Efficacy of alpha-cypermethrin and thiamethoxam against Trogoderma granarium Everts (Coleoptera: Dermestidae) and Tenebrio molitor L. (Coleoptera: Tenebrionidae) on concrete

Laboratory bioassays were conducted to evaluate alpha-cypermethrin and thiamethoxam for the control of adults, small larvae and large larvae of the khapra beetle Trogoderma granarium, and the yellow mealworm beetle Tenebrio molitor, on concrete. Factors such as dose (0.025 and 0.1 mg alpha-cypermethrin or thiamethoxam/cm²), exposure interval (1, 3 and 7 d), and formulation (alpha-cypermethrin SC and thiamethoxam WG) were evaluated. Apart from immediate assessment at end of exposure, an assessment of delayed mortality was performed with the survivors of the 7-d exposure by removing them from the treated substrate and keeping them on untreated surfaces for 7 more days. After the 7-d exposure, more T. granarium adults were dead on dishes treated with alpha-cypermethrin than with thiamethoxam. Small larvae were generally less susceptible than adults. After 7 d, small larval mortality reached 64.4% for alpha-cypermethrin, while for thiamethoxam it was <6%. Large T. granarium larvae were more tolerant than the small ones. Delayed mortality of T. granarium adults was generally high for both insecticides and doses, and ranged between 43.3 and 63.3% of those that were still alive immediately after the 7-d treatment. For both larval categories, delayed mortality was higher for larvae that had been previously exposed to alpha-cypermethrin, than with thiamethoxam. For T. molitor, after the 7-d exposure, significantly more adults were dead on dishes treated with alpha-cypermethrin than with thiamethoxam. For small larvae mortality was 38.9% at the lowest thiamethoxam dose, but in the other cases ranged between 88.9 and 95.6%. In the case of large larvae, the overall mortality was low in all tested combinations. Regarding delayed mortality of this species, it remained at low levels, for both adults and small larvae. Our results indicate that T. molitor was more susceptible than T. granarium in both insecticides tested, but alpha-cypermethrin was more effective than thiamethoxam.     

The effect of mating on the sex pheromone system of the yellow mealworm beetle,Tenebrio molitor L. (Coleoptera: Tenebrionidae)

The mating behavior of the yellow mealworm beetle (Tenebrio molitor L.) is mediated by several pheromones, including a female-produced male attractant, (R)-(+)-4-methylnonanol (4-MNol); a male-produced female attractant, (Z)-3-dodecenyl acetate; a male-produced anti-aphrodisiac; and at least one copulation pheromone. The objective of this study was to investigate the effect of mating on this complicated pheromone system. Glass rod bioassays were conducted to determine the response of virgin adult male beetles to the surface extracts of adult female beetles, prepared from virgin females, females allowed to mate once (extracted 0, 0.5, 1 or 2 h after mating), and females allowed to mate over an extended period of time (0, 1, or 21 h). Mating caused an immediate but temporary inhibition of the ability of the female extracts (FEs) to attract the males. This wore off relatively quickly, since FEs prepared 0.5–1 h after mating were as attractive as the virgin FE. Two hours after mating a second inhibition of attraction was observed, which was likely due to a drop in the titer of 4-MNol. Gas chromatographic analyses confirmed that the level of 4-MNol dropped after mating, from ∼40 ng per virgin female to below our levels of detection in mated females. A single mating event, or the 1 h extended mating, did not significantly affect the ability of the FEs to elicit copulation behavior (CB) from the males. However, FEs prepared after an extended mating (21 h) were significantly less able to attract males and to elicit CB. This is the first in depth study of the effect of a single and extended mating on sex pheromone production by a coleopteran species. In the long term, a greater understanding of the regulation of pheromone production could be useful for the manipulation of pest populations.     

