Plodia interpunctella and Trogoderma variabile larval penetration and invasion of untreated and methoprene-treated foil packaging

Packaged food products inside retail stores and food warehouses are susceptible to infestation by stored-product insects. The insect growth regulator methoprene can be impregnated onto packaging materials to help limit stored-product insect population development and prevent infestations. The objectives of this study were to determine the effect of methoprene-treated foil packaging on egg hatchability and the penetration and invasion ability of the warehouse beetle, Trogoderma variabile Ballion, and the Indian meal moth Plodia interpunctella (Hübner). Twenty-five eggs of each species were added to Petri dishes containing untreated packaging or packaging containing 0.1, 0.25, and 0.5% of the active ingredient methoprene. Petri dishes were held for 7 d in an environmental chamber at 27 °C and 60% r.h. to determine percent hatchability of eggs. Additionally, 6 cm by 8 cm food packages were created from untreated and methoprene-treated packaging and placed into 0.18-L vials. First or third instars of each species were introduced into vials containing diet or no diet, to determine penetration ability after 21 and 42 d. In a separate experiment, packages were pierced with pinholes, and first instar T. variable or P. interpunctella were introduced and observed after 21 and 42 d for package invasion. The foil packaging had no significant effect on egg hatchability of either species. T. variabile were unable to penetrate or invade any foil packages. P. interpunctella invaded all packages containing pinholes. The methoprene-treated packaging reduced adult emergence of P. interpunctella and caused pupal and adult deformations in T. variabile. Methoprene-treated packaging presents a valuable option for food manufacturers to prevent insect infestations and maintain integrity of packaged food products.     

Effect of methoprene treated polymer packaging on fecundity,egg hatchability,and egg-to-adult emergence of Tribolium castaneum and Trogoderma variabile

The fecundity, egg hatchability, and egg-to-adult emergence of the red flour beetle, Tribolium castaneum (Herbst) and warehouse beetle, Trogoderma variabile Ballion, were evaluated on untreated and methoprene-treated polyethylene-to-polyethylene (PE-PE) and polyethylene terephthalate-to-polyethylene (PET-PE) packaging at 27 and 32 °C and 60% r.h. Inside and outside surfaces of the packaging were fit into ∼62 cm² Petri dishes, and 500 mg of flour (T. castaneum) or vanilla shake mix diet (T. variabile) were added to arenas as food for developing larvae. On methoprene-treated PE-PE packaging, hatchability of added T. castaneum eggs was consistently lower than on untreated packaging. On PET-PE packaging, hatchability of T. castaneum eggs on inside surfaces at both temperatures was significantly lower than on untreated packaging. No consistent trends were observed in T. variabilile hatchability between the packaging types, temperatures, and on inside and outside surfaces of untreated and methoprene-treated packaging. The fecundity of T. variabile was not significantly different between the packaging types. None of the T.castaneum eggs on inside and outside surfaces of the PE-PE methoprene-treated packaging emerged as adults. Methoprene-treated PET-PE packaging reduced fecundity of T. castaneum. Generally, hatchability of eggs laid by both species was not significantly different among the treatment combinations. Only the inside surface of PET-PE packaging gave 100% suppression of egg-to-adult adult emergence of T. castaneum. Development of T. variabile larvae was arrested at the pupal stage at both temperatures on the outside surface of methoprene-treated PE-PE packaging, whereas on the inside surface larvae completed development to adulthood. A 87–97% reduction in egg-to-adult emergence of T. variabile was observed on the inside surface of the PET-PE packaging relative to emergence in corrresponding control treatments at both temperatures. The packaging types evaluated in this study can potentially protect food products stored in these packages from infestations of T. castaneum and T. variable.     

Susceptibility of Tribolium castaneum and Trogoderma variabile larvae and adults exposed to methoprene-treated woven packaging material

