Different diets affecting biology and digestive physiology of the Khapra beetle,Trogoderma granarium Everts (Coleoptera: Dermestidae)

The Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is a serious pest of grain and other stored products through the world. In this research, effect of five host diets including barley, rice, rye, wheat and walnut was studied on some of biological traits, nutritional indices and digestive enzymatic activity of T. granarium at 33 ± 1 °C, 65 ± 5% RH and a photoperiod of 14:10 (L:D) h. The Khapra beetle larvae reared on walnut had the highest number of larval instar and longest duration of larval and pupal stages (91.30 ± 0.4 days). The heaviest pupal weight of T. granarium was on rye (4.22 ± 0.01 mg) and the lightest weight was on rice (3.99 ± 0.01 mg) and walnut (4.00 ± 0.01 mg). The highest realized fecundity and fertility were recorded for the females reared on rye (45.88 ± 1.08 eggs/female and 69.39 ± 0.68%, respectively) and wheat (49.02 ± 1.55 eggs/female and 67.54 ± 0.69%, respectively), and the lowest ones were observed for the females came from larvae fed walnut (15.45 ± 0.71 eggs/female and 34.55 ± 0.82%, respectively). Also, the results showed that T. granarium larvae reared on walnut had the lowest values of the efficiency of conversion of ingested food (7.67 ± 0.04%) and relative growth rate (0.044 ± 0.0002 mg/mg/day). The lowest midgut amylolytic (0.044 ± 0.0005 and 0.047 ± 0.0005 mU/individual, respectively) and proteolytic (0.015 ± 0.0004 and 0.016 ± 0.0001 mU/individual, respectively) activity of the sixth instar was detected on walnut and rice. The highest inhibition of amylase (53.37 ± 0.75%) and protease activity (48.54 ± 0.96%) was estimated by incubating midgut extracts from the last instars with wheat and barley proteinaceous extracts, respectively. The results indicated that walnut was the most unsuitable diet for feeding and development of T. granarium.     

Effect of three entomopathogenic nematode species to Trogoderma granarium Everts (Coleoptera: Dermestidae) larvae on stored-wheat

Grain commodities are subjected to multiple insect infestations during processing and storage. The kharpa beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae) is categorized as a destructive stored-product pest due to its elevated survival potential, preference for dry conditions and resistance to many insecticides. While public concern about pesticide related risks increases, the development of alternative, environmentally more benign disinfestation methods of stored commodities is pursued. The current study evaluated the effectiveness of three entomopathogenic nematodes, Heterorhabditis bacteriophora Poinar (Rhabditita: Heterorhabditidae), Steinernema carpocapsae (Weiser) (Rhabditita: Steinernematidae) and Steinernema feltiae (Filipjev) (Rhabditita: Steinernematidae) against small and large larvae of T. granarium. Suspensions of nematodes were applied at six doses: 100, 500, 1000, 5000, 10000 and 50000 infective juveniles (IJs)/ml of water on wheat at 30 °C. Mortality of larvae was estimated 4 and 8 days post-exposure to nematodes. All three entomopathogenic nematodes were able to cause mortality on the insect. High mortality rates were accomplished by the two Steinernema species. The most efficient entomopathogenic nematode against small larvae was S. feltiae which attained 98.9% mortality followed by S. carpocapsae which caused 91.1% mortality after 8 days of exposure. Similarly, S. feltiae and S. carpocapsae killed 87.8 and 63.3% of the exposed large larvae on wheat treated with 50000 IJs/ml after 8 days of exposure. In contrast, at the highest dose, H. bacteriophora was less effective than S. carpocapsae and S. feltiae since it caused 76.7 and 60.0% mortalities to exposed small and large larvae after 8 days of exposure. The effectiveness of all three entomopathogenic nematodes was increased at higher doses and longer exposures. The findings of the current study indicate that entomopathogenic nematodes are efficient biological control organisms of T. granarium larvae infesting stored-wheat.     

