Effects of gamma irradiation on fourth-instar Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

Effects of gamma irradiation on fourth-instar Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) larvae in infested dates (Boufeggous variety) were assessed. Larvae were exposed to different gamma irradiation doses ranging from 300 to 900 Gy. Feeding, pupation, adult emergence and survival were very sensitive to ionizing irradiation. When irradiated at a dose of 300 Gy and higher, food consumption and weight gain were significantly affected, in a dose-dependent manner. Twenty days after irradiation, the weight loss at doses of 300, 450 and 600 Gy was 42%, 47% and 49%, respectively. At doses of 750 and 900 Gy, the weight of larvae diminished by 51% and 54%, respectively. In contrast, the controls gained 20% in weight. Development of larvae to the pupal stage was not prevented completely but none of the pupae emerged as adults. At 300 Gy, 21% of larvae survived 44 d after irradiation and successfully pupated. An absorbed dose of 450, 600, 750 or 900 Gy applied to larvae caused 100% mortality by 44, 38, 38 and 22 d post-treatment, respectively. The minimum dose required to prevent damage from feeding and adult emergence was 300 Gy while doses required to cause death were ?450 Gy.     

Effects of gamma irradiation on the development and reproduction of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

The inhibitory effects of gamma irradiation were demonstrated on the development and reproduction including egg hatch, pupation, adult eclosion and oviposition of Plodia interpunctella. Failure of all these events increased with increasing doses from 0.1 to 1.0 kGy. However, the rates of developmental inhibition were different among three behavioral events. Egg hatch was almost completely inhibited by 0.5 kGy and higher doses. Pupation was completely inhibited by 0.25 kGy, but adult eclosion was not completely inhibited even by 1.0 kGy. In addition, different age groups within the egg and final larval stages differed in their susceptibility to 0.1 and 0.25 kGy doses; the rates of both hatching and pupation were lower when young individuals were irradiated. Fecundity and hatchability of eggs were greatly reduced when pupae were irradiated at 0.1 kGy and completely inhibited at 0.25 kGy and higher doses. This suggests that although some adults eclosed from pupae irradiated at 0.25 kGy and higher doses, they were not able to lay eggs. Our results suggest that irradiation at 0.5 kGy is appropriate for the inhibition of development and reproduction of P. interpunctella.     

Methoprene and synergized pyrethrins as aerosol treatments to control Plodia interpunctella (Hübner), the Indian meal moth (Lepidoptera: Pyralidae)

Aerosol insecticides (also known as ULV or fogging treatments) delivered through an ultra-low-volume application system, are available commercially to control insect pests such as Plodia interpunctella Hübner, the Indian meal moth. However, little is known about the susceptibility of eggs of P. interpunctella to aerosol insecticides applied in active field sites. We conducted several trials by exposing eggs of P. interpunctella to synergized pyrethrins, alone and in combination with the insect growth regulator methoprene. Eggs in diets and packaging materials containing the food products were directly exposed to the aerosols. There was significant variation among the food products, as assessed by adult emergence from exposed eggs, but in general there was no difference in adult emergence from eggs exposed to a 1% versus a 3% pyrethrin formulation when methoprene was included. There was no difference in efficacy between diets and diet packages placed in open areas versus areas that were in some way obstructed to the aerosol. Adult emergence was generally reduced in the treatment combinations compared to untreated controls. A partial budget analysis indicated that the combination treatment of 1% pyrethrins + methoprene represented the lowest risk, lowest cost, and would seem to be the optimum combination. Results show that field applications of aerosols could be used to control P. interpunctella in storage facilities.     

Development, reproduction, and control of the Indian meal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), in stored seed garlic in Mexico

Developmental time, fecundity, and egg hatch rate were determined for the Indian meal moth, Plodia interpunctella (Hübner), reared on fresh garlic seed at room temperature in Mexico. Duration of the egg stage averaged 4.7±0.8 days with an egg hatch rate ranging from 82% to 95%. Five larval instars were determined based on head-capsule width. Total larval developmental time from egg hatch to adult emergence ranged from 42 to 47 days. Adult females began to oviposit within 12-48 h after mating with the maximum oviposition rate occurring during the first 24 h after mating. The mean (±SE) number of eggs laid by females was 212±34 with a range of 117-303. Application of pirimiphos-methyl, malathion, and permethrin to 30 kg lots of garlic seed failed to prevent infestation and bulb damage by the larvae. However, compared with controls, the percentage of damaged bulbs and the number of larvae detected during 12 weeks of storage was smaller on garlic treated with four doses of pirimiphos-methyl.     