Methoprene is an insect growth regulator (IGR) registered in the United States for direct application to stored raw grains, as an aerosol or residual contact insecticide, and for use as a coating for protection of packaged products. A series of tests was conducted to determine the adverse effects of short term exposure, sub-lethal exposure, and continual exposure of the red flour beetle, Tribolium castaneum (Herbst) and warehouse beetle, Trogoderma variabile Ballion, on methoprene-treated woven packaging material at 27 and 32 °C and 60% r.h. In the first test, larvae of both species were added to individual arenas and exposed for different time intervals, removed and resulting adult emergence was assessed. In the second test, eggs of both species were exposed on the packaging surfaces to determine percent egg hatchability. In the third test, adults of T. castaneum and T. variabile were added to arenas and held for 7 and 3 d, respectively, to determine number of eggs laid per female and subsequent egg hatchability. The eggs were held in arenas to determine the effect of continual exposure on egg-to-adult emergence. Results showed normal adult emergence decreased with increasing exposure time and temperature. Exposure to methoprene-treated packaging did not adversely affect fecundity of T. variabile adults, but did affect fecundity of T. castaneum. Continual exposure gave 100% suppression of T. castaneum adult emergence and a reduction of T. variabile emergence. This study indicated that methoprene-treated packaging could be a valuable addition to an existing integrated pest management program to increase protection of packaged products.     

Attraction of walking Tribolium castaneum adults to traps

The red flour beetle, Tribolium castaneum (Herbst), is a major pest of food processing facilities and can be monitored using pitfall type traps. To determine how beetles interact with these traps under field situations, the behavior of individual beetles released in the vicinity of traps was observed in a large arena. Specifically, the response of adults to traps baited with combinations of commercially available pheromone and kairomone attractants was measured, as was the influence of beetle sex and strain, airflow presence or absence, and distance from trap. The beetle's response to traps was strongest (e.g., more encountered trap, more remained in observation zone, more time was spent on treatment side, and decreased speed and increased turn angle) to pheromone/kairomone or pheromone baited traps when there was air movement, while kairomone alone and all attractants under still air conditions generated no significant response by the beetles. Even with the best combination of attractants and with airflow, average number encountering trap was only 40%. With airflow, beetles were successful at locating a pheromone/kairomone baited trap out to 90 cm, the maximum distance tested, but under still air conditions even at 10 cm there was no difference between traps with and without attractants. Since airflow at trap locations within commercial food facilities can vary considerably, these patterns of response to traps could significantly impact insect detection.     

Effectiveness of insecticide-incorporated bags to control stored-product beetles

Adults of seven stored-product beetle species were exposed on the inside and outside surfaces of polypropylene polymer bags incorporated with the insecticide deltamethrin (approx. concentration of 3000 ppm; ZeroFly^® Storage Bags (3 g/kg). Beetles were exposed for 60, 120, and 180 min, and 1, 3 and 5 days on the same treatment arenas, and after the 5 d interval the insects were removed and placed in untreated arenas for 5 more days. All Trogoderma variable (Ballion), the warehouse beetle, Prostephanus truncatus (Horn), the larger grain borer, Rhyzopertha dominica (F.), the lesser grain borer, and Tribolium castaneum (Herbst), the red flour beetle, were knocked down on the outside and inside surfaces of the bag after one hour of exposure. Mortality of T. variable, P. truncatus, and R. dominica increased during the exposure period, with generally lower mortality on the inside versus the outside of the bag after either 3 or 5 days of continual exposure. However, maximum mortality of T. castaneum, the red flour beetle, was only 5.6 ± 3.4% after 5 days of exposure. While it took longer for 100% knockdown of Sitophilus oryzae (L.), the rice weevil, compared to the above species, all S. oryzae were dead after 5 d of exposure on both surfaces. In contrast, after 5 days knockdown of Sitophilus zeamais (Motschlulsky), the maize weevil, did not exceed 30% and there was no mortality. After the Sitophilus species were transferred to untreated arenas, knockdown of all species decreased and mortality increased, indicating delayed mortality and no recovery from knockdown. Mortality of Dermestes maculatus (DeGeer), the hide beetle, did not exceed 5.6% at any time and there was no delayed mortality, indicating a potential tolerance of this particular strain of D. maculatus used in the study. Our results show that the ZeroFly^® Storage Bags could effectively limit penetration of stored-product beetles through the bag into stored grains or milled grain products.     