Maize hybrids affected nutritional physiology of the khapra beetle,Trogoderma granarium Everts (Coleoptera: Dermestidae)

The Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is an important insect pest of stored cereals, grains and other stored products in Iran and some countries of the world. Nutritional indices and digestive enzymatic activity of fifth instar T. granarium were investigated on nine maize hybrids (704, AR 89, AS 71, AS 77, BC 678, KSC 703, PL 472, SC 704, and Simax) at 33 ± 1 °C, relative humidity of 65 ± 5%, and a photoperiod of 14: 10 (L: D) h. The highest and lowest food consumption by larvae was on AR 89 and BC 678, respectively. Fifth instar larvae fed on 704 had the highest efficiency of conversion of ingested food, and those fed on BC 678 showed the lowest relative growth rate. The larval growth index, standardized insect-growth index and fitness index were the highest when larvae were reared on PL 472, and the lowest when they were reared on BC 678. The highest proteolytic and amylolytic activity was on KSC 703, and the lowest activity was on BC 678. The results of this study indicated that BC 678 was an unsuitable hybrid for feeding of fifth instar T. granarium. Studying the nutritional physiology of T. granarium on different maize hybrids can be useful in identifying the anti digestive compounds of host grains, which can be expressed in genetically engineered crops to confer resistance to this key pest.     

Susceptibility of Trogoderma granarium Everts and Trogoderma inclusum LeConte (Coleoptera: Dermestidae) to residual contact insecticides

Commercial formulations of the pyrethroid insecticides β-cyfluthrin and deltamethrin were evaluated for delayed mortality of Trogoderma granarium (Everts), the khapra beetle, and T. inclusum (LeConte), the larger cabinet beetle. Ten 3-4 week-old larvae of either species were exposed on treated concrete arenas for 1, 2, 3, and 7 d then transferred into 175 ml diet cups containing 5 g of untreated rearing media for 30 d to evaluate delayed mortality. In a subsequent study, residual efficacy of β-cyfluthrin, deltamethrin, and chlorfenapyr was evaluated at 0–12 wks post-treatment against adults and larvae of a laboratory and a field strain of T. granarium. Ten adults or larvae of either strain were exposed on treated arenas at selected wks post-treatment and mortality was assessed after 4 and 30 d of exposure for adults and larvae, respectively. In the first study, delayed morality of T. granarium and T. inclusum larvae was <26% when exposed on arenas treated with the two pyrethroids, and T. inclusum larvae were less susceptible than T. granarium. Adult mortality was 90–100% for both strains of T. granarium across post-treatment assays regardless of insecticide treatment and there was no difference between strains. All three insecticides produced 100% mortality for the laboratory strain of T. granarium larvae in initial post-treatment assays, but then efficacy declined. Field strain larvae were more tolerant to the insecticides than laboratory strain larvae, and larvae of both T. granarium strains were more tolerant than adults. Longer exposure times were required to produce complete mortality of larvae compared to adults. All three insecticides provided residual efficacy of adults for up to three months.     

Efficacy of d-tetramethrin and acetamiprid for control of Trogoderma granarium Everts (Coleoptera: Dermestidae) adults and larvae on concrete

The khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae) is a dangerous insect of stored products that has currently expanded in Africa, Asia and Europe. Control of this species encounters difficulties when synthetic insecticides are applied either as surface treatments or as grain protectants. Therefore, new insecticidal formulations should be assessed as additional tools towards an effective management of T. granarium. In the current study, we tested the new insecticidal formulation Dobol, that contains the pyrethroid insecticide d-tetramethrin and the neonicotinoid insecticide acetamiprid, as treatments on concrete. Their direct and delayed mortality against adults and larvae of T. granarium were estimated under two label doses (min and max) and two temperature levels (30 and 35 °C) after 1, 2, 3, 4 and 7 d of exposure interval. Results revealed that Dobol caused direct mortality to T. granarium adults that ranged between 87.8 and 96.7%. Concerning larvae, direct mortality was generally much lower, being at most 84.4% at the max dose after 7 d of exposure. Temperature had significant impact on the direct mortality of T. granarium adults and larvae within the vast majority of the tested exposure intervals at both doses. However, when the surviving adults and larvae were transferred on untreated concrete surfaces, despite higher mortality at 35 than 30 °C, there was no significant impact of temperature on their mortalities within any exposure interval and dose. Our study revealed that Dobol is a promising insecticidal formulation that can be effectively used against adults and larvae of T. granarium on concrete surfaces.     