Clarification of the role of 4-methylnonanol,female-produced sex pheromone of the yellow mealworm beetle,Tenebrio molitor (Coleoptera: Tenebrionidae)

The objective of this study was to clarify the role of (4R)-(+)-4-methyl-1-nonanol (MNol), a female-produced sex pheromone, in mediating the mating behavior of male Tenebrio molitor L. beetles. The abilities of MNol and authentic female extract (FE) to attract virgin males and to elicit copulatory behavior (CB) from the males were determined by bioassay. Hollow glass rods were used to mimic females. The samples of interest were assayed by coating each either on the outside or on the inside surface of the hollow rods, in order to determine if the responses were due to volatile pheromones (which would be perceived whether coated on the inside or the outside of the rods) or to “contact” pheromones (which would be perceived only when coated on the outside of the rods). The responses of virgin male beetles (6–11 days post-emergence) to FE, MNol, or pentane (control) were compared at both high and low concentrations (n = 10 for each treatment). MNol and the FE showed a similar ability to attract males, at either high or low concentrations. At high concentrations, both MNol and the FE elicited CB from the males. However, unlike the FE, at low concentrations MNol was unable to elicit CB from the males. Thus the FE must contain at least one separate “copulation pheromone” that can elicit the CB at low concentrations. Furthermore, the observed “copulation pheromone” must be volatile, since no difference in response was observed whether the FE was coated on the inside or on the outside surface of the hollow rods. Thus the biological role of MNol is likely to attract males to the females and, once the male is in the immediate vicinity of the female, to act in concert with other pheromones (of which at least one is volatile) to facilitate copulation.     

我国赤拟谷盗地理分布研究

赤拟谷盗(Tribolium castaneum(Herbst))是我国的主要储粮害虫,但近年来有关其在我国的地理分布研究少有报道。本研究采用采集、诱捕相结合的调查方法和形态鉴定方法,研究、明确了当前我国赤拟谷盗的地理分布。来自我国23个省(区)56家粮食仓储单位的调查结果显示,已在19个省(区)32家仓储单位采集到赤拟谷盗成虫;西藏4家单位、青海3家单位、甘肃省2家单位均未采集到赤拟谷盗;黑龙江省5家单位中的3家、吉林7家单位中的2家单位有极少量的赤拟谷盗。研究结果表明,赤拟谷盗在我国至少23个省(区)有分布,西藏、青海、甘肃在本调查中未见样品;在过去的60余年中,赤拟谷盗已从东南沿海个别省(区)扩散到了大部分省(区)内;建议我国进一步加强国内粮食调运过程中赤拟谷盗的防控工作,保护好储粮和生产安全。     

Food oils as kairomones for trapping Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) adults

Insect infestation in the grain-based food in storage is often reported; Tribolium castaneum is a major pest. Determination of its population size using traps is entangled with the management attempts. Pheromone traps developed for T. castaneum often use kairomones with its aggregation pheromone 4,8-dimethyldecanal (4,8 DMD). However, low trapping efficacy is reported, and the information on promising kairomones is insufficient. The objective of this research was to evaluate the performance of some locally-available food oils as kairomones, alone and in combination with the pheromone for trapping T. castaneum adults. In the first experiment, the attraction of T. castaneum adults towards different food oils, the pheromone or the commercial kairomone was tested. In the second experiment, the attraction of T. castaneum to effective food oils + pheromone was determined under laboratory condition. In the third experiment, the attraction of T. castaneum by effective food oils + pheromone was evaluated under warehouse condition. Under laboratory condition, the highest attraction of T. castaneum adults was demonstrated by mee (Madhuca longifolia) and coconut (Cocos nucifera) oils. Either of these two oils when combined with the pheromone attracted more adults than the pheromone alone. Furthermore, attraction of T. castaneum adults by the two oils separately was similar to the commercially-available combination of pheromone and the kairomone. In contrast, under warehouse condition, the combination of mee oil and pheromone attracted T. castaneum adults similar to the commercially-available combination of pheromone and the kairomone. However, the attraction by the combination of coconut oil and pheromone was lower than that, and similar to the pheromone only. This study emphasizes the potential use of food oils as kairomones to trap T. castaneum adults, and augment the efficiency of pheromone traps available for this species.     

