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.     

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.     

Orientation of Tribolium castaneum (Coleoptera: Tenebrionidae) adults to 4,8-dimethyldecanal,kairomone and botanical oils following ambient,low, or high temperature exposure

The aggregation pheromone 4,8-dimethyldecanal (4,8 DMD) used alone or with kairomone-baited traps generally is used for monitoringTribolium castaneum (Herbst) but low efficiency is reported. Furthermore, insect orientation to pheromones and kairomones following low or high temperature exposure is not yet understood. This research evaluated the orientation of T. castaneum adults to 4,8 DMD and common kairomones following exposure to ambient, low or high temperatures. Fifty adults were introduced to the middle of rectangular glass chamber, and movement to the treatment or control was determined after 1 h. In experiment 1, insects reared at 30°C were used. Experiments 2 and 3 used insects exposed to 10°C for 4 days (cold temperature) and 42°C for 12 h (brief high temperature), respectively at 2–8 h following cold or heat exposure. The highest trapping occurred when 4,8DMD was combined with neem oil whereas the lowest was in coconut oil alone. Neem oil alone demonstrated repellent action. Prior exposure to cold or heat initially reduced taxis of T. castaneum adults to traps. The attraction for adults exposed to cold and heat was restored after 6–8 h when traps contained pheromone + neem or coconut oil. This study marks the first to experimentally test how exposure to high or low temperatures, two key IPM tactics in the post-harvest supply chain, affects the behavioral response of an important stored-product species to pheromone- and kairomones-baited traps.     

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.     

Distance and height of attraction by walking and flying beetles to traps with simultaneous use of the aggregation pheromones from Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae)

Adults of Tribolium castaneum (Herbst) and Rhyzopertha dominica (F.) biosynthesize aggregation pheromones 4,8-dimethyldecanal and dominicalure-1/dominicalure-2, respectively. These pheromones are commonly used independently, and their simultaneous use has not been adequately studied. Furthermore, information on trapping flying R. dominica in pheromone traps is minimum. Therefore, the objectives were to evaluate distance of attraction of T. castaneum and R. dominica adults to traps having both pheromones, and height of R. dominica adult attraction to traps with its pheromone lure alone. In first experiment, both pheromones were deployed simultaneously inside a commercial pitfall trap. One-month-old 20 T. castaneum and R. dominica adults were released every 30 cm from the pheromone trap. The adults trapped were recorded at 4 and 24 h following their release. Adults of both species released were captured in higher percentages at 24 h than 4 h. At 30 cm distance, these values were 45.5% for T. castaneum and 10–12% for R. dominica for 24 h whereas they were 40.5% for T. castaneum and 5–7.5% for R. dominica following 4 h exposure. The maximum trap capture was at 30 cm for T. castaneum and 30–60 cm for R. dominica. In second experiment, a trap with two rubber septa containing dominicalure-1 and dominicalure-2 was placed at different heights inside cage, and R. dominica adults were released at the bottom. In each experiment, four replicates were tested. After 24 h, flying R. dominica adults were captured in progressively lower percentages as trap height increased up to 40 cm above the bottom of cage. Trap heights above 10 cm exhibited decreased trap capture of R. dominica compared to those at 3 cm. We conclude that simultaneous use of both aggregation pheromones better facilitates trapping of walking T. castaneum and R. dominica. Traps above 10 cm show decreased captures of flying R. dominica.     

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.     

甲酸乙酯与氮气混合熏蒸对赤拟谷盗的毒力研究

采用广口瓶密闭熏蒸法,系统研究了氮气浓度、甲酸乙酯浓度、处理时间、温度等影响因子对熏蒸效果的影响.结果表明,氮气浓度的提高可显著增加甲酸乙酯对赤拟谷盗的熏蒸效果(P＜0.05),在12μL/L的甲酸乙酯浓度下,78％的氮气浓度中,赤拟谷盗的校正死亡率为5.6％,而在95％的氮气浓度中,校正死亡率达到91.7％;不同氮气浓度下,甲酸乙酯均显示出良好的速效性,在24 h内即可发挥很好的熏蒸活性;温度对氮气和甲酸乙酯混用的熏蒸效果具有显著的影响,在所有供试温度条件下(15.0～32.5℃),低温下氮气与甲酸乙酯的熏蒸效果显著优于高温(P＜0.05);在25.0℃条件下熏蒸24 h,氮气浓度为78％、87％、90％和95％时,甲酸乙酯对赤拟谷盗的LC50分别为20.72、17.49、14.77、9.00 μL/L.     

