Rhyzopertha Dominica Fabricius Research Articles

Susceptibility of wheat, Triticum vulgare (Linn.) genotypes to the lesser grain bore, Rhizopertha dominica Fabricius (Coleoptera, Bostrichidae) larvae

The lesser grain borer, Rhyzopertha dominica Fabricius (Coleoptera: Bostrichidae) is a primary pest of stored wheat. Many authors studied its development on this cereal like (e.g. wheat, rice, sorghum, oats, pearl, millet, malt, barley chickpeas, peanuts and beans etc. The aim of performed laboratory experiments was to assess the feeding preferences for the different varieties of wheat viz; HI 7747, HD 1982, K 65, Kalyan Sona, TL 174 and UPT 72294 and to evaluate their susceptibility/resistance to progeny production of R. dominica particularly larvae. The experiments were conducted at 28°C and 60 ± 5% of relative humidity. The mean survival rate of R. dominica larval and dockage in various wheat were determined. The influence of the wheat genotypes on the larval development of R. dominica was significant.The highest number of Rhizopertha dominica larvae 23.00 were present in UPT 72294 which is observed the most preferred variety. This variety differs significantly from the others. The next variety in order to preference for food is TL 174 having 10 larvae followed by H.D. 1982 having 5.66 larvae, which do not differ significantly to each other but differ significantly from the rest of the varieties. The least preferred varieties are HI 7747 and K65 having only 1.33 larvae and these do not differ from Kalyan Sona and HD 1982.

Toxicity of Four Essential Oils Against Two Insect Pests of Stored Grains, Rhyzopertha dominica (Coleoptera: Bostrychidae) and Sitophilus oryzae (Coleoptera: Curculionidae)

The biological activity of essential oils extracted from four plants of the Lamiaceae family (Lavandula angustifolia Lawrence, 1989 (= L. officinalis Linnaeus), Mentha piperita Linnaeus, 1753, Ocimum basilicum Linnaeus, 1753 and Origanum compactum Bentham) was evaluated on adults of Rhyzopertha dominica Fabricius 1792 (Coleoptera: Bostrychidae) and Sitophilus oryzae Linnaeus, 1763 (Coleoptera: Curculionidae) using fumigation and repellency tests carried out at four doses and different exposure times, under laboratory conditions. The results obtained show that the four essential oils are often more toxic to R. dominica than to S. oryzae. LC50 varied between 15.14 and 18.49 µl/l of air for R. dominica, and between 33.51 and 50.27 µl/l of air for S. oryzae. The LT50 values ranged from 8 to 27 h for R. dominica and between 161 and 601 h for S. oryzae at a concentration of 20 µl/l of air. The oil of O. basilicum caused, after 96 h of fumigation at a concentration of 20 µl/l air/20 g of durum wheat, Triticum durum, 100 % mortality rates for R. dominica and 41 ± 13.87 % for S. oryzae. Oils of O. compactum and O. basilicum were the most active against R. dominica and S. oryzae, with repellency rates of 82 % and 60.5 %, respectively.

Insecticidal activity of Salvia veneris Hedge. Essential oil against coleopteran stored product insects and Spodoptera exigua (Lepidoptera)

Salvia species are very well known for their uses as herbal tea as well as insecticidal activity of their essential oils against stored product insects. Due to their use as herbal tea, Salvia species could be considered as perfect candidates to develop safe natural insect management agents. In the scope of the present study, the essential oil of aerial parts of Salvia veneris Hedge was investigated for insecticidal activity against 3rd instar larvae of Spodoptera exigua (Hübner) (Lepidoptera), Sitophilus granarius L., S. oryzae L., Tribolium castaneum Herbst, T. confusum Jacquelin du Val, Rhyzopertha dominica Fabricius and Oryzaephilus surinamensis L. (Coleoptera). The essential oil produced 63.0% contact toxicity against the S. exigua (beet armyworm) 3rd instar larvae at 100μL/mL and concentration. Highest contact toxicity of the oil was observed at 1μL application volume (10% (v/v: oil/acetone)) and 72h duration against O. surinamensis 81.6%, S. oryzae 71.5% and S. granarius 70.0%, respectively. S. veneris oil produced the highest fumigant toxicity at 1μL/mL application volume (10% (v/v: oil/acetone)) and 48h duration against S. oryzae 100.0%, S. granarius 97.6% and O. surinamensis 90.8%, respectively. The essential oil tested on Tribolium species and R. dominica did not produced any fumigant toxicity. The acetylcholinesterase and butyrylcholinestearase inhibitory activities of the essential oil were 85.9% and 12.2%, respectively. The antimicrobial activity (minimum inhibitory concentration, MIC) of the oil was tested against the pathogens that could be found on stored products namely Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Bacillus cereus and Bacillus subtilis. The oil produced very weak activity on all of the tested microorganisms when compared with the positive controls. The essential oil composition was analyzed by gas chromatography and gas chromatography/mass spectrometry and the aerial parts of the S. veneris was characterized by 1,8-cineole 30.4%, camphor 18.4%, camphene 12.9%, α-pinene 8.2%, borneol 5.8% and β-pinene 5.0%. As a conclusion the essential oil of S. veneris produced considerable insecticidal activity against Sitophilus species as well as acetylcholinesterase inhibitory activity which points out further attention should be given to Salvia species for the development of safe natural pest management agents.