Preference of Tribolium confusum (Coleoptera: Tenebrionidae) adults to grain patches under constant and rising temperatures

Heat treatment, an environmental friendly insect control method, has been applied to disinfest grain storage and food processing facilities. Movement of Tribolium confusum adults into grain piles (0.1, 0.5, 1.0, or 5.0 kg oat groats) was investigated at constant temperatures (30, 35, 37.5, 40, 45, or 50 °C) or rising temperatures (at a rate of 0.05 °C/min from 24 to 54 °C in laboratory, or from approximately 30 to 60 °C in a mill during a heat treatment). Adults moved among locations, paper surface, surface of grain pile and inside grain pile. There was preference for the grain at ≤37.5 °C. No single adult always stayed inside grain piles at 30 °C. At rising temperatures, adults preferred grain piles (on the surface of or inside grain piles) and moved into cold grain regardless of adult introduction methods (introduced on surface of groats piles, on paper, or premixed with groats). Rising temperatures did not drive adults out of grain piles during heat treatment.     

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.     

Toxic and antifeedant activities of potato glycoalkaloids against Trogoderma granarium (Coleoptera: Dermestidae)

The total glycoalkaloid fraction (TGA) and the two glycoalkaloids, α-chaconine and α-solanine of potato, Solanum tuberosum, were isolated. Their toxic and antifeedant activities against the Khapra beetle, Trogoderma granarium Everts were investigated. Results indicated considerable toxicity, especially when adults were topically treated with the glycoalkaloids. The TGA fraction was the most toxic with LC₅₀’s of 16.7 and 11.9 μg/mg insect, 48 and 96 h post treatment, respectively. LC₅₀’s of α-chaconine and α-solanine 96 h post treatment were 18.1 and 22.5 μg/mg insect, respectively. Moderate toxicities were recorded when insects were confined on dry-film residues of botanicals with LC₅₀’s ranging between 26.1 and 56.6, and 19.4 and 45.7, μg/cm² 48 and 96 h post treatment, respectively. Nutritional studies using the flour disc bioassay revealed significant reduction in the growth rate (RGR), food consumption rate (RCR) and food utilization (ECI) by T. granarium at concentrations ranging between 20 and 30 mg g⁻¹ food with feeding deterrent indices reaching 82.4% with the TGA fraction. When tested as binary or crude alkaloidal mixtures, toxic and antifeedant activities of glycoalkaloids were increased, indicating some additive interaction among these botanicals. There is potential for use of such compounds to protect stored grains from insect infestation.     

Development of a PC-based automatic monitoring system for Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in a rice warehouse

Flight traps were constructed and hung 6 m from the floor of a rice warehouse, with a 5 m polyvinyl chloride (PVC) tube attached to the base of each trap. The PVC tube channelled any Tribolium castaneum (Herbst) caught into a plastic specimen vial at the bottom. A pair of traps was placed at each of four designated locations in the warehouse. One of the pair of traps at each location had the vial resting on a top pan balance. The four balances were interfaced with an IBM-compatible personal computer. The signals from the balances were recorded as the weights of the insects by the computer sequentially and continually. The other trap at each location was set 1 m from the computer-controlled trap and acted as a reference trap. The insects collected from it were weighed manually on a daily basis. Trap catches using both methods were recorded for 50 days. The system was not influenced by temperature and r.h. changes, and dust fall was negligible. The weights of individual live beetles recorded monthly for 6 months did not change significantly. Thus the weights obtained during monitoring could be converted to the number of T. castaneum. A good correlation was obtained between the computer and manual trap catches, with a mean correlation coefficient of 0.898 (P < 0.001). These results demonstrate the feasibility of using a technique which monitors flight trap catches electronically and remotely.     