Laboratory evaluation of development and survival of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) under constant temperatures

The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is a serious pest of stored products. The effect of temperature on the development and survival of this species was determined at five constant temperatures (20, 25, 30, 32.5 and 35 °C) in the laboratory. Results showed a temperature-dependent development of T. castaneum. Data were fitted to the nonlinear Briere model, which for the total immature period estimated the lower threshold at 20.2 °C, the upper developmental threshold at 35.3 °C, and the temperature for maximum developmental rate at 31.2 °C. The Ikemoto and Takai linear model indicated that 659.7 degree-days above a threshold of 16.9 °C were needed to complete immature development from egg to adult emergence. Survival of immature stages varied significantly across temperatures and was well described by an extreme-value function. The model indicated that the highest survival (73.0%) was estimated to occur at 27.4 °C. The curve shows a skewed bell shape, indicating that survival decreases at both ends of the temperature range. These results are useful tools for the prediction of T. castaneum phenology, as well as for its management.     

Asymmetric courtship boosts male mating success in the red flour beetle,Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Recently, the functional asymmetries of courtship and mating behavior in several major pests of economic importance at the post-harvest stages of agricultural commodities have been reported. In this study, we investigated the presence of population-level behavioral asymmetries in the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) mating pairs. Males showed left-biased population-level courtship attempts when approaching potential mates. Furthermore, no significant differences were recorded for the duration of mate recognition and copula of males approaching females from the left, right side or backside. However, precopula and whole mating duration differ significantly among males approaching females from the left, right or backside. On the other hand, lateralization of courtship attempts had a significant impact on male mating success. Left-biased courtship attempts of T. castaneum males led to a higher male mating success, as compared to right-biased and backside courtship attempts. To the best of our knowledge, this is the first study investigating the impact of side-biased courtship attempts on male mating success in T. castaneum. Moreover, our findings add basic knowledge to the mating and reproductive behavior of this important pest that damages foodstuffs worldwide, which can be useful to optimize rearing procedures of this beetle, minimizing mating success reductions due to prolonged mass-rearing. Furthermore, knowledge about the mating behavior of T. castaneum can be utilized further towards the development of traps and attractants for this pest.     

Development of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) on rice milling components and by-products: Effects of diet and temperature

Development of Tribolium castaneum (Herbst), the red flour beetle, was assessed on different rice components and their various by-products (i.e., diets) commonly found in rice mills, in two separate experiments. In the first experiment, eggs did not develop through to the adult stage on rough rice hulls, paddy rice dust, and milled rice dust, while eggs developed to the adult stage to some extent on rice flour, milled whole kernels, brown rice, milled broken kernels, and bran. For the diets where development occurred, the lowest percentage was on brown rice, and adults that emerged on brown rice had smaller elytra compared to adults emerging on the other diets. In the second experiment, 1–2-day old neonates were exposed on the diets listed above and held at 22, 27, 32, and 37 °C. At all temperatures, development to the pupal and adult stages was slowest on rice flour. At 22 °C, development to those stages took about twice as long compared to development at 27 °C. As temperature increased developmental times were reduced. Even though neonates developed slowest on rice flour adult emergence rates were not affected. Predictive models were used to estimate potential population development on the diets. At 22 and 27 °C, adult size as measured by elytra length was greatest when they developed on bran, while body weight was generally lowest for adults that developed on brown rice. Results show that T. castaneum can utilize rice components and by-products produced during the rice milling process, although not all components or by-products were optimal for development, and emphasis should be placed on cleaning and sanitation to remove food sources to limit infestations. Mill managers can use these results to show the importance of sanitation, and potentially improve overall pest management programs inside the mill.     

Comparative performance of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) across populations,resource types and structural forms of those resources

The significance of Tribolium castaneum (Herbst) as a pest of stored grains will likely be influenced by the relative availability of different resources regionally and the beetles’ ability to utilize each of them. Therefore the performance across the life cycle of laboratory and field populations of T. castaneum on commonly available structural forms of wheat and sorghum, as conventional resources, was quantified and compared to that on cotton seed. The latter is not usually associated with T. castaneum, but large beetle infestations have been recorded commonly in cotton gins in Australia. The highest number of individuals of each stage (from a given number of eggs) developed on wheat and sorghum flour and kibbled seeds. Cotton seed did not support the development of laboratory population beetles and all neonate larvae died before pupation. In contrast, some of the field population larvae did develop on cotton flour, but their number was significantly lower in comparison to development on wheat and sorghum. Field population beetles produced significantly more eggs than did laboratory population beetles, on both the whole seed and flour. Field population females had a consistently higher fecundity (～78% more eggs) than the laboratory population females, at least over the first three weeks of adult life. These results suggest that field populations of T. castaneum should be used in experiments if we are to develop a more realistic understanding of the field ecology of this species. The relative rate at which these insects infest available resources in the field also warrants further investigation.     