Genotoxic studies of selected plant oil extracts on Rhyzopertha dominica (Coleoptera: Bostrichidae)

This study was conducted to compare the genotoxic effects of various concentrations of plant oils from Eruca sativa (Brassicaceae), Zingiber officinale (Zingiberaceae) and Origanum majorana (Lamiaceae) to the conventional organophosphate insecticide (Chlorpyrifos) against Rhyzopertha dominica Fabricius. The R. dominica population was reared for several generations without exposure to any insecticide. Wheat grains were sterilized at 55°C for 6h in order to eliminate any hidden infestation, treated with serial dilutions of Chlorpyrifos and plant oil extracts, and subsequently fed to R. dominica for 1, 2, 3, 6 and 8 days. The results indicated that the LC50 values of oils from E. sativa, Z. officinale and O. Majorana were 0.14, 0.23 and 0.32%, respectively, after 2 days. Genetic variations in DNA fragments after treatment with LC50 and LC25 concentrations of E. sativa, Z. officinale and O. majorana were detected by RAPD-PCR analysis using five primers. The results exhibited distinct DNA polymorphisms or alterations in DNA bands. These alterations varied depending on the substance being examined. Chlorpyrifos causes the highest level of DNA alterations (based on the appearance and disappearance DNA bands) followed by E. sativa, Z. officinale and O. majorana. These results were in direct correlation with the differences in mortality rates between extracts. It could be concluded that the plant oil extracts can be used as one of the integrated pest management tools to control R. dominica in stored products, as they are safer than chemical insecticides.

Mode of inhibition of acetylcholinesterase by monoterpenoids and implications for pest control

Recent studies proved that monoterpenoids could be an alternative to synthetic insecticides against stored-product pests. For that reason, it is necessary to learn the mode of action of these monoterpenoids. Inhibition of acetylcholinesterase (AChE) activity as a possible mode of action by 8 monoterpenoids which cause high mortality of three stored-product insect pests, Sitophilus oryzae L. (Coleoptera: Curculionidae), Rhyzopertha dominica Fabricius (Coleoptera: Bostrichidae) and Cryptolestes pusillus Schönherr (Coleoptera: Cucujidae) and the role of these monoterpenoids as inhibitors were examined. Inhibition of AChE was measured by colorimetric method where a chemical reaction with enzyme acetylcholinesterase, a substrate (acetylthiocoline iodide), the Ellman's reagent and each monoterpenoid as inhibitor was carried out. The majority of monoterpenoids tested inhibited the enzyme acetylcholinesterase; fenchone, S-carvone and linalool produced the highest inhibition. Furthermore, it was observed that fenchone, γ-terpinene, geraniol and linalool showed a reversible competitive inhibition at least at the enzyme's hydrophobic active site. S-carvone, estragole and camphor produced a mixed inhibition for this enzyme binding to either the free enzyme or the enzyme–substrate complex which links to a different site from the active site where the substrate binds. No inhibition of enzyme acetylcholinesterase by E-anethole was observed.

Glucosinolate breakdown products as insect fumigants and their effect on carbon dioxide emission of insects

BackgroundGlucosinolate breakdown products are volatile, therefore good candidates for insect fumigants. However, although they are insecticidal, the mode of action of such natural products is not clear. We studied the insecticidal effect of these compounds as fumigants, and monitored the production of carbon dioxide by the insects as a probe to the understanding of their mode of action.ResultsThe fumigation 24-h LC50 against the house fly (Musca domestica L.) of allyl thiocyanate, allyl isothiocyanate, allyl cyanide, and l-cyano-2-hydroxy-3-butene was 0.1, 0.13, 3.66, and 6.2 μg cm-3, respectively; they were 0.55, 1.57, 2.8, and > 19.60 μg cm-3, respectively, against the lesser grain borer (Rhyzopertha dominica Fabricius). The fumigation toxicity of some of the glucosinolate products was very close to or better than that of the commercial insect fumigants such as chloropicrin (LC50: 0.08 and 1.3 μg cm-3 against M. domestica and R. dominica, respectively) and dichlorovos (LC50: < 0.02 and 0.29 μg cm-3 against M. domestica and R. dominica, respectively) in our laboratory tests. Significantly increased CO2 expiration was found in insects exposed to the vapor of allyl isothiocyanate, allyl thiocyanate and allyl isocyanate. Allyl isothiocyanate was also found to increase the CO2 expiration of the American cockroach (Periplaneta americana L.).ConclusionsGlucosinolate breakdown products have potential as biodegradable and safe insect fumigants. They may act on the insect respiratory system in their mode of action.

Effect of Insect Infestation and Storage on Lipids of Cereal Grains

Insect infestation of wheat, maize, and sorghum grains caused by Trogoderma granarium Everts and Rhyzopertha dominica Fabricius singly or in mixed populations resulted in substantial reductions in ...

Mineral contents of cereal grains as affected by storage and insect infestation

Insect infestation of wheat, maize and sorghum grains caused by Trogoderma granarium Everts and Rhyzopertha dominica Fabricius separately and in mixed populations resulted in substantial changes in the contents of calcium, phosphorus, zinc, iron, copper and manganese. At the highest infestation level (75%), R. dominica caused significant ( P < 0.05) increases in the mineral matter of wheat and sorghum grains owing to loss of endosperm contents, but the increase due to T. granarium damage was not significant. On the other hand, R. dominica did not significantly change the mineral content of maize but a significant ( P < 0.05) reduction was noticed at 75% infestation by T. granarium. Mixed populations of both species showed intermediate changes in the mineral contents of the three cereal grains. Storage of uninfested grains up to 4 months did not induce any appreciable changes in the levels of the six minerals. Variations in mineral content in relation to distribution in seed components and to feeding habits of insects have been discussed in the paper.