Demographic studies of Tribolium castaneum (Coleoptera: Tenebrionidae) on various barley cultivars

Rust-red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is one of the serious insect pests of cereal grains and other stored products throughout the world. In this research, demographic parameters of T. castaneum in response to feeding on ten barley cultivars (Behrokh, Bahman, Nosrat, Fajr 30, Makuyi, Sahra, Lout, Neek, Abidar and Sahand) were studied at 30 ± 1 °C, relative humidity of 75 ± 5% and darkness conditions. The longest larval period was on cultivars Makuyi and Fajr30, and the shortest period was on cultivar Lout. The fecundity, hatch rate, net reproductive rate, intrinsic rate of increase, and finite rate of increase was the lowest on cultivars Makuyi and Fajr30. Positive correlations were observed between the larval period, larval and pupal period, and doubling time with the grain hardness index. Moreover, there were negative correlations between the fecundity, hatch rate, R₀ and λ with the grain hardness index. The results showed that cultivars Makuyi and Fajr30 were unsuitable diets for feeding of T. castaneum, and could be suggested to be grown in areas with high potential for T. castaneum infestation.     

Effectiveness of diatomaceous earth for control of Sitophilus zeamais (Coleoptera: Curculionidae), Tribolium castaneum and Palorus subdepressus (Coleoptera: Tenebrionidae)

The effectiveness of diatomaceous earth (DE) or diatomite has been assessed against three major beetle pests of stored maize: Sitophilus zeamais (the maize weevil), Tribolium castaneum (the red flour beetle) and Palorus subdepressus (the depressed flour beetle). Maize has been treated with four doses of DE (1.5, 3, 4.5 and 6 g/kg) and four doses of Actellic Super™ Dust a chemical insecticide used as a reference (0.25, 0.5, 0.75 and 1 g/kg). The effective mortality was measured for each treatment after 1, 2, 4, 7 and 14 d of exposure. The corrected mortality rates were calculated by considering the mortality in the control group. Diatomaceous earth was as effective as Actellic Super™ Dust but required higher doses. Diatomaceous earth acted faster on S. zeamais and P. subdepressus compared to T. castaneum. The highest dose tested for DE caused the same mortality in T. castaneum as the recommended dose of Actellic Super™ Dust. Diatomaceous earth is a good alternative for the control of these three devastating insect pests of maize stocks and can readily be incorporated into integrated stored products pest management programs.     

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.     

Distribution of and association between the larger grain borer Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) and the maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) in maize stores

Interspecific interactions between the larger grain borer Prostephanus truncatus and the maize weevil Sitophilus zeamais were studied during two storage seasons in maize stores, in Bénin. Maize ears, randomly sampled from farmers’ grain stores, were ‘reared out’, i.e., kept for 4 weeks under controlled conditions for F₁ to emerge, and periodically sampled, in order to examine colonisation patterns of P. truncatus and S. zeamais. For both storage seasons, P. truncatus and S. zeamais populations were sparsely aggregated and not associated with each other. The degree and strength of association increased with each monthly sampling occasion with the Ochiai, Jaccard and Dice indices of association. By the fourth sampling occasion, P. truncatus was found on most ears and on some ears in very high numbers (>300 insects). Almost all ears with P. truncatus contained at least a few S. zeamais individuals, but many ears with S. zeamais contained no P. truncatus.     

Development of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) on sorghum milling fractions

A series of tests was conducted to determine if Tribolium castaneum (Herbst), the red flour beetle, could survive on six milled sorghum fractions: Bran, Coarse Grits, Fine Grits, Flour, Red Dogs, and Shorts. In the first test, parental adults were exposed on the fractions, removed, and then the fractions were held for six-seven weeks at 27 °C. Late instar larvae and progeny adults were present in all fractions. In the second test, at least 80% of single neonates (1-2-day-old larvae) held on 1 g of a fraction at 27 °C for seven weeks were able to complete development to the adult stage. In the final test, individual neonates were held on 1 g of a fraction at 37 °C, 32 °C, 27 °C, or 22 °C. Time to adult emergence at each temperature ranged from 17 to 23 days, 21–27 days, 28–50 days, and 67–113 days, respectively, depending on the specific fraction. Logistic functions were compared for mean developmental times for each temperature-fraction combination. The six fractions were also analyzed for ash, fat, fiber, moisture, protein, and starch content. The fractions varied with respect to these chemical constituents; fat and moisture content were negatively correlated with development in some comparisons, though overall there was no correlation between these chemical components and neonate development on the fractions. Temperature had an obvious effect on neonate development, which has implications for assessing risk of pest infestations inside sorghum mills during warmer months of the calendar year. In addition, T. castaneum will reproduce and develop on all of the sorghum fractions included in this study, which are commonly generated during the sorghum milling process. Sanitation and removal of residual materials such as the measured fractions could also help with overall pest management of T. castaneum.     