Oviposition attractants for Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) in the volatiles of whole wheat flour

Plodia interpunctella is attracted to whole wheat flour. Volatiles obtained from whole wheat flour by Porapak Q trapping were assayed using pitfall olfactometers, and were attractive to mated females (active at 10⁻¹ gram/day equivalent, gde), but not to males or unmated females, suggesting that the volatiles are oviposition attractants for P. interpunctella. Silicon dioxide column chromatography of the crude volatiles revealed that the fraction recovered with 3% ether in pentane (3% EP) was active and contained at least 27 components, in which alkanals (C₆-C₁₀) and 2E-alkenals (C₇-C₁₁) were active as individual aldehydes or mixtures. Nonanal was most active (the lowest active limit, LAL: 10⁻² μg), followed by 2E-nonenal and 2E-decenal (1 μg each). The synthetic mixture of the 27 components identified from 3% EP was attractive at 1.59×10⁻⁴ μg, which was equal in activity to the crude volatiles at 10⁻¹ gde (LAL) for mated females. The ether fraction (E) showed no activity by itself but synergistically enhanced the activity of the 10% EP fraction (LAL: 10⁻⁴ μg). Alkanols (C₅-C₉), lactones and carboxylic acids (C₅-C₁₈) were identified from the E fraction, in which hexanol and hexanoic acid were the major components. Both hexanol and palmitic acid were synergistic in combination with the aldehyde mixture.     

A wild strain of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) from farm-stored maize in South Carolina: Development under different temperature, moisture, and dietary conditions

The purpose of this study was to determine the duration of immature development and survivorship of Plodia interpunctella (Hübner) on maize over a range of temperatures and grain moisture contents encountered in maize stored on farms in the southeastern states (USA). Laboratory cultures were established with moths collected from farm-stored maize in South Carolina and maintained on cracked maize at 30 °C and 60% r.h. The incubation period and percentage hatch of eggs was determined at 18 combinations of temperature and r.h. Hatch was <1% at 15 and 40 °C. In the range 20-35 °C, percentage hatch declined as temperature increased, and the mean incubation period ranged from 3.1 to 8.5 d. Neither percentage hatch nor incubation period were affected by r.h. between 43% and 76%. The relationship between mean developmental period (oviposition to adult eclosion) and temperature was well described by a quadratic polynomial that predicted a decline from 67.6 to 30.1 d as temperature increased from 20 to 31.1 °C, followed by an increase to 38.5 d as temperature increased further to 35 °C. The results suggest a lower temperature threshold for development near 15 °C and an upper limit slightly greater than 35 °C. Moisture content had a significant effect on developmental period at all the temperatures studied, but the pattern of variation with moisture depended upon the temperature.     

Comparison of direct and indirect sampling procedures for Plodia interpunctella in a maize storage facility

Weekly sampling of the Indian meal moth, Plodia interpunctella, was conducted over 15 consecutive weeks at 19 locations within a maize storage facility. Direct sampling consisted of maize samples from two depths from the maize surface, and was compared with three indirect sampling techniques: (1) cardboard traps intended for trapping of late instar larvae and pupae; (2) unbaited sticky traps at two heights above the maize intended for trapping adults; and (3) probe traps inserted into the maize intended for trapping both larvae and adults. Temperature was recorded weekly and maize moisture content every 2 weeks at each sampled location. Total catches for the entire sampling period were highest with cardboard traps followed by maize samples, sticky traps, and probe traps. Spatial statistics were used to examine the distribution pattern of weekly catches for each sampling technique: (1) larvae in both top and bottom maize samples indicated similar aggregated distribution patterns; (2) catches with cardboard traps and sticky traps at both heights suggested a random distribution pattern; and (3) catches with probe traps were considered too low for analysis. For each weekly sampling event, the level of spatial association between sampling techniques was investigated in which the spatial distribution of larvae in top samples was compared with: (1) larvae in bottom maize samples; (2) cardboard trap catches; and (3) adults sticky traps. Catches of adults in low sticky traps were compared with: (4) adults in high sticky traps; (5) cardboard trap catches; and (6) larvae in bottom maize samples. Of the six spatial associations, only larvae in the top and bottom maize samples were significantly associated, while there was no significant spatial association involving catches with indirect sampling techniques. We used response surface regression analysis to evaluate the relative contribution of six explanatory variables in a model fitted to the abundance of larvae in maize samples (order of importance): y-coordinate of sampling locations, vertical position of samples, temperature, number of weekly sampling event, moisture content, and x-coordinate of sampling locations. Using additional response surface regression analyses with the same explanatory variables, we showed that abundance of larvae in maize samples was a poor predictor for the occurrence of P. interpunctella individuals in indirect samples. The implications of different spatial distribution patterns for different sampling techniques of P. interpunctella are discussed.     