Evaluation of methoprene-treated packaging against Trogoderma granarium Everts and Trogoderma inclusum LeConte larval development and packaging penetration or invasion

Trogoderma granarium Everts, khapra beetle, and Trogoderma inclusum LeConte, larger cabinet beetle, are highly destructive insect species that can infest a variety of food sources. Methoprene is an insect growth regulator, IGR, and recently has been incorporated into packaging materials as a treatment option for packaged grain, food, birdseed, and feed products, and labeled for this use by the US Environmental Protection Agency. The objective of this research was to investigate the effect of continual exposure to this novel packaging technology on the development of T. inclusum and T. granarium larvae, and its potential use as a packaging treatment to prevent the penetration or invasion of T. inclusum and T. granarium into food packages. The methoprene-treated packaging incorporated into Kraft paper, woven bag material, polyethylene-polyethylene (PE-PE) material, and a polyethylene terephthalate-polyethylene (PET-PE) material, reduced normal adult emergence of exposed larvae. No normal adult emergence was observed on the inside surface of the PET-PE material. The polymer-based materials were the most effective at preventing penetration or invasion by Trogoderma spp. Only 2% of packages were invaded among all packaging treatment combinations compared to 16.7% invasion of untreated packages. The materials were ranked in effectiveness as Kraft < woven < PET-PE < PE-PE, however, all materials demonstrated significant positive results on Trogoderma spp. This novel packaging could easily be adopted as a packaging control strategy against these and other stored product insects in packaged products destined for commercial, international, and smallholder farm storage of cereal grains, feed, and other food products.     

Nutritional responses and digestive enzymatic profile of Trogoderma granarium Everts (Coleoptera: Dermestidae) on 10 commercial rice cultivars

The khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is an important polyphagous pest of stored grains in the world. Nutritional performance and digestive amylase and protease activity of fifth instar larvae were studied on different commercial rice cultivars (Sadri, Tarom, Neda, Fajr, Nemat, Shafagh, Kadous, Gohar, Gilane, and Khazar) at 33 ± 1 °C, relative humidity of 65 ± 5%, and a photoperiod of 14:10 (L:D) h. Larvae fed with cultivar Gilane consumed more food and increased body weight higher than those fed with other cultivars. However, the lowest values of nutritional indices were found in larvae fed with cultivar Khazar. The lightest pupal weight was on cultivars Fajr, Nemat and Sadri. The larval growth index differed from 1.99 to 2.67 on cultivars Khazar and Tarom, respectively. Among various tested cultivars, the highest standardized insect-growth index was on cultivar Gilane, whereas the lowest index was on cultivars Fajr, Nemat and Sadri. Furthermore, the fitness index showed the highest value on cultivars Gilane and Neda, and the lowest on cultivar Sadri. The amylolytic activity was the highest in larvae fed with cultivar Gilane, and the lowest in larvae fed with cultivars Fajr and Khazar. The cultivar Gilane-fed larvae exhibited the highest proteolytic activity as compared with other cultivars. The cluster analysis showed that Nemat, Neda, Fajr and Khazar were the least suitable (partially resistant) cultivars to T. granarium, which could be further investigated to identify proteins that contribute to khapra beetle resistance.     

Different diets affecting biology,physiology and cold tolerance of Trogoderma granarium Everts (Coleoptera: Dermestidae)

Biology, some physiological processes and cold hardiness of Trogoderma granarium Everts (Coleoptera: Dermestidae) on ten diets (barley, corn, millet, rice, rye, sorghum, triticale, wheat groundnut, and walnut) were studied under laboratory conditions (33 ± 1 °C with 65 ± 5% RH, 14L: 10D). According to the results, the insects reared on triticale had shortest development time, and the highest fecundity and fertility. By contrast, the longest development time, and the lowest fecundity and fertility were on groundnut. The survival rates ranged from 40 to 87% with the lowest values observed on groundnut. T. granarium larvae fed on triticale and millet had the highest amylolytic activity. In contrast, groundnut-fed larvae possessed the lowest amylolytic activity. The highest and lowest proteolytic activity was on rice and millet, respectively. Different diets had a significant effect on larval energy reserves (total body sugars, glycogen, lipid, and protein), which were at the highest levels on triticale and rye, and lowest levels on sorghum. The highest level of trehalose was on triticale, groundnut and rye, and the lowest level was on barley and sorghum. The supercooling point (SCP) of larvae reared on triticale was −20.6, which was significantly lower than on the other diets. Exposures to −5 and −10 °C/24 h were somewhat endured by larvae fed on triticale, rye, walnut, and groundnut whilst exposure to −20 °C/24 h caused 100% mortality in these food groups. These results suggest that larval food quality can affect biological and physiological characteristics and influence the supercooling point and cold hardiness of T. granarium.     