Aerosol concentration,deposition, particle size,and exposure interval as mortality factors Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae)

A series of trials was conducted for an experiment. In the first trial, adults of Tribolium confusum Jacquelin du Val, the confused flour beetle, were exposed on concrete arenas and treated with a combination aerosol of pyrethrin + methoprene dispensed for 5, 10, and 20 min at particle sizes of 4, 8, 12, and 16 μm, inside an aerosol exposure chamber. Nearly all adult T. confusum were knocked down when immediately removed from the chamber. Among all the exposure time and particle size combinations, recovery increased as the post-exposure holding period increased from one to seven days and when adults were transferred to untreated dishes with flour. A second experiment evaluated the residual effect of the aerosol on concrete arenas at 1, 3, and 6 weeks using 3-4-week-old larvae of T. confusum. Adult emergence of exposed larvae decreased with increasing particle size and exposure time. A biological index that assessed development of exposed larvae to the pupal and adult stages was also related to particle size and exposure interval, and this index was correlated with adult emergence. A third set of experiments investigated effects of particle size on adult fecundity for the 10-min exposure time. Male and female adults were cross-mated: exposed female with exposed male, exposed female with unexposed male, exposed male with unexposed female, and unexposed female and unexposed male. Progeny production was reduced as particle size increased, and there were indications that females were affected more than males by the aerosol treatment. This research could be used to improve insect pest management programs by adjusting application equipment to dispense aerosols at particle sizes that give optimum control of exposed adults and residual control of immatures and would also benefit pest management programs.     

Toxicity and repellency of dimethoate,pirimiphos-methyl and deltamethrin against Tribolium castaneum (Herbst) using different exposure methods

Tribolium castaneum, the red flour beetle, is one of the major pests of cereal grains and their products. Infestation of raw food products by T. castaneum can be tackled by use of insecticides which offer a rapid and effective control method for different insect pests. In the present study, toxicity and repellency of three widely used insecticides was assessed on adult red flour beetles to investigate how a flour substrate affects the results of the standard laboratory toxicity and repellency test methods. The red flour beetles were exposed to the organophosphates dimethoate and pirimiphos-methyl and the pyrethroid deltamethrin, following the original and two modified residual film methods (toxicity assessment) and by the area preference method to assess repellency. Since the conditions of exposure (glass and filter paper surfaces as exposure substrates) in the original methods are quite different compared to the exposure carried out in stored-product protection, methods were modified to include flour as an exposure substrate. The results showed that according to the LC₅₀ values, toxicity of the investigated insecticides could be arranged in the following order: pirimiphos-methyl > dimethoate > deltamethrin. Also, both mortality and repellency were dependent on the exposure methods, i.e. presence and treatment of flour substrate. Mortality was significantly reduced in comparison to the original method. Repellency was recorded when beetles were exposed to deltamethrin using flour as a substrate, whereas using the filter paper surface (original method) repellency was not obtained. The results of the present study clearly indicate that there is an influence of substrate on the susceptibility of T. castaneum to insecticides and that the efficacy of different insecticides is affected by exposure substrate.     

Effects of Cry1F and Cry34Ab1/35Ab1 on storage pests

Two crystalline protoxins from Bacillus thuringiensis (Bt), Cry1Fa1 and Cry34Ab1/Cry35Ab1 (Cry1F, Cry34/35Ab1), were evaluated for efficacy against lepidopteran and coleopteran storage pests. Cry1F was tested against the lepidopterans Sitotroga cerealella (Angoumois grain moth) and colonies of Plodia interpunctella (Indian mealmoth) that are susceptible or resistant to Bt Cry1Ab and Cry1Ac toxins, Bt subspecies entomocidus, and the commercial formulation Dipel^®. Cry1F was also tested against the coleopterans Cryptolestes pusillus (flat grain beetle) and Tribolium castaneum (red flour beetle). Cry34/35Ab1 was tested against S. cerealella, C. pusillus, and T. castaneum, and against additional coleopteran storage pests, including Tenebrio molitor (yellow mealworm), Trogoderma variabile (warehouse beetle), Oryzaephilus surinamensis (sawtoothed grain beetle), Rhyzopertha dominica (lesser grain borer), and Sitophilus oryzae (rice weevil). Strains of Bt-susceptible or -resistant P. interpunctella generally were more sensitive to Cry1A protoxin or toxin than either Cry1F protoxin or Dipel. Despite difficulties with the bioassay of S. cerealella larvae, the data suggest that Cry1F and Cry34/35Ab1 caused increased larval mortality, and a developmental delay was observed and no pupae emerged with 0.9% Cry1F. Neither Cry1F nor the corn rootworm-active toxin Cry34/35Ab1 significantly affected the biological parameters of the coleopteran species evaluated.     