Moisture content in a wheat germ diet and its effect on the growth of Plodia interpunctella (Hübner)

The growth rate of Plodia interpunctella larvae feeding on wheat germ was highly dependent upon the water content in the diet. The water content in a cereal diet is established by the hygroscopicity of the dietary components and the relative humidity (r.h.) in the equilibrating atmosphere. The larval growth rates on wheat germ increased with corresponding increases in r.h. over the range of 40-85%. Similar changes in r.h. had a measurable, albeit minimal, impact on the time required for embryonic development and egg hatch. The water content of wheat germ was further increased by supplementing the germ with the humectant, glycerol. The larval growth rate increased with each incremental increase in dietary water content irrespective of whether it resulted from increases in r.h. or glycerol. However, glycerol supplementation provided an additional boost to the growth rate that was in addition to and distinct from the dietary water increase.     

Behavior and movements of Indian meal moths (Plodia interpunctella Hübner) during commodity infestation

A model warehouse with carefully regulated environmental conditions was used to study the behavior of adult Indian meal moths during commodity infestation. Sequences of moth distributions in the warehouse, calculated by spatial analysis, clearly showed the coordinated movements of moth populations from eclosion to death. Many facets of adult behavior in a warehouse were coordinated with the photoperiod. Adult moths emerged at the end of a photophase and fairly rapidly moved to the walls and, to a lesser extent, to the undersides of the commodity pallets. Most females are mated in the first 24 h after emergence, largely during the scotophase. Air circulation within the warehouse probably compromised pheromone-directed guidance of males to females, although pheromones may still have a major role in regulating other aspects of male mating behavior. When mating subsided, many of the males flew upwind to the air circulating unit, but only during the photophases. The females moved to the return air side of the warehouse and then migrated towards the same end as the males, but only during the scotophases. They moved from pallet to pallet largely by walking on the warehouse floor and laid eggs in or on the cups of commodity. Direct oviposition on the commodity during the infestation period was lower than expected, probably because commodity odors were dissipated by air circulation and did not provide appropriate orientation. At 144 h after emergence, 90% of the moth population had died.     

Low-temperature aeration to control Indianmeal moth, Plodia interpunctella (Hübner), in stored grain in twelve locations in the United States: a simulation study

Aeration management strategies were developed to control cold-acclimated and diapausing Indianmeal moth, Plodia interpunctella (Hübner), larvae in grain bins during winter in north- and east-central regions of the US. The application in this study focuses on corn because it is the dominant crop in these regions, but we believe that the analyses can be applied to other grains as well. Contour maps for hours below −10 °C for the months of December, January, and February were developed to help effective planning and management of aeration to control overwintering stored-grain insects. Two cumulative lethality index (CLI) models were developed to estimate mortality of laboratory-reared (diapausing without cold-acclimation) and field-collected (cold-acclimated, and diapausing with cold-acclimation) P. interpunctella larvae under changing temperature conditions. The CLI models were used for evaluating aeration management strategies. Simulation studies were conducted using 30 years of weather data for 12 locations in north- and east-central regions of the US to evaluate different aeration management strategies for controlling P. interpunctella larvae. For each strategy, temperatures of headspace air and grain in the top meter of the grain mass were simulated using an existing model for the period of December-February. The tested management strategies included no aeration, continuous aeration, and intermittent aeration by controlling fan operation. During aeration, air was pulled from the headspace downward through the grain with an airflow rate of 0.11 m³/min-t (0.1 cfm/bu). Simulation results indicated that a fan control strategy that turned the aeration fan on when the grain temperature at 0.4-m depth was greater than the headspace-air temperature was the best strategy for managing P. interpunctella larvae in all tested locations. For this strategy, the CLI model indicated that 100% mortality of P. interpunctella larvae could be achieved at a grain depth of 0.4 m from the top grain surface in all locations. For this strategy, the aeration fan operated about 10% of the time from December to February. The average cost of electrical energy required for aeration fan operation with this strategy for all locations was 1.3 ¢/t (0.033 ¢/bu) based on an electrical energy cost of 7 ¢/kWh.     