Comparative performance of the Khapra beetle,Trogoderma granarium Everts (Coleoptera: Dermestidae) on various wheat cultivars

The Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is known as a serious pest of stored grains and stored products. Host plant is an effective ecological factor on performance of an insect pest. In this study, effects of ten wheat cultivars were evaluated on life table parameters and nutritional indices of T. granarium under laboratory conditions, 33 ± 1 °C, 60 ± 5% RH and a photoperiod of 14: 10 (L: D) h. Our research showed that various wheat cultivars have significant effects on life history, demographical parameters and nutritional indices of T. granarium. The highest immature survival rate was observed on cultivar Gaskojen. Significant differences on developmental time, adult fecundity and longevity of T. granarium were found across tested wheat cultivars. In addition, there were significant differences among the wheat cultivars for population growth parameters of T. granarium. The highest (r_m) values were observed on Gaskojen (0.078 eggs/female/day) and its lower values were resulted from rearing of T. granarium on Kouhdasht and Bezostaya. The larvae fed on Gaskojen showed the higher value of food consumption as compared with others. In addition, the higher value of relative growth rate (RGR) was found on cultivar Gaskojen, while the relative lower value was observed on cultivar Kouhdasht. The results indicated that Gaskojen cultivar was a relatively susceptible wheat cultivar and Kouhdasht cultivar was relatively unsuitable host for feeding of T. granarium which could prove useful in the development of IPM programs for this pest.     

Influence of different non-grain commodities on the population growth of Trogoderma granarium Everts (Coleoptera: Dermestidae)

We investigated the population growth of the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae) on seven groups of commercially available non-grain commodities. Six powdered spices were used in the first group of experiments: black pepper, clove, nutmeg, allspice, cinnamon and turmeric. The second group of the tested commodities included seven animal products: powdered cow milk, powdered pork zelatin, sheeps’ wool, goat’s skin, ducks’ feathers, dry dog food and dry cat food. The third group of commodities was consisted of six herbs: oregano, spearmint, basil, coriander, laurel and marjoram. The fourth group of commodities contained ten pulses: chickpeas, lentil, split peas, black-eyed peas, beans, soybean flour and whole kernels, lima beans, mung bean, and broad beans. The fifth group comprised six dried fruits: Corinthian currants, sultanas, banana chips, melons, apricots and figs. The sixth group was consisted of five non-grain commodities: cottonseed cake, tobacco, black tea, Turk kahvesi and potato flour. The seventh group included seven nuts: sunflower seeds, pumpkin seeds, pistachios, roasted chickpeas (yellow), almonds, hazelnuts and walnuts. Finally, six cracked containment categories (0% cracked kernels, 5% cracked kernels and 95% intact kernels, 10% cracked kernels and 90% intact kernels, 25% cracked kernels and 75% intact kernels, 50% cracked kernels and 50% intact kernels and 100% cracked kernels) from five pulses were tested: chickpeas, black-eyed peas, mung bean, soybean and split peas. The highest progeny production (3.01 individuals per vial) was recorded on powdered cow milk. On pistachios, split peas, sunflower seeds, soybean flour, pumpkin seeds, walnuts, almonds and coriander, T. granarium built high population densities rapidly, while on roasted chickpeas, cottonseed cake, hazelnuts, chickpeas, dog food and lentils, its population growth was much less. Broad beans, melons, figs, lima beans, beans, Corinthian currants, pork zelatin and potato flour were less suitable diets for the development of this species. On black pepper, clove, nutmeg, allspice, cinnamon, turmeric, sheeps’ wool, goat’s skin, ducks’ feathers, cat food, sultanas, banana chips, apricots, tobacco, black tea, Turk kahvesi, oregano, spearmint, basil, laurel and marjoram, no progeny production was recorded. The proportion of 100% cracked black-eyed peas or mung beans was more suitable for the population growth of T. granarium. Also, the percentages of 50% cracked chickpeas or 10% cracked soybeans enhanced the development of the species, in comparison with the whole kernels of each pulse. Our study indicated that several non-grain commodities are beneficial for the population growth of T. granarium, a fact that should be seriously taken into account in international trade, as this pest may utilize them as “vehicles” of expansion.     