Male-produced sex pheromone in Tribolium confusum: Behaviour and investigation of pheromone production locations

It is generally accepted that mating in flour beetles of the genus Tribolium is mediated by a male-produced aggregation pheromone. The pheromone production site in T. castaneum is believed to be glands on the ventral side of the femur. Behavioural experiments with the confused flour beetle T. confusum were conducted using extracts of beetles and different body parts as well as live beetles to investigate the responses to the complete odour bouquet released from the beetles. In our experiments, females but not males were attracted to male-produced volatiles, corresponding to the definition of a sex pheromone rather than an aggregation pheromone. SEM pictures confirm the occurrence of glands on all three pairs of legs of male T. confusum, but behavioural experiments show that females are attracted not only to extracts of male legs but also to whole body extracts and extracts of bodies without legs. These data suggest that in this species attractive compounds are produced not only in the glands on the femurs but also at multiple locations. Thus the pheromone systems involved in mating of flour beetles may be more complex than previously reported and differ among closely related species.     

Effect of mating disruption and lure load on the number of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) males captured in pheromone traps

A series of experiments examined the potential for using pheromone lures to monitor Indianmeal moth, Plodia interpunctella (Hübner), in the presence of mating disruption. When males were released in either the presence or absence of commercial mating disruption dispensers, the number of males captured in traps baited with synthetic pheromone lures increased with doses of 1–30 mg per lure (compared to 1–2 mg used in commercial monitoring lures). More males were captured in traps baited with synthetic pheromone lures than in traps baited with females as a pheromone source. The proportion of males captured in traps baited with synthetic pheromone lures vs. traps with females as a pheromone source changed with male age, but not with exposure to mating disruption dispensers. Male interaction with mating disruption dispensers was observed, and suppression of male capture in female-baited traps was quickly lost when mating disruption dispensers were removed. Implications of these findings for monitoring and semiochemical control of P. interpunctella are discussed.     

Aggregation pheromone 4,8-dimethyldecanal and kairomone affect the orientation of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) adults

Tribolium castaneum, the red flour beetle, is a major pest of stored products throughout the world. The male T. castaneum adults biosynthesize and release the aggregation pheromone 4,8-dimethyldecanal (4,8 DMD), and the monitoring traps having the synthetic form of this pheromone and kairomone are commercially available. However, certain information available on the response of T. castaneum adults to the strength of pheromone and the nature of air flow is inadequate and thus limits the potential use of this compound. The objectives of this research were to determine if the orientation of adult beetles to the synthetic form of the pheromone 4,8 DMD is affected by the distance from the pheromone, its concentration and air movement. Experimental design was completely randomized design with three replicates. The T. castaneum adults released at different distances from the pheromone placed at varying concentrations tested their orientation to the pheromone with the presence or absence of air flow. The control experiments were conducted without the pheromone. A separate experiment tested if exposure to 4,8 DMD alters the direction of movement in T. castaneum adults. The maximum trap catch (24%) was obtained with 0.5 μL of 4,8 DMD and when the beetles were released at distances up to 60 cm from the pheromone. The percentage of beetles trapped declined when the beetles were released 60–120 cm from the pheromone. The average angles on beetle turning during their orientation were significantly higher in the presence of pheromone than the respective controls. Air movement downstream of the pheromone trap increased the percentage beetles trapped compared to that in the absence of air flow. It is concluded that the orientation of T. castaneum adults is affected by the concentration of 4,8 DMD, distance from the pheromone and the air movement.     

A comparison between the impact of sulfuryl fluoride and methyl bromide fumigations on stored-product insect populations in UK flour mills

The impact of sulfuryl fluoride and methyl bromide fumigations upon populations of flour beetles (Tribolium spp.) and of Mediterranean flour moth (Ephestia kuehniella), was evaluated in UK flour mills. Two mills were selected for fumigation with sulfuryl fluoride and two mills for fumigation with methyl bromide. Traps baited with aggregation pheromone lure and an oil-based food attractant were used to monitor populations of rust red flour beetle and confused flour beetle. For the monitoring of Mediterranean flour moth, sticky traps baited with a pheromone lure were used. Traps were placed inside the mill buildings within the areas selected for fumigation. Infestation levels of the insects were monitored for 1–2 weeks prior to fumigation and for a total of 12 weeks post-fumigation. From the calculated percentage reduction in insects trapped per day during the post-fumigation monitoring period it was clear that sulfuryl fluoride fumigations had good efficacy against infestations of Tribolium confusum and E. kuehniella, and compared very favourably with the efficacy of methyl bromide. The absence of T. castaneum in traps pre-fumigation meant that the efficacy of sulfuryl fluoride against this species could not be assessed in this investigation. Indian meal moth, Plodia interpunctella, was also detected in some mills but only post-fumigation.     

