9:15) in about half of the samples tested in both hemispheres, but the proportion per sample was always less than a third.     

Evaluation of long-term mating disruption of Ephestia kuehniella and Plodia interpunctella (Lepidoptera: Pyralidae) in indoor storage facilities by pheromone traps and monitoring of relative aerial concentrations of pheromone

The potential for pheromone-based mating disruption (MD) of Ephestia kuehniella (Walker) and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) was investigated in two flour mills and a pet food distributor. Plastic sachets emitting 2-3 mg per d (Z,E)-9,12-tetradecadienyl acetate, the major pheromone component of both moth species, were used as MD dispensers, which were applied in grid systems resulting in one dispenser per 100 m(3) of air volume. Pheromone traps with sticky inserts were used to monitor moth population fluctuations. To monitor pheromone levels in the air before, during, and after the treatment, electroantennographic (EAG) measurements were performed using a portable device. All localities showed decreased trap catches after application of MD. In two localities with low initial population densities, trap catches were reduced immediately after application of MD and remained very low, even several months after the MD treatment was terminated. In contrast, in a locality with a higher initial population density the reduction in trap catches was slower, and trap catches increased again soon after the termination of the MD treatment. Electrophysiological data showed not only increased aerial levels of pheromone during the treatment period but also levels that were higher than during pretreatment, even 12 mo after removal of MD dispensers. The localities had good ventilation, and the memory effect observed indicates that the pheromone adhered to surfaces that subsequently functioned as secondary dispensers. Customer complaints registered by one of the mills were 49% less in 2004, after 2 yr of MD compared with 2002, the year before the treatments began.     

The sensitivity of larval Plodia interpunctella and Ephestia elutella (Lepidoptera) to light during the photoperiodic induction of diapause

ABSTRACT. The incidence of diapause in larvae of Plodia interpunctella and Ephestia elutella held under two light systems was examined. Both systems progressively shortened the photophase of 24-h cycles, one with a motorized dimming switch providing dawns and dusks about 1 h long, the other switching the lights instantaneously. The mean critical photoperiod for P. interpunctella was about 131/4 h and for E. elutella just over 14 h. In both species light intensities as low as 0.2 lx influenced the induction of diapause. In P. interpunctella the critical photoperiod and sensitivity to light were similar at 23.±.;5°C and 20.5±0.5°C. At 22.5°C the percentage of diapausing larvae of E. elutella increased from 2% in long photoperiods (> 15 h light), to 100% in short photo-periods (t 12.5h light). Fox P. interpunctella , at 22.5°C the percentage increased from zero in long photoperiods (> 14 h light) to about 98% in short photoperiods (< 11.5h light), and at 20°C from 12% to 100% over a similar photoperiodic range. Similar results were obtained under selected fixed photoperiods, switched on or off instantaneously.     

Artificial carbon dioxide source to attract lesser cornstalk borer (Lepidoptera: Pyralidae) larvae

Different combinations of urea, urease (in jack bean meal, Canavalia DC.), and water were tested as carbon dioxide sources to attract larvae of lesser cornstalk borer, Elasmopalus lignosellus (Zeller), by using olfactory bioassays with an olfactometer and infrared gas analysis. A combination of urea, jack bean meal, and water was necessary to release a high level of carbon dioxide to attract the larvae. Different proportions of the three ingredients had different carbon dioxide release rates and exhibited different levels of attraction to the larvae. When carbon dioxide concentration was too high, attractiveness declined. Combinations with different amounts of water remained attractive for a period of up to 3 d, depending on the moisture of the samples. When Zonolite was used to simulate the soil conditions in the olfactometer, significantly more larvae located the area near the artificial carbon dioxide sources compared with the control. When combined with the artificial carbon dioxide sources, three insecticides (Lorsban, Temik, and Force) did not obviously affect the release rates of carbon dioxide, and more larvae were attracted to samples with the carbon dioxide source than to the samples without carbon dioxide.