Efficacy of five insecticides for the control of Trogoderma granarium Everts (Coleoptera: Dermestidae) larvae on concrete

Small and large larvae of the khapra beetle, Trogoderma granarium Everts were exposed for 1, 3, and 7 d on concrete that was treated with chlorfenapyr at 0.055 mg active ingredient (a.i.)/cm² and 0.11 mg (a.i.)/cm², deltamethrin at 0.0025 mg (a.i.)/cm² and 0.005 mg (a.i.)/cm², pirimiphos-methyl at 0.025 mg (a.i.)/cm² and 0.05 mg (a.i.)/cm², pyriproxyfen at 0.000115 mg (a.i.)/cm² and 0.00023 mg (a.i.)/cm², and spinosad at 0.05 mg (a.i.)/cm² and 0.1 mg (a.i.)/cm². Then, the survived individuals were transferred on untreated concrete for 7 more days and the delayed mortality of small or large larvae was evaluated. Concerning the immediate mortality of small larvae, chlorfenapyr was the most effective among the insecticides tested causing 70% immediate mortality after 7 d of exposure at the higher dose. The other insecticides provided similar mortality levels with the exception of pyriproxyfen which was not effective, for any of the combinations tested, as mortality did not exceed 4.4%. Delayed mortality for chlorfenapyr was also high reaching 76% at 7 d of exposure at the higher dose. Pirimiphos-methyl and deltamethrin gave similar results, indicating that for these two insecticides there is also a noticeable delayed effect. For pyriproxifen and spinosad, the delayed mortality was low. Large larvae were by far more tolerant than small ones in all dose-insecticide-exposure combinations examined for both immediate and delayed mortality counts. The results of the present study show that none of the insecticides were able to totally control T. granarium larvae, illustrating the difficulties in controlling this species, with dose rates that are usually effective for other major stored product beetle species.     

Immediate and delayed effects of short exposures to phosphine on adults and larvae of the khapra beetle,Trogoderma granarium

Adults and larvae of the khapra beetle, Trogoderma granarium Everts were exposed to 3000 ppm of phosphine through the Phosphine Tolerance Test. In a first series of bioassays, observations were taken every 2 min and the exposed individuals were classified either as walking normally or as being immobilized (knocked down), i.e., not walking normally. In the second series of bioassays all individuals were exposed for 90 min to phosphine. For both bioassays delayed mortality was noted after a 7 and 14-day post exposure interval. Larvae were found to be more tolerant than adults, as the time required for the individuals to be immobilized was up to 20 min, which was almost twice as long as the time required for the immobilization of the adults. There were high levels of adult mortality 7 days later, and complete (100%) mortality 14 days after the exposure. In contrast, larval mortality was low, for both post-exposures. Adults were 100% immobilized after the termination of the 90-min exposure interval at 3000 ppm of phosphine, while the percentage of the active larvae was extremely low. Regarding the 7 days post exposure interval the percentage of larval immobilization was higher than that of adults, but this was reversed seven days later. Interestingly, development of the larvae was delayed compared to the control, after the 90 min exposure, in contrast to 20 min exposure which did not cause any delayed effect. Our work provides some first data for the evaluation of the influence of short exposures to phosphine on adults and larvae of T. granarium, which may be very useful in creating an effective initial quantification plan for the control of this species.     