Orientation of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) adults at various distances to different concentrations of aggregation pheromone 4,8-dimethyldecanal

Tribolium castaneum is a serious pest of durable agricultural commodities during storage. The male T. castaneum adults release the aggregation pheromone 4,8-dimethyldecanal (4,8 DMD). The 4,8 DMD is produced commercially and available to be used in Dome traps along with their recommended kairomone but low trapping response is often reported. Concentration of 4,8 DMD influences the attraction of T. castaneum adults but its intensity may vary under different warehouse settings. Further, the orientation response of T. castaneum adults from different distances to the synthetic 4,8 DMD is still uncertain. Therefore, the objective of this research was to evaluate the effect of distance to the traps having different 4,8 DMD concentrations on the orientation response of T. castaneum adults. The dome trap having two pheromone septa and kairomone was placed inside the experimental arena. From pheromone, different concentrations were used. One-month-old T. castaneum adults were individually marked and released from different distances at the same time. The adults reached the trap were counted 4 h following release. Alternatively the experiment was repeated without having the kairomone inside the trap. One trap having neither the pheromone nor kairomone (empty trap alone) and one having hexane only were used as controls. For all the pheromone concentrations used, the maximum trapping percentage was found when the beetles were released at 30 cm or 60 cm from the pheromone. Further, the highest trapping percentage was given by 0.5 μL of 4,8 DMD. At a given distance, the traps having pheromone+kairomone better attract T. castaneum adults than those had only the pheromone. The study concludes that the degree of attraction of T. castaneum adults varies with the distance from the trap and the trap composition. Further studies are required to test the efficacy of 4,8 DMD and kairomones under real warehouse settings.     

Metals in mandibles of stored product insects: do zinc and manganese enhance the ability of larvae to infest seeds?

Although high concentrations of zinc and manganese were found in mandibles of insect larvae that bore into seeds, these metals were not detected in mandibles of insect larvae that attack previously damaged seeds. Metals were present in the larval mandibles of a lepidopteran, the Angoumois grain moth (Sitotroga cerealella), and eight coleopterans, the lesser grain borer (Rhyzopertha dominica), cigarette beetle (Lasioderma serricorne), drugstore beetle (Stegobium paniceum), spider beetle (Gibbium aequinoctiale), warehouse beetle (Trogoderma variabile), cadelle (Tenebroides mauritanicus), larger black flour beetle (Cynaeus angustus), and cowpea weevil (Callosobruchus maculatus). Larvae of these species can chew into seeds. Larvae of six other coleopterans, the varied carpet beetle (Anthrenus verbasci), sawtoothed grain beetle (Oryzaephilus surinamensis), rusty grain beetle (Cryptolestes ferrugineus), red flour beetle (Tribolium castaneum), longheaded flour beetle (Latheticus oryzae), and granary weevil (Sitophilus granarius) have little if any ability to chew into seeds, and did not have metal in their mandibles. Larvae of the granary weevil hatch and feed within seeds that were penetrated previously during egg deposition by adults. However, newly hatched larvae of the cowpea weevil and the Angoumois grain moth have to bore through the seed coat before they begin feeding, and they have mandibles with high concentrations of zinc. These data support the hypothesis that deposition of zinc and/or manganese in larval mandibles enhances the larva's ability to penetrate seeds.     