Enhanced oviposition in the moth, Plodia interpunctella, after treatment with aminergic analogues

In many species of moths, including Plodia interpunctella, post-mating events include the cessation of sex pheromone communication and the initiation of oviposition. In a previous study we have shown that octopamine and several analogues inhibit the production of sex pheromone in the moth. The present study demonstrates that octopamine and two analogues, clonidine and 2-(2,6-dimethylanilino) imidazolidine induce oviposition by virgin females of P. interpunctella, to a comparable level to that of mated females. Moreover, octopamine caused a significant reduction in the percentage of fertile eggs laid by mated females. It is suggested that octopamine therefore, mimics both the responses that occur post-mating: suppression of sex pheromone biosynthesis and stimulation of oviposition.     

Biology, behaviour and environmentally sustainable control of Tineola bisselliella (Hummel) (Lepidoptera: Tineidae)

This review summarises the information available on the biology, behaviour and economic significance of the common or webbing clothes moth, Tineola bisselliella (Hummel), currently the most important and widespread clothes moth pest throughout the world. These moths can cause the loss of irreplacable material of aesthetic, historic and scientific importance, as well as damaging every-day items such as clothes, furnishings and other materials prepared from animal fur, wool, feathers and hides. Methods for the detection and control of this pest are outlined, with particular emphasis on control strategies that are environmentally sustainable and avoid the use of conventional pesticides and fumigants. Improvements in storage coupled with targeted use of appropriate control measures will help to reduce pest populations. However, the continuing problems with this pest highlight the need for improved methods of detection, prevention and management.     

Insecticidal effect of Steinernema feltiae (Filipjev) (Nematoda: Steinernematidae) against Tribolium confusum du Val (Coleoptera: Tenebrionidae) and Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) in stored wheat

The confused flour beetle, Tribolium confusum, and the Mediterranean flour moth, Ephestia kuehniella, are important pests of stored grain products. The insecticidal effect of three strains (UK 76 [=Nemasys], USA/SC, and Hawaii) of the entomopathogenic nematode Steinernema feltiae was determined in the laboratory, in wheat, against these pests. The nematodes were applied at three dose rates: 100, 300 and 900 nematodes/insect individual. The Hawaii strain was most virulent against T. confusum adults and larvae, with a significant dose effect in the case of the larvae. Larval mortality of this species reached 79% and 100% after 7 and 14 d of exposure to the nematodes, respectively, at the highest dose applied. On the other hand, adult mortality of T. confusum did not exceed 66%. In the case of E. kuehniella larvae, USA/SC performed best causing 52% and 69% mortality after 7 and 14 d exposure, respectively, at the highest dose tested. Since very few data are available on the effect of entomopathogenic nematodes against these pests, it is concluded that the Hawaii and USA/SC strains of S. feltiae should be further investigated as promising biological control agents for T. confusum and E. kuehniella.     

Predation by Blattisocius tarsalis (Berlese) (Acari: Ascidae) on eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

The mean predation rate of female B. tarsalis on eggs of E. kuehniella was determined at 15°C, 21°C, and 27°C with prey densities of 3, 5, 10 and 15 eggs. Young eggs less than 24 h old were used as prey. Under all experimental conditions most eggs were only partially consumed, confirming the general theory that predatory mites leave most of the food content unutilized. A mean predation rate of 2.2-7.0 eggs destroyed in 24 h was found, reflecting that a large proportion of the available prey was destroyed. The result supports the view that the predatory mite B. tarsalis could be a relevant biological control agent against E. kuehniella in flour mills. It was further demonstrated that frozen moth eggs can be considered as an appropriate food source.     

Inheritance of resistance to malathion,DDT and dieldrin in Plodia interpunctella (Lepidoptera: Pyralidae)

Diagnosis of heterogeneous resistance in a field strain of Plodia interpunctella enabled selection to be made of a susceptible and three resistant strains with resistances specific to malathion, DDT or dieldrin respectively. Resistance in F1 larvae from crosses between susceptible and resistant moths was intermediate for each resistance. Diagnostic doses were used to determine the mode of inheritance for the three resistances. Tests on larvae from F2 crosses and repeated back-crosses showed that resistance to malathion was due to a semi-dominant gene. Tests on F2 and first back-cross larvae suggested that resistance to DDT and dieldrin was also explicable in terms of distinct single, semi-dominant genes.     