Life history of Trogoderma granarium Everts (Coleoptera: Dermestidae) on peeled barley,peeled oats and triticale

The life history of the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), was investigated on cracked peeled barley, cracked peeled oats and cracked triticale. The results suggest that the biological and demographic parameters of T. granarium are affected by the tested commodities. The developmental time of total immature period of T. granarium was significantly lower on barley (35.06 days) than on oats (42.87 days) and triticale (43.58 days). Mean longevities of adult females were 7.00, 7.89 and 8.24 days, and for adult males were 5.79, 6.05 and 5.49 days when T. granarium fed on barley, oats and triticale, respectively. The highest fecundity recorded when T. granarium fed on barley (39.0 eggs/female) or triticale (35.2 eggs/female), but it was significantly lower when this species fed on oats (25.4 eggs/female). While the net reproductive rate did not differ significantly when T. granarium fed on barley (14.6 females/female), oats 10.2 (females/female) and triticale (11.0 females/female), the mean generation time was significantly lower when fed on barley (40.5 days) than on oats (48.7 days) and triticale (46.1 days). The intrinsic rate of increase of T. granarium did not differ significantly when fed on barley and triticale (0.066 and 0.052 females/female/day, respectively), but it was significantly lower when fed on oats (0.047 females/female/day). The biological and demographic parameters of T. granarium may be incorporated in population models that evaluate the population dynamics aiming to the optimization of management strategies against this noxious species.     

Population growth of the khapra beetle,Trogoderma granarium Everts (Coleoptera: Dermestidae) on different commodities

We evaluated the population growth of the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae) on different grains, cracked wheat containment categories and amylaceous materials by conducting three series of laboratory bioassays. In the first series, peeled barley, whole (raw) barley, peeled oats, whole (raw) oats, peeled rice, rough rice, rye, triticale and hard wheat were tested. In the second series, six cracked wheat containment categories were tested: wheat containing intact kernels only (0% cracked kernels), wheat containing 5% cracked kernels and 95% intact kernels, wheat containing 10% cracked kernels and 90% intact kernels, wheat containing 25% cracked kernels and 75% intact kernels, wheat containing 50% cracked kernels and 50% intact kernels and wheat containing 100% cracked kernels. In the third series, the following amylaceous commodities were tested: hard wheat (intact kernels), whole oat flakes, maize flour, whole barley flour, pasta, white soft wheat flour, whole soft wheat flour, white hard wheat flour, whole hard wheat flour, whole rye flour and semolina. Significantly more dead adults were found on wheat than on peeled barley, maize, whole oats, rough rice and rye. Significantly more larvae alive were found on wheat and triticale, than on the other grains, with the exception of oats, both whole and peeled. The increase of the percentage of cracked wheat kernels increased population growth, except in the case of 10% cracked wheat kernels. In vials that contained 100% cracked wheat kernels, 584.1 individuals per vial were found, which was 3.7 times more than the respective number of larvae alive in vials with intact wheat kernels only. Significantly more dead adults were found on whole barley flour than on the other commodities. More than 1213 larvae per vial were recorded on whole barley flour, which was 1.3–15 times higher than the other commodities. The lowest number of larvae alive was found on pasta, followed by the white soft wheat flour. The findings of the present work show that some commodities are more prone to spread T. granarium than others, a fact which should be seriously taken into account in international trade of grains and related amylaceous products.     

Efficacy and cytotoxic potential of deltamethrin,essential oils of Cymbopogon citratus and Cinnamonum camphora and their synergistic combinations against stored product pest,Trogoderma granarium (Everts)

Residual film method was followed to analyze the toxicity of deltamethrin, essential oils (EOs) of Cymbopogon citratus and Cinnamonum camphora in separate and form of various combinations against LHR1 and LHR2 populations of fifth instar larvae of Trogoderma granarium. The cytotoxic potential of LC_50s of both EOs, deltamethrin and their various combinations was as well investigated. The LHR2 population showed 23.73 fold deltamethrin resistance with respect to LHR1 population. Both EOs had high insecticidal activity than deltamethrin but C. citratus EO was less toxic than C. camphora EO against both populations. Based on strength of synergism and dose reduction index, the order of insecticidal activity of combinations in LHR1 population was: C. citratus EO: deltamethrin < C. camphora EO: deltamethrin < C. citratus EO: C. camphora EO < C. citratus EO: C. camphora EO: deltamethrin. In LHR2 population the order was: C. citratus EO: C. camphora EO < C. citratus EO: deltamethrin < C. camphora EO: deltamethrin < C. citratus EO: C. camphora EO: deltamethrin. Following to exposure of LC₅₀ of each treatment various markers of cytotoxicity viz., haemocyte viability, cell proliferation rate and mitochondrial dehydrogenase activity were decreased significantly with respect to control in both populations. Except for deltamethrin, each treatment significantly increased the lactate dehydrogenase activity. Phenoloxidase activity was reduced significantly in LHR1 population following to exposure of each treatment. Likewise, LHR2 population also showed significantly reduced activity of phenoloxidase following to exposure of each treatment except deltamethrin as it increased the activity. Furthermore, each marker of cytotoxicity was fluctuated in relation to the toxicity of LC₅₀ of treatments and combination contained both EOs and deltamethrin produced highest cytotoxicity. Findings of this study should be used in granaries for the effective control of insecticide resistance in T. granarium¹.     