Hemp (Cannabis sativa) seed for reproduction of stored-product insects

Hemp, or industrial hemp (Cannabis sativa), is a high value alternative crop that has seen increases in production in Canada since commercial production was legalized in 1998. Insect infestation of stored hemp seed may result in loss of quality and value. There are few published studies on the ability of insects to survive and reproduce on hemp seed. Reproduction of eleven stored-product insects on hemp seed at different moisture contents with, or without dockage, was studied. Insects were introduced into 15 g of hemp seed at two initial moisture contents (dry, 9% m.c. or damp, 15% m.c.), two dockage levels (dockage-free or dockage, 15%), and held at 30°C and 60–70% r.h. Five replicates of each treatment for each species were used. For beetles, twenty unsexed adults were used, for Ephestia kuehniella (Mediterranean flour moth), twenty eggs were used. For the beetles, live and dead adults were counted after 3, 5, 7 and 9 weeks, for the moth, adults were counted after 12.5 weeks. After counting, only live adults were returned to the hemp seed. The following beetle populations increased over the 9 weeks; Tribolium castaneum (red flour beetle), Lasioderma serricorne (cigarette beetle), Oryzaephilus surinamensis (sawtoothed grain beetle) and Trogoderma variabile (warehouse beetle). The following species did not increase their populations; Cryptolestes ferrugineus (rusty grain beetle), Rhyzopertha dominica (lesser grain borer), Sitophilus oryzae (rice weevil), Cryptolestes turcicus (flour mill beetle), Tribolium confusum (confused flour beetle), and Stegobium paniceum (drugstore beetle). For the beetles, higher dockage generally led to higher populations. The effect of moisture content was variable. Ephestia kuehniella produced adults on all treatments, with the dry treatment containing dockage performing the best.     

Efficacy of the auto-confusion system for mating disruption of Ephestia kuehniella (Zeller) and Plodia interpunctella (Hübner)

The auto-confusion system for stored-product pyralid moths, based on the contamination of adult males with the sex female pheromone (Z,E)-9,12-tetradecadienyl acetate (commercially known as TDA or ZETA), was evaluated. For this purpose, we applied Exosex SPTab dispensers that contained the Entostat™ powder, at a 5 × 5 m grid, in three facilities, one feed mill in Italy and two retail stores in Greece. In the feed mill, the most abundant pyralid species was Ephestia kuehniella. Monitoring through pheromone-baited traps in this facility indicated that the application of the Exosex SPTab dispensers decreased the number of captures 2 months after the initial application. In the case of the facilities in Greece, the most abundant species was Plodia interpunctella. In these facilities there was a continuous monitoring of moth populations from January 2008 until February 2011, with pheromone-baited traps and Petri dishes with semolina, which served as oviposition traps. In both facilities, the presence of P. interpunctella males in the pheromone-baited traps was reduced after the placement of the Exosex SPTab dispensers, in comparison to captures for the same interval from the previous years. At the same time, the number of emerging individuals in the oviposition traps was notably reduced after the Exosex SPTab dispensers placement, in comparison to the previous monitoring interval. Our study documents that the auto-confusion system is an effective and reliable technique that can be used with success against stored-product Pyralidae, to retail stores and feed mills.     

Evaluation of kaolinite-based particle films to control Tribolium species (Coleoptera: Tenebrionidae)

Adults of Tribolium castaneum (Herbst), the red flour beetle, and Tribolium confusum (du Val), the confused flour beetle, were exposed to kaolinite-based particle film dusts. When beetles were continuously exposed to the hydrophobic particle film M-96-018 at the rate of 0.1-0.5 mg/cm², all the T. castaneum at 0.1 mg/cm² were dead after 3 days, but 40±13.8% of the exposed T. confusum were still alive after 7 days. At higher concentrations, all the T. castaneum were dead after 2 days, but 5-6 days of exposure were needed to kill all T. confusum. In a subsequent test, adults of both species were exposed for 8-72 h to 0.5 mg/cm² of the particle film M-96-018, removed, then held without food for 1 week. No T. castaneum survived, while survival of the T. confusum ranged from 0 to 55±17.3%, depending on the exposure interval. In a test conducted at controlled conditions of 40%, 57% and 75% r.h., 27°C, T. confusum were exposed for 8-72 h to the particle film M-96-018 and a hydrophilic particle film M-97-009 at the rate of 0.5 mg/cm², then removed and held either with or without wheat flour for 1 week. All the T. confusum exposed to the particle film M-97-009 usually survived, while survival of the T. confusum exposed to the particle film M-97-018 after the 1-week holding period increased with increasing relative humidity and with the presence of food. The particle film M-96-018 was effective against both the Tribolium species, and appears to have a potential for use in management programs to control beetles within storage facilities.     