13种植物精油和茴香脑对赤拟谷盗成虫熏蒸活性研究

在20μL/L的剂量下,测试了13种植物精油对赤拟谷盗成虫的熏蒸作用,其中以八角茴香油效果最佳,熏蒸24 h的校正死亡率达到100%,显著高于其他精油。随着熏蒸时间的延长,八角茴香油对赤拟谷盗的LC50值逐渐降低,熏蒸12 h时LC50值为13.88μL/L,熏蒸72 h时降为5.08μL/L,仅为熏蒸12 h的0.36倍。继而采用GC-MS技术对八角茴香油的主要组分进行分离鉴定,共从八角茴香油中鉴定出21种组分,其中茴香脑的相对百分含量为79.81%,为八角茴香油的主要成分。进一步测试了茴香脑对赤拟谷盗的熏蒸毒力,熏蒸12 h时LC50值为7.76μL/L,72 h时LC50值降为3.36μL/L,不同熏蒸时段茴香脑的LC50值均低于相应时段八角茴香油的LC50值,与八角茴香油相比,茴香脑对赤拟谷盗具有更强的熏蒸作用。     

Light responses of Tribolium castaneum and Tribolium confusum (Coleoptera,Tenebrionidae): Variation with age and sex

The influence of age and sex upon the light responses of adult Tribolium castaneum and T. confusum was investigated by using light-dark alternative chambers. Males and females of both species, whether segregated by sex or in mixed groups, showed an intense photonegative response during the 2nd and 3rd days of adult life, but the response weakened considerably during the 4th and 5th days. This change in behavior is correlated with the onset of reproductive maturity. There was no significant difference in the response of 5-day-old males and females of either species, but segregated groups of T. castaneum were more photonegative than were mixed groups. Mixed groups of T. confusum were much more photonegative than mixed groups of T. castaneum, but there was no significant difference between segregated groups of the two species.     

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.     

Efficacy of atmospheric and pressurized carbon dioxide or air against Sitophilus zeamais Motchulsky (Coleoptera: Curculionidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in milled rice

Carbon dioxide gas was evaluated in the laboratory for control of Sitophilus zeamais Motchulsky and Tribolium castaneum (Herbst) in milled rice using a specially designed pressure chamber. Tests were conducted at atmospheric pressure with 60, 80 and 100% carbon dioxide and with 100% carbon dioxide pressurized to 4, 6 and 8 bars. LT₉₉ were ≤79, ≤78, and ≤148 h for all life stages of S. zeamais exposed to 60, 80 and 100% carbon dioxide, whereas, they were ≤59, ≤51 and ≤66 h for T. castaneum. Pure carbon dioxide controlled the adult stage, but there tended to be no significant differences of carbon dioxide concentrations on mortality of immature stages. When pure carbon dioxide was pressurized, mortalities of the two insect species were increased significantly. LT₉₉ values decreased with levels of applied pressure: ≤29, ≤9.0 and ≤4.8 h for S. zeamais and ≤15, ≤5.8 and ≤2.3 h for T. castaneum at pressures of 4, 6 and 8 bars, respectively. Sitophilus zeamais was more tolerant than T. castaneum to carbon dioxide gas. The adult was the most susceptible stage, however, immature stages responded differently to carbon dioxide gas applied at varying concentrations and pressure levels. Adult mortalities were lower when air was used in the pressure chamber instead of carbon dioxide. Pressurized carbon dioxide at relatively low pressure (4–8 bars) was found effective in controlling all live stages of S. zeamais and T. castaneum in milled rice with shorter exposure times than at atmospheric pressure using an inexpensive set of equipment as compared to high pressure carbon dioxide fumigation (20–30 bars).     

Damage potential of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) on cocoa beans: Effect of initial adult population density and post infestation storage time

The effect of different initial adult population densities of Tribolium castaneum (Herbst) at several post infestation storage times on the final adult population density, the percentage of damaged beans, the percentage of weight loss, and the weight of insect feeding residues on cocoa beans was investigated in laboratory experiments. Both factors interactively had highly significant (P < 0.01) effects on variables assessed. The highest mean final adult population density of 129.7 ± 4.6 was recorded in samples infested with the highest initial adult population density and stored for 150 d, while the least mean adult population density of 10.8 ± 0.54 was recorded on samples infested with the lowest initial adult population density in samples stored for 30 d. The highest percentage damaged cocoa beans 51.0 ± 1.21% was recorded in samples infested with the highest initial adult population density, while the least mean percentage damaged beans of 16.9 ± 1.26% was also recorded on samples infested with the lowest initial adult population density. Similar trends of means were recorded for all the remaining variables. Correlation between factors was significant and positive. Multiple and simple linear regressions analyses were also significant (P < 0.01) and all equations fitted the regression models and perfectly described the relationship between the independent and the dependent variables. Our results show that T. castaneum can impact negatively on both the quantity and quality of stored cocoa within just 30 days of infestation, with the impact increasing with increasing population density and post infestation storage time.