Evaluation of six insecticides against adults and larvae of Trogoderma granarium Everts (Coleoptera: Dermestidae) on wheat,barley, maize and rough rice

We evaluated the following six insecticides: cypermethrin, deltamethrin, pirimiphos-methyl, silicoSec, s-methoprene and spinosad, that are registered as grain protectants, against adults or larvae of the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae) on wheat, barley, maize and rough rice. Three doses were tested: the half of the label dose, the label dose and the double label dose for each insecticide and mortality was assessed after 1, 3, 7 and 14 days (d) post exposure. For parental adults, progeny production was estimated after an additional period of 46 d of exposure. All tested insecticides were able to suppress T. granarium adults, even at the lowest dose. Pirimiphos-methyl and silicoSec were found to be most effective than the other insecticides, as these were the only ones that caused application resulted in 100% mortality at the 7-d exposure interval, at the half label or label dose. Conversely, the majority of the insecticides tested were found to be ineffective against T. granarium larvae. Pirimiphos-methyl was the only insecticide on which larval mortality reached 100% on all commodities tested and by far more effective than the other insecticides. For both adults and larvae, mortalities were generally higher on wheat and barley, than on rough rice and maize, for most of the combinations tested. Our findings indicate that the biological stage (i.e., adults or larvae) and the type of infected commodity should be seriously considered when insecticidal management strategies with cypermethrin, deltamethrin, pirimiphos-methyl, silicoSec, s-methoprene or spinosad are planned against T. granarium.     

Triple bag hermetic technology for controlling a bruchid (Spermophagus sp.) (Coleoptera,Chrysomelidae) in stored Hibiscus sabdariffa grain

We assessed the performance of hermetic triple layer Purdue Improved Crop Storage (PICS) bags for protecting Hibiscus sabdariffa grain against storage insects. The major storage pest in the grain was a bruchid, Spermophagus sp.. When we stored infested H. sabdariffa grain for six months in the woven polypropylene bags typically used by farmers, the Spermophagus population increased 33-fold over that initially present. The mean number of emergence holes per 100 seeds increased from 3.3 holes to 35.4 holes during this time period, while grain held for the same length of time in PICS bags experienced no increase in the numbers of holes. Grain weight loss in the woven control bags was 8.6% while no weight loss was observed in the PICS bags. Seed germination rates of grain held in woven bags for six months dropped significantly while germination of grain held in PICS bags did not change from the initial value. PICS bags can be used to safely store Hibiscus grain after harvest to protect against a major insect pest.     

Contributions of diet quality and diapause duration to the termination of larval diapause in khapra beetle,Trogoderma granarium (Coleoptera: Dermestidae)