Initial and delayed mortality of late-instar larvae, pupae, and adults of Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae) exposed at variable temperatures and time intervals

Late-instar larvae, pupae, and adults of Tribolium castaneum (Herbst), the red flour beetle, or Tribolium confusum (DuVal), the confused flour beetle, were exposed for variable durations at 36-54 °C. Beetles were placed in laboratory ovens set at a baseline of 27 °C, the temperature was increased by 0.1 °C per minute until the target temperature was achieved, and beetles were then held for specified exposure durations. There was no mortality after initial exposure or after a 1-week holding period of any life stage of T. castaneum or T. confusum exposed for 32 h to 36, 39, or 42 °C. At 45 °C, there was no initial mortality of either species exposed for different time intervals except for those exposed for 28 h. However, there was a significant increase in mortality after the 1-week holding period of those beetles exposed initially for at least 16 h to 45 °C. There was a sharp increase in mortality after the initial exposures of 4 h at 48 °C; mortality of T. confusum larvae was 90.0±5.7% but was only 10.0±10.0% for larvae of T. castaneum, and no pupae of either species were dead. All life stages of both species were killed after the initial exposure of 12 h, and 1-week mortality of beetles exposed for 4 and 8 h was generally greater than initial mortality. At 51 and 54 °C, 2- and 1-h exposures, respectively, killed all life stages of each species. Mortality in conditions of gradual temperature increase was less than previous studies with sudden temperature increases.     

Efficacy of filter cake and Triplex powders from Ethiopia against three externally developing stored product insect species

Efficacy of filter cake and Triplex powders was evaluated against the red flour beetle, Tribolium castaneum (Herbst); saw-toothed grain beetle, Oryzaephilus surinamensis (L.); and Indian meal moth, Plodia interpunctella (Hübner). Mortality of T. castaneum and O. surinamensis was determined 14 d after exposing 20 adults to 100 g of maize and wheat treated with 0, 0.3, 0.5, 0.7, 1, 2, and 3 g/kg of filter cake and 0, 0.5, 0.7, 1, 2, 3, 6, 8, and 10 g/kg of Triplex. Adult progeny production was determined at 42 d. Live larvae at 21 d and adults of P. interpunctella that emerged at 42 d were determined by exposing 100 eggs to 0, 0.2, 0.3, 0.5, 0.7, 1, 2, and 3 g/kg of filter cake and 0, 0.3, 0.5, 0.7, 1, 2, 3, 6, and 8 g/kg of Triplex treated maize and wheat. On both grains, 100% mortality of T. castaneum and O. surinamensis adults was observed after exposure to 2–3 and 1–3 g/kg of filter cake, respectively. On wheat, 100% mortality only of O. surinamensis was observed in 2–3 g/kg Triplex treatment. Adult progeny production of T. castaneum and O. surinamensis was completely suppressed on both grains treated with 0.7–3 g/kg of filter cake. Adult progeny production of T. castaneum was completely suppressed at 1–3 g/kg of Triplex treated grains, whereas complete suppression of O. surinamensis was achieved only on maize treated with 2–3 g/kg of Triplex. Both live larvae at 21 d and adults of P. interpunctella that emerged at 42 d were completely suppressed when eggs were exposed to 2–3 and 0.5–3 g/kg filter cake treated maize and wheat, respectively, and on 6–8 and 3 g/kg Triplex treated maize and wheat, respectively. Filter cake was more efficacious compared to Triplex on both grains.     

A potential method for simultaneous,semiochemical-based monitoring of Cryptolestes ferrugineus and Tribolium castaneum (Coleoptera: Cucujidae and Tenebrionidae)

Capture and analysis by gas-liquid chromatography of volatiles from adult Cryptolestes ferrugineus (Stephens) infesting rolled oats disclosed that the naturally-produced ratio of the aggregation pheromones 4,8-dimethyl-(E,E)-4,8-decadienolide (I) and (3Z, 11S)-dodecen-11-olide (II) is 1.6:1.0. Approximately 990 and 640 pg/male beetle/h of the 2 pheromones, respectively, were produced in a culture with 76 beetles of mixed age and sex/g of oats. A newly designed trap, which confines beetles responding to attractive odors within an enclosed chamber, was very effective in recapturing released C. ferrugineus when baited with a 13:16 mixture of I and (±)-II released at 1.25 μg/24h, and also in recapturing released adult Tribolium castaneum (Herbst), in response to the aggregation pheromone, 4,8-dimethyldecanal, released at 0.08 μg/24h. Moreover, the capture of each species to traps baited with both species' pheromones was no different than to traps baited with its pheromone alone. Thus the pheromones of both species can be used together in the same trap in semiochemical-based, pest monitoring systems.