Efficacy of Iranian diatomaceous earth deposits against Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae)

Laboratory bioassays were carried out to evaluate the insecticidal efficacy of two Iranian deposits of diatomaceous earths (DEs) and a commercial formulation, SilicoSec®, against adult confused flour beetle (Tribolium confusum Jacquelin du Val). The Iranian DEs were dried and sieved to get particle sizes of 0–149, 74–149, 0–74 μm, and 0–37 μm. First, DE samples were applied at the four concentration levels of 500, 1000, 1500 and 2000 ppm and each concentration was replicated four times. Tests were carried out at 27 ± 1 °C and 55 ± 5% r.h. in continuous darkness. The beetle mortality was counted at 2, 7, and 14 days after exposure. Moreover, another experiment was conducted to estimate the LC₅₀ values of the DEs. For the first experiment, adult beetle mortality exceeded 51% when exposed for 2 d to 2000 ppm of SilicoSec®. Complete mortality was recorded at each concentration of SilicoSec® at an exposure longer than 7 days except for 500 ppm; while mortalities of T. confusum at 2000 ppm of Maragheh and Mamaghan samples with the 0–149 μm particle size were 40.62% and 85.41%, respectively. Mortality of T. confusum was influenced by concentration and time of exposure to the DEs. SilicoSec® was the most effective DE followed by Mamaghan samples. The Maragheh samples were the least effective. In addition, in most cases fractions with smaller particles were more effective than larger ones. More experiments are necessary to process natural DEs and make them commercially exploitable.     

Toxic effects of some insecticides,herbicides, and plant essential oils against Tribolium confusum Jacquelin du val (Insecta: Coleoptera: Tenebrionidae)

Cereals are staple food for many countries and are grown on millions of hectares of land, but much of the harvest is wasted due to losses by pests. To minimize these losses, many pesticides are used which are damaging to the environment and human health. There are debates to get rid of these chemicals but they are still in use at large scale. An alternative control strategy for insect pests in storage houses is the use of botanicals. In this study, four plant essential oils, two plant extracts, two herbicides, and two insecticides were used against Tribolium confusum and the comparison of toxicity was made by calculating LC₅₀ and LT₅₀ values. LC₅₀ values were higher for abamectin (2.09–10.23 mg/L) and cypermethrin (3.41–11.78 mg/L) insecticides followed by neem essential oil (7.39–19.24 mg/L) and citrus extract (10.14–24.50 mg/L). However, LC₅₀ values were maximum in case of jaman plant extract (22.38–176.42 mg/L) followed by two herbicides, Logran (19.66–39.72 mg/L) and Topik (29.09–47.67 mg/L) However, LC₅₀ values were higher for topic herbicide (24.098 ppm) and jaman essential oil (16.383 ppm) after four days of treatment. Abamectin and cypermethrin insecticides, neem essential oil and citrus plant extract also killed adults of T. confusum quicker as compared other essential oils, extracts and herbicides. Results revealed that botanical formulations being environmentally safe could be used instead of highly hazardous pesticides for stored products’ pests. This study also elaborates the non-host toxicity of herbicides commonly applied in our agroecosystem.     

Hydrocarbon Repellents Isolated from Tribolium castaneum and T. confusum (Coleoptera: Tenebrionidae)

Seven unsaturated hydrocarbons were isolated from the volatiles of two species of flour beetles, Tribolium castaneum and T. confusum, and identified as 1-pentadecene, 1-heptadecene, 1,8-heptadecadiene, 1-tetradecene, 1-hexadecene, 1,6-pentadecadiene and heptadecatriene by GLC, GLC–MS, NMR, IR and micro-ozonolysis. This is the first report of the presence of these compounds in red flour beetles, and the last four compounds are also reported for the first time in confused flour beetles. These compounds are strong repellents for the same species or each other. The roles of these compounds are discussed.     

Selection for high and low amylase activity in adult flour beetles (Tribolium confusum) (Coleoptera,Tenebrionidae)

As a result of selection for high amylase activity in two strains of the flour beetle Tribolium confusum, mean activity considerably increased. Selection for low activity was ineffective in one strain, and mean activity increased, contrary to expectation, in the downward-selection line of the other.Heritabilities of amylase activity were 0.52 and 0.18 for the two strains (estimated by offspring-midparent regression in generation 1). Environmental factors have considerable effects on activity.The outcome of selection and possible models for the genetic control of amylase activity in Tribolium are discussed.     

Influence of processing and substrate variety on survival and development of Tribolium confusum (Coleoptera: Tenebrionidae)

Tribolium confusum is a major pest of grains and grain products. Some legumes hitherto not used as major food are gaining interest due to increase in human population and the need of food and feeds. Susceptibility of fresh and processed Glycine max and Cajanus cajan flours, and white wheat flour (control) to T. confusum was studied towards effective storage techniques and cheap insect diet. Ten copulating pairs of the beetle were introduced into twenty grams of each flour. Number of eggs laid, emerged larvae, pupae, eclosed adults, and duration of development of each stage was used as indices of survival of T. confusum. Proximate composition, saponin; and α-amylase and protease inhibitors determined suitability of flours as insect diet. This work discusses the significance of proximate composition and anti-nutrient properties in fresh and roasted processed flours on the development and survival of T. confusum.     

Insecticidal effect of three diatomaceous earth formulations against adults of Sitophilus oryzae (Coleoptera: Curculionidae) and Tribolium confusum (Coleoptera: Tenebrionidae) on oat, rye, and triticale

Bioassays were conducted in the laboratory to assess the effect of the diatomaceous earth (DE) formulations Insecto, SilicoSec, and PyriSec, on stored oat, rye, and triticale, against adults of the rice weevil, Sitophilus oryzae (L.), and the confused flour beetle, Tribolium confusum Jacquelin du Val. The DEs were tested at three dose rates, 0.75, 1, and 1.5 g of DE/kg of grain. Adults of the two aforementioned species were exposed to all combinations of grain-formulation-dose rate, at 26 degrees C and 60% RH. Mortality in DE-treated commodities was recorded after 24 h, 48 h, 7 d, and 14 d of exposure for S. oryzae and T. confusum and after 21 d for T. confusum. In S. oryzae, adult mortality was almost 100% after 7 d of exposure in all three grains examined. The mortality of T. confusum adults in DE-treated grains did not reach 100%, even after 21 d of exposure. Generally, the application of DE in rye caused higher adult mortality of T. confusum than in the other two products. All three dose rates tested provided the same mortality level of S. oryzae adults after 7 d of exposure. In contrast, 1.5 g of DE resulted in significant higher adult mortality of T. confusum, in comparison with the other dose rates, even after 21 d of exposure. All formulations were equally effective after 7 d of exposure against S. oryzae, but at 48 h of exposure, PyriSec caused significantly higher mortality than the other two formulations. For both species, progeny production in the treated grains was significantly reduced in comparison with the untreated grains, whereas significant differences were noted among commodities, formulations, and dose rates. No progeny were recorded in the treated rye for either species or in the treated triticale for S. oryzae.     

Comparative insecticidal activity of different plant materials from six common plant species against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is one of the major insect pests of stored grains. Due to export legislation and zero-tolerance for live insect in trade commodities, extensive use of synthetic insecticides is in practice in order to eliminate pest infestations from the lots. Currently, the one and only acceptable chemical to be used in stored grain is phosphine but due to its excessive usage the stored grain pests are becoming resistant against it. Hence discovery of alternative compounds is much needed. In this study we have compared insecticidal efficacy of different plant materials from six commonly grown plants of Pakistan, viz. Allium sativum (Alliaceae), Zingiber officinale (Zingiberaceae), Cymbopogon citratus (Poaceae), Eucalyptus globulus (Myrtaceae), Nicotiana tabacum (Solanaceae), and Azadirachta indica (Meliaceae) against T. castaneum infesting stored wheat, rice, corn and gram pulse. Various plant parts were dried, powdered, and used as admixtures to the stored commodities in the experiments. The results have suggested that A. sativum (garlic) and Z. officinale (ginger) were more effective resulting into 15 times higher adult mortality and 4 to 5 times reduction in grain weight losses when mixed with rice grains. Similarly, A. indica when admixture with wheat checked the population growth in the resources resulting into 3.5 times less adult production compared to controls. A subsequent experiment was conducted to study the dose response of neem seed powder against the beetle pest infesting milled products. Surprisingly, better control was observed either at lowest (1% w/w) or the highest doses (5% w/w). This finding is of great interest to understand the underlying phenomenon which we assume is the ability of T. castaneum to feed selectively in flour mediums, however, further research on this aspect is required to be investigated. The results of this study support the use of botanicals for stored product pest management.     

Directional and correlated effects of selection on amylase activity,weight and developmental time in Tribolium confusum (Coleoptera,Tenebrionidae)

The interrelationships of amylase activity, weight and developmental time in a strain of Tribolium confusum were studied by selecting, in turn, for one of these traits and monitoring other, non-target characters, in all lines.Experimental lines were selected for high and low amylase activity (AH, AL), for heavy and light adult weight (WH, WL) and for fast and slow development (DF, DS). The variables monitored every generation in all lines were mean amylase activity (measured colorimetrically), mean individual adult weight, median egg-to-pupa developmental time, mean productivity (offspring per fertile pair) and % sterile pairs.The six lines may be grouped by their response to selection in a meaningful way. AH, WH, and DS all had higher amylase activity, heavier adult weight, slower development and lower fitness (lower productivity, higher percent sterility) than the corresponding AL, WL, and DF, although a different variable was under selection in each pair of lines. These results demonstrate that amylase activity, developmental time and individual weight are intercorrelated.     

Fumigant toxicity of Lavandula spica essential oil and linalool on different life stages of Tribolium confusum (Coleoptera: Tenebrionidae)

The confused flour beetle, Tribolium confusum, is a common and severe pest of stored products. Here, using fumigation tests during four different exposure times, we evaluated the toxicity of different doses of essential oil of spike lavender, Lavandula spica and one of its major constituents, linalool, on different life stages of T. confusum under laboratory conditions. The toxicity of the L. spica oil and linalool varied as a function of the developmental stage and treatment duration. Young larvae (L1) were the most susceptible to toxic effects, with LC₅₀ = 19.535 μl/L of air for L. spica oil and LC₅₀ = 14.198 μl/L of air for linalool after 24 h of exposure, whereas older larvae (L8) were affected only very little by fumigation. Linalool caused higher egg mortality than L. spica oil at equivalent doses, but lower mortality in pupae and adults. Emergence of intact adult insects from surviving eggs, larvae and pupae was further reduced as a function of dose and exposure time to both L. spica oil and linalool compared to control-treated insects. Our results show that L. spica oil and linalool might be suitable for biological control of T. confusum, but tests at a larger scale are necessary to confirm our results.     

Chemical compositions of leaf extracts from Conocarpus erectus L. (Combretaceae) and their bioactivities against Tribolium castaneum Herbst (Coleoptera: Tenebrionidae)

Botanical insecticides have long been considered as alternatives to synthetic chemical insecticides in IPM programs. Effects of aqueous and ethanolic extracts obtained from buttonwood, Conocarpus erectus L. (Combretaceae), leaves on a major kind of stored product pests, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae), were evaluated under laboratory conditions. For this purpose, LC₅₀, repellency, antifeedant properties, and some biological effects (including body weight, immature developmental time and survival) of the insect were determined. The aqueous and ethanolic extracts were highly toxic to the larvae and adults. Calculated LC₅₀ values ranged between 2.6 and 193.4 (g/kg). Both extracts had repellent and antifeedant properties against the adults. The extracts adversely affected the larval and pupal weights, developmental time, and survival. Aqueous extracts were more effective only for the LC₅₀ values and only in females. All other measured parameters do not differ between the two extracts. The bioactive properties might be related to high amounts of alkaloid, phenol and tannin. Aqueous extract of the plant leaves may be a useful alternative for chemical insecticides.     

A family of chemoreceptors in Tribolium castaneum (Tenebrionidae: Coleoptera)

Chemoperception in invertebrates is mediated by a family of G-protein-coupled receptors (GPCR). To date nothing is known about the molecular mechanisms of chemoperception in coleopteran species. Recently the genome of Tribolium castaneum was sequenced for use as a model species for the Coleoptera. Using blast searches analyses of the T. castaneum genome with previously predicted amino acid sequences of insect chemoreceptor genes, a putative chemoreceptor family consisting of 62 gustatory receptors (Grs) and 26 olfactory receptors (Ors) was identified. The receptors have seven transmembrane domains (7TMs) and all belong to the GPCR receptor family. The expression of the T. castaneum chemoreceptor genes was investigated using quantification real- time RT-PCR and in situ whole mount RT-PCR analysis in the antennae, mouth parts, and prolegs of the adults and larvae. All of the predicted TcasGrs were expressed in the labium, maxillae, and prolegs of the adults but TcasGr13, 19, 28, 47, 62, 98, and 61 were not expressed in the prolegs. The TcasOrs were localized only in the antennae and not in any of the beetles gustatory organs with one exception; the TcasOr16 (like DmelOr83b), which was localized in the antennae, labium, and prolegs of the beetles. A group of six TcasGrs that presents a lineage with the sugar receptors subfamily in Drosophila melanogaster were localized in the lacinia of the Tribolium larvae. TcasGr1, 3, and 39, presented an ortholog to CO(2) receptors in D. melanogaster and Anopheles gambiae was recorded. Low expression of almost all of the predicted chemoreceptor genes was observed in the head tissues that contain the brains and suboesophageal ganglion (SOG). These findings demonstrate the identification of a chemoreceptor family in Tribolium, which is evolutionarily related to other insect species.     

球孢白僵菌九个菌株对赤拟谷盗成虫的毒效

球孢白僵菌Beauveria bassiana (Balsamo) Vuillemin是最重要的昆虫病原真菌,广泛用于防治世界各地的多种害虫.本研究评价了球孢白僵菌9个菌株对赤拟谷盗Tribolium castaneum (Herbst)成虫的致病性.将15头赤拟谷盗成虫浸入到4个浓度(1×106,l×107,l×lo8和l×109个分生孢子/mL)的白僵菌菌株中20 s,14 d内每日记录成虫的死亡率.结果表明:IRAN 440C菌株对赤拟谷盗成虫的LC50最低(5.04 ×l07个分生孢子/mL),IRAN187C菌株的最高(5.05 ×lo8个分生孢子/mL);DEBI 005菌株对赤拟谷盗成虫的LT5o最短(2.88 d),DEBI 014菌株的最长(4.96 d).根据LC50,LT50和死亡率结果得出IRAN 440C是防治这一害虫的理想菌株.