Larvae of khapra beetle, Trogoderma granarium (Coleoptera: Dermestidae) have an unusual diapause during which they may sporadically feed for several years, but not complete development. Diapausing larvae have an enhanced tolerance to starvation, insecticides and extreme temperatures. Thus, knowledge of factors that terminate larval diapause may aid in the control of this pest. In the current study, we assessed the effect of diet quality (five mixtures of fresh and spent diet in a replacement series) on diapause termination for diapausing larvae from laboratory cultures aged 3, 10, or 14 months. Larvae (n = 10 replicates for each combination of diet quality and culture, 10 larvae/replicate) were held at 30 °C and observed at different intervals over the course of 188 days to record larval mortality and larval pupation (= diapause termination). Larvae were least able to survive on diets of lower quality; i.e., 88% mortality after 188 days on 0% fresh diet versus 8% mortality on 100% fresh diet (averaged across cultures). Larvae were most likely to terminate diapause on diets of higher quality; i.e., 87% termination after 188 days on 100% fresh diet versus 0% termination on 0% fresh diet (averaged across cultures). Diapausing larvae from older cultures were least likely to terminate diapause and least likely to survive. On 100% fresh diet, diapause termination of larvae from cultures aged 3, 10 and 14 months was 93, 91, and 78%, respectively. On 0% fresh diet, mortality of larvae from cultures aged 3, 10 and 14 months was 67, 97, and 100%, respectively. These results indicate that diapausing larvae can accumulate the nutrients required to terminate diapause and complete development when provided with an opportunity to do so. However, the window of opportunity continues to shrink the longer the larvae remain in diapause.     

Development of resistance in stored grain pest,Trogoderma granarium (Everts) against deltamethrin and its effective control by synergistic toxicity of bifenthrin and chlorpyrifos

The current investigation was conducted to estimate the resistance level against deltamethrin in fourth and sixth instar larvae of Trogoderma granarium collected from wheat storage warehouses of Dera Ghazi Khan (DGK), Okara (OKR) and Gujranwala (GUW). Results showed that the fourth and sixth instar larvae of collected strains warehouses moderately resistant to deltamethrin compared with the same developmental stages of insecticide susceptible laboratory strain (LAB-S). Efficacies of bifenthrin, chlorpyrifos and their various combinations were analyzed against fourth and sixth instar larvae of different strains of pest populations to minimize the development of resistance against deltamethrin. LC_50s of bifenthrin against fourth and sixth instar larvae of all the four populations were recorded at low concentrations compared to deltamethrin. The LC₅₀ values of bifenthrin against fourth instar larvae of LAB-S, DGK, OKR and GUW populations were 359.32, 416.58, 524.01 and 598.91 ppm, respectively, while these values were 204.30, 262.98, 301.89 and 355.22 ppm against sixth instar larvae of those populations, respectively. Chlorpyrifos was found to be the most effective insecticide compared to bifenthrin and deltamethrin. The LC₅₀ values of chlorpyrifos were 189.33, 305.37, 376.30 and 459.15 ppm against fourth instar larvae of LAB-S, DGK, OKR and GUW populations, respectively, whereas for sixth instar larvae those values were 98.24, 129.61, 163.43 and 230.74 ppm, respectively. Various combinations of bifenthrin and chlorpyrifos viz., 1:1, 2:1, 3:1, 1:2 and 1:3 were also tested. Based on the values of LC₅₀ and relative toxic unit, 1:3 combination was observed as the most effective among all combinations. The LC₅₀ values of fourth instar larvae of all the four populations against each insecticide and their combinations were recorded at high concentration compared to that of sixth instar larvae. Results of current investigation need to be considered in present stored grain insect pest control program of warehouses in Punjab¹.     

Identification and characterization of surface lipid components of the dried-bean beetle Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae)

The dried-bean beetle Acanthoscelides obtectus is a major post-harvest pest, which can cause up to 30% losses from dry-stored beans. For the use of microbial agents for biocontrol of A. obtectus, it is of importance to identify cuticular lipids of this pest, if we are to understand the factors responsible for preferential adhesion or selective repulsion of entomopathogenic fungi that are potentially useful for biocontrol.The cuticular lipids of adult A. obtectus of both sexes were found to consist of hydrocarbons, aldehydes, methyl- and ethyl-esters of fatty acids, triacylglycerols, free fatty acids, alcohols and sterols. All the fatty acids identified in this study were found in both ether extracts and dichloromethane extracts. The dominant fraction of all the lipids isolated from this species consisted of C_16:0, C_18:0, C_18:1, C_18:2 and C_18:3 compounds. Males and females contained similar amounts of hexadecanoic acid, but there was a significant difference between the total amounts of C_18:0, C_18:1 and C_18:2 acids in the two groups. We have also successfully identified one of the sesquiterpenes present in the cuticle as α-farnesene.