Comparison of volumetric and surface decontamination techniques for innovative processing of mealworm larvae (Tenebrio molitor)

For food and feed safety of edible insects, effective decontamination methods need to be evaluated and developed. Traditional decontamination and preparation methods were reviewed and thermal and innovative inactivation methods for the decontamination of mealworm larvae were evaluated and compared. The impact of the surface decontamination techniques direct and indirect plasma treatment, and of volumetric methods such as high hydrostatic pressure treatment (400, 500, and 600 MPa) and thermal treatments (45 °C and 90 °C) for up to 15 min on the surface microbial load and on the overall microbial count of mealworm larvae (Tenebrio molitor) have been investigated. It was found that the indirect plasma treatment was an effective means for the surface decontamination of mealworm larvae, whereas high hydrostatic pressure at 600 MPa and thermal treatments in a water bath at 90 °C in comparison resulted in the highest reduction of the overall count. It is thus concluded that volumetric methods are favorable for the inactivation of the gut microbiota of insects.Industrial relevanceEdible insects represent a valuable alternative protein source that could contribute to food and feed security and are industrially mainly unexploited. For a successful marketing of edible insects food and feed safety has to be ensured and effective decontamination methods need to be developed.     

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.     

黄粉虫幼虫粉酶解及体外抗氧化性研究

主要研究了Alcalase蛋白酶水解脱脂黄粉虫幼虫粉的工艺,并对水解产物的体外抗氧化能力进行测定.在单因素基础上以还原力为指标设计正交试验得到水解最佳条件为:温度60℃,pH值8.5,加酶量150μL,反应时间100 min.抗氧化试验结果表明,脱脂黄粉虫幼虫粉水解液清除1,1-二苯基-2-苦基苯肼(DPPH)自由基和羟自由基的半抑制率(IC_(50))分别为0.45 mg/mL和4.1 mg/mL,分别是VC的IC_(50)值的112.5倍和19.5倍,还原能力是VC的1/100.将水解前后的脱脂黄粉虫幼虫粉溶液进行高效毛细管电泳(HPCE)测定,测定结果表明,经Alcalase蛋白酶水解后,溶液中可溶性组分增多.     

Assessment of eight rice cultivars flour for feeding resistance to Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is an important pest of processed stored grains worldwide. Study of life history, feeding efficiency and digestive function of an insect on different host cultivars can indicate their resistance for the insect's population increase. Due to the economic importance of T. castaneum on stored rice flour, this research was aimed to investigate the life history, feeding indices and digestive enzymatic activity of T. castaneum on flour of eight rice cultivars (Ali-Kazemi, Dom-Siah, Fajr, Gilaneh, Gohar, Hashemi, Khazar, and Neda). A delay in the developmental time of T. castaneum was detected on cultivar Gohar. The lowest fecundity and egg fertility were observed on cultivar Gohar. Feeding indices of fourth instar larvae were the lowest on cultivars Gohar and Neda. The amylolytic activity of fourth instar larvae was the highest on cultivars Hashemi, Dom-Siah, Ali-Kazemi and Gilaneh, and the lowest on cultivar Gohar. Also, the highest and lowest proteolytic activities of fourth instar larvae were on cultivars Khazar and Hashemi, respectively. Significant correlations were detected between tested parameters of T. castaneum with starch and protein value of examined cultivars flour. The results of cluster analysis indicate that Dom-Siah, Hashemi and Ali-Kazemi are relatively susceptible cultivars, and other tested cultivars, especially Gohar, are relatively resistant cultivars for feeding of T. castaneum. The resistant rice cultivars could be further evaluated to identify secondary biochemicals that contribute to T. castaneum resistance.