Effects of different food commodities on larval development and α-amylase activity of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

The present work was undertaken to study the influence of four commodities (wheat flour, dates, sorghum and barley) on Plodia interpunctella post-embryonic development. Larval weight, larval mortality, pupation and adult emergence were recorded. The study also aimed to find out the effect of these commodities on protein and glycogen production as well as on α-amylase activity. Results indicated that the weight of fourth instar larvae placed on dates increased gradually. Percentage mortality was low. Pupation and adult emergence were delayed. In contrast, the weight of larvae placed on wheat flour, sorghum or barley remained low. Pupation and adult emergence occurred sooner than among those placed on dates and the percentage mortality was highest for larvae placed on barley. Results also showed that protein content and α-amylase activity were lower for larvae placed on dates than for those placed on other commodities. The biochemical composition of different commodities showed that dates are a rich source of glucose, while their protein and starch contents were very low as compared to the other commodities. In contrast, wheat flour, sorghum and barley contained large amounts of starch and protein and low amounts of glucose. Thus, the reduction in α-amylase activity was probably due to the high levels of glucose in dates.     

The effect of a granulosis virus on Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) infestations occurring in stored raisins

Neonate larvae of Plodia interpunctella (Hübner) were exposed to 5 different concentrations of a granulosis virus (GV) on raisins; the estimated LC₅₀ was between 1 × 10³ and 1 × 10⁴capsules/ml of suspension. Raisins treated with 1 × 10⁸capsules/ml GV suspension were protected from P. interpunctella infestation for at least four months under normal storage conditions. The treated raisins retained the GV inoculum after 5 min of water washing. Field-run raisins treated with GV in two separate tests (14 and 9 weeks) reduced moth populations by 95.2% and 96.9%. Treatment with GV of processed raisins prior to packaging and of the packages themselves (containing raisins) reduced moth populations over a six-month period by 75.5% and 33.2%, respectively.     

Effect of host density on egg dispersion and the sex ratio of progeny of Bracon hebetor (Hymenoptera: Braconidae)

Egg dispersion and the sex ratio of progeny were studied in relation to the host density of the parasitoid, Bracon hebetor Say, infesting larvae of Plodia interpunctella (Hübner). Females appeared to allocate eggs in relation to host density to avoid laying more eggs than could complete development on a host. The dispersion pattern of the parasitoid ovipositions among hosts was influenced by host density. Multiple visitations and ovipositions by females on hosts caused a highly aggregated pattern at low-host densities. Hatch rate of eggs decreased as the number of eggs on a host increased. Females seemed to regulate progeny sex ratio (male/total) based on the number of eggs on the hosts and the clutch size of the hosts they encountered. However, the overall progeny sex ratio remained at approximately 0.5 regardless of host density, probably because the allocation of eggs was related to host density.     

Some aspects of the biology of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), a pest of stored groundnuts in Nigeria

The biology of Plodia interpunctella (Hübner) was studied at various combinations of temperature and relative humidity. The incubation period of eggs ranged from 4 to 7 days. Development from laying of egg to adult lasted an average of 50.9 days at 25°C and 60% r.h. and 34.6 days at 30°C and 80% r.h. At 70 and 80% relative humidity, development was faster, more progeny were produced and the moths were heavier than at 60% r.h. Relative humidity had little effect on egg and pupal development.The larvae were negatively phototactic. However, the rate of development of the strain studied was similar in constant darkness, constant light or in a 12 hr-light: 12 hr-dark light system. The adult moths were immobile in diffused daylight. Locomotory activity was markedly high at dusk and was accompanied by an increase in the rate of pairing. Temperatures between 27 and 31°C did not appear to influence locomotory activity.Cracked groundnuts were more favourable for development than whole nuts which were in turn better than groundnut meal. The weight losses inflicted on infested groundnuts were directly correlated with the total weights of emerged moths and differed according to the treatment given to the medium. Losses in weight of about 8.7 and 8.6% were observed when 13 larvae completed development in 30 g of whole nuts and cracked nuts, respectively. Females consumed more food and were heavier than the males. Each larva ate an average of 140 mg of whole nuts and 190 mg of cracked groundnuts to complete development. The increases in free fatty acid values were not appreciably higher in infested media than in the control. Increases of 17.5 and 18.2 m-equiv of peroxides were observed in infested whole and cracked nuts, respectively.