The north-western Himalaya is one of the rich repositories of wheat genetic resources because of the preponderance of locally developed traditional crop varieties owing to high agro-climatic heterogeneity and local socio-cultural diversity. In the present study, 100 wheat landraces of this diversity rich region were evaluated for variability in physical parameters of seed to understand the basis of resistance against rice weevil, Sitophilus oryzae. The evaluation was based on the parameter of growth index (GI) of S. oryzae in different landraces. GI was correlated with different quantitative physical seed parameters, viz. hardness, length, width, length × width, test weight and qualitative parameter seed colour were studied to work out if these were related to resistance/susceptibility. Based on the parameter of GI, the six landraces viz. IC266831, IC266872, IC393109, IC392578, IC444217 and IC589276 were identified as resistant. Correlation coefficients between GI of S. oryzae and physical parameters of wheat landraces indicated that GI had significant positive relation with length × width (r = +0.573) and test weight (r = +0.549) indicated that small seeds confer resistance to S. oryzae. Also significant negative relation (r = −0.457) with GI of S. oryzae and seed hardness, indicated that hard seeds were relatively more resistant to S. oryzae.

The polyphagous insect Sitophilus oryzae L. (Coleoptera:Curculionidae) has a tremendous adaptability in feeding behaviour, making it a serious invasive pest of stored cereals. The present study identifies the metabolite composition of Sitophilus oryzae (S. oryzae) using Nuclear Magnetic Resonance (NMR) spectroscopy. Assignment of 1D-proton by NMR, 1H-1H COSY, 2D-TOCSY 1H-1H, had been done. Amongst the various biochemically important metabolites isoleucine, valine, leucine, β-hydroxybutyrate, lysine, glutamate, glutamine, proline, lactate, alanine, di-methylamine, α-glucose, β-glucose, choline, glycerophosphorylcholine and tyrosine are present in S. oryzae. In wheat-fed S. oryzae, the presence of threonine and the absence of lactate is observed. In rice-fed S. oryzae, however, the presence of lactate and the absence of threonine were observed. Barley-fed S. oryzae shows presence of both tyrosine and lactate. It is concluded that the pest S. oryzae has adaptability on different stored cereals and grains, depicting the presence of earlier reported metabolites. The present study aims to identify the key metabolic components and associated enzymes in Sitophilus oryzae fed on different cereals.

Perovskia abrotanoides Karel is a wild growing plant in Iran and has been used in traditional Iranian herbal medicine. The present study was conducted to investigate chemical composition and fumigant toxicity of the essential oil from P. abrotanoides against Sitophilus oryzae (L.) and Tribolium castaneum (Herbst). Dry flowering aerial parts of the plant were subjected to hydrodistillation using a modified Clevenger-type apparatus. The composition of the essential oil was analysed by gas chromatography (GC) and GC mass spectrophotometry. Twenty-four compounds representing 98.8% of total oil were identified. The predominant components in the oil were camphor (28.38%) and 1,8-cineole (23.18%). Fumigant toxicity was tested against 1- to 7-day-old adults of S. oryzae and T. castaneum with five replications at 25 ± 1 °C and 65 ± 5% relative humidity in dark conditions. The mortality was increased with concentrations of 32, 161, 322, 483 and 645 μl/l air and with exposure time from 2 to 15 h. The lowest concentration (32 μl/l air) of the oil induced 100% mortality of S. oryzae and T. castaneum after 15 and 8 h exposure, respectively. The oil at 322 μl/l air caused 100% mortality for S. oryzae and T. castaneum within 13 and 7 h exposure, respectively. At 645 μl/l air, the LT50 values (lethal time for 50% mortality) were 8 and 2.84 h for S. oryzae and T. castaneum, respectively. In the probit analysis, LC50 values (lethal concentration for 50% mortality) showed that T. castaneum (LC50 = 11.39 μl/l) was more susceptible than S. oryzae (LC50 = 18.75 μl/l). The essential oil of P. abrotanoides can play an important role in stored grain protection and reduce the need for the same, and also the risks associated with the use of synthetic insecticides.

The stored grain weevil, Sitophilus oryzae (Linnaeus), causes significant losses to maize grains in tropical countries. Despite the nutritional superiority of the quality protein maize (QPM), an important concern is the possible vulnerability of QPM genotypes to stored grain weevil infestation. In the present study, the responses of 24 QPM inbred lines, along with several non-QPM inbred lines and hybrids, were evaluated against S. oryzae under laboratory conditions. Two attributes, namely (i) % weight loss in the grains after a fixed period of incubation with the insect and (ii) the number of progeny insects (insect multiplication) generated from six pairs of adult insects, were considered. A cumulative resistance index was computed for each genotype giving equal weight to both attributes. The study revealed DMRQPM-60 and CML167 as the most resistant entries. Shaktiman-1, the released QPM hybrid in India, showed moderate resistance against the grain weevil. However, most of the elite QPM inbred lines as well as some non-QPM inbred lines and hybrids were found to be highly susceptible to the weevil infestation. To explore the possible relationship between enhanced protein quality and varying degree of kernel vitreousness and vulnerability to the grain weevil infestation, both the QPM and the non-QPM genotypes were analysed. The correlations between kernel quality traits and kernel texture with % kernel weight loss due to weevil infestation and insect multiplication were found to be non-significant, indicating possible influence of other factors, including pericarp thickness and endosperm composition, in determining the susceptibility of the QPM genotypes to S. oryzae. The study indicates that QPM genotypes are not necessarily susceptible to the stored grain weevil and identifies promising QPM genotypes with resistance to S. oryzae.

Neem (Azadirachta indica A. Juss.) has been demonstrated to reduce insect populations in stored products through its toxic and growth-disrupting and other effects on the pests. Grain movement and percussion also help to kill pests in grain. The combination of neem and grain movement on population growth and development of four insect pests is reported in this study. Dried whole neem leaves, neem leaf powder and neem seed kernel oil were combined individually with dried beans and rice in separate experiments, and subjected to varying degrees of gentle grain tumbling. The results showed that the combined treatments were more effective in reducing populations and disturbing growth and development of Acanthoscelides obtectus (Say) (Bruchidae), Sitophilusoryzae (Linnaeus) (Curculionidae), Oryzaephilus surinamensis (Linnaeus) (Silvanidae) and Cryptolestes ferrugineus (Stephens) (Cucujidae) compared to the untreated control or the neem or tumbling treatments alone. This study demonstrates the potential of a simple, effective and cheap method of protecting stored seed or food grain in small-scale storage for resource-poor farmers who do not have access to sophisticated control methods, entoleters or other mechanical devices for grain protection.

Essential oils of three genotypes of Tagetes minuta, six of Tagetes patula and 15 of Tagetes erecta were screened for potential fumigant and contact toxicity against three stored product beetle species, Callosobruchus maculatus (Fabricius), Sitophilus oryzae (Linnaeus) and Tribolium castaneum (Herbst). Genotype 1 of T. minuta (TM-1), genotype 2 of T. patula (TP-2) and genotype 13 of T. erecta (TE-13) were the most toxic. These three genotypes were then evaluated for adult toxicity, oviposition deterrence, and ovicidal and population reduction activities. Essential oils of genotypes TM-1 and TP-2 induced 100% adult mortality for all three insect species at dosages of 50,000 ppm and 500 μg/insect in fumigant and contact toxicity bioassays, respectively. Adults of C. maculatus and S. oryzae were highly susceptible to the essential oils of the three genotypes in both fumigant and contact toxicity bioassays. The essential oil of genotype TM-1 deterred oviposition in T. castaneum by 81% and suppressed its egg hatchability by 91% when applied at a dosage of 70,000 ppm on filter paper.

Thirty-five grain sorghum genotypes representing 6 variable groups (A/B-lines, R-lines, commercial varieties, germplasms, mutants and locals) were evaluated for the orientation, colonisation and oviposition responses of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), governing the antixenosis component of resistance. In free-choice tests, the orientation and colonisation responses of the weevil were identical among all the genotypes at 24 h, varied at 48 h, and differed widely by 72 h after adult release. High degrees of antixenosis for colonisation by the adult weevils were observed among all the genotypes except 2077A and 2219B, which suggests a predominant reaction to gustatory rather than visual or olfactory stimuli. One to five egg plugs per seed were oviposited, frequently near the endosperm close to the seed base. Greater levels of antixenosis for oviposition were noticed in 2077B, DJ 6514 and IS 11758 in free-choice tests, and 2219B, M 148–138, P 721 and Nizamabad (M) in no-choice tests. To the contrary, M 35–1, Swati and Lakadi showed greater susceptibility for oviposition. Significantly less damage to seed was observed on 2219A/B, 116B, IS 9487, IS 11758, CSV 8R(M) and Local Yellow. Although the differences in seed weight loss were not significant, this parameter was relatively lower in AKMS 14B and 2219B than in the other genotypes. This indicates the need to increase the levels of resistance among the parental A/B-lines in the development of hybrids, in order to ensure better protection from rice weevil infestation in stored sorghum.

l-menthol isolated from the essential oil of Mentha arvensis and seven of its acyl derivatives were tested for contact and vapour toxicity, and ovicidal and repellent activity against the storage pests Callosobruchus maculatus F., Rhyzopertha dominica F., Sitophilus oryzae L. and Tribolium castaneum Herbst. Menthyl propionate and l-menthol were highly toxic in contact assays and vapour toxicity assays respectively. l-menthol was also found to be strongly repellent (82–100% at 0.353 μg/cm2 dose) against all the insects, while menthyl acetate was highly ovicidal against T. castaneum.

Tannin extracts of two sorghum, Sorghum bicolor (L.) Moench. cultivars, BKS5 and BTX 623 were assessed for their bioactivity against the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and the angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), in whole wheat flour pellets, and against the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in whole wheat flour at three treatment levels. The number of adult progeny was reduced and number of days to emergence increased by tannins extracted from both sorghum cultivars at all treatment levels. However, the effects were not significant in all cases. In a short-term (25 days) feeding test using S.oryzae adults, the presence of sorghum tannins from cv. BKS 5 in the pellets significantly reduced feeding by the insects.

Intraspecific competition in the rice weevil, Sitophilus oryzae (L.) and the angoumois grain moth, Sitotroga cerealella (Oliv.) in grain sorghum was studied in laboratory experiments. Progeny production per female of each of the two species when reared separately, decreased as the initial parent population density increased. The number of progeny produced by Sitophilus oryzae increased to a peak, and then declined sharply with a further increase in initial parent population density, characteristic of a scramble competition. In contrast, the progeny produced by Sitotroga cerealella increased with an increase in parental density to reach a fairly constant maximum (flat topped curve), characteristic of a contest competition. It is concluded that intraspecific competition will not limit the potential of the grain moth S. cerealella of becoming a major pest of stored sorghum.

Competition between larvae of Sitophilus oryzae (L.) and Sitotroga cerealella (Oliv.) within sorghum grains was studied at 30°C and 70% r.h. Newly hatched S. cerealella larvae (0 - 24 hr) were allowed to infest single sorghum grain having one S. oryzae egg deposited either on the endosperm half or the germ half. S. cerealella larvae were obtained from eggs of the same age as those of the weevil. The moth larvae entered the grain through the germ half. When S. oryzae egg was deposited in the germ half, S. cerealella survival probability was 0.78. However, when S. oryzae egg was deposited in the endosperm half, S. cerealella survival probability was 0.47. When the data for the two sites were combined the probability that the moth larvae will survive competition (P = 0.58) was not significantly different from that of the weevil. Hence, both larvae have similar chances of surviving competition within the sorghum grain.

Local West African strains of Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) were placed in 200 g of wheat samples, one species after the other, during 6 weeks. The rate of infestation for S. oryzae was 6, 12, 24 or 48 pairs of adults, while it was fixed to 20 for T. castaneum. The generation of S. oryzae was killed by fumigation before T. castaneum infestation of the grain samples. The loss in dry weight and the frass production were recorded at the end of each rearing period of time for each species.

The dry matter loss caused by S. oryzae was highly correlated with the rate of adult infestation and measured as high as 600 mg per infesting pair of weevils. The frass production for both S. oryzae and T. castaneum was highly correlated with the rate of infestation by weevils only. For S. oryzae, the average frass production was about 60 mg per adult pair, while for T. castaneum it was variable from 27 to 44 mg per pair of the primary infestation level by the weevils.

The importance of these results is discussed in relation to standard loss assessment methods when there are several infesting species and particularly when there is a preponderance of secondary species over primary species.

Petroleum ether extract of Eichhornia crassipes (Mart) Solm. was evaluated for its biological activity against Tribolium castaneum (Herbst), Sitophilus oryzae (L.), Callosobruchus maculatiti (F.) and Corcyra cephalonica (Stainton). The crude extract included in the diet of insects retarded development and caused mortality in the fourth instar larvae of T. castaneum and C. cephalonica. Cuticle melanization in patches were observable in C. cephalonica larvae. High mortality of adult C. maculatus occurred in insects confined to the treated diet as well as in insects exposed to treated surfaces. The extract did not show any toxicity to adult S. oryzae.

Juvenile hormone analogues (JHAs), JHA I (6,7′-epoxy-3′,7′-dimethyl-dec-2′-enyl 6-ethyl-3-pyridyl ether), JHA II (3′,7′-dimethyl-undec-2,6′-dinyl 6-ethyl-3-pyridyl ether), MV-678 (2-methoxy-9-[4-isopropyl phenyl]-2, 6-dimethylnonane), and R-20458 (4-ethylphenyl-6, 7′-epoxy-geranyl ether) in acetone solution were applied to insect diets at 10ppm (v/v), and their effects on four species of stored products beetles observed. The larvae of the flour beetles, Tribolium confusum Jacquelin duVal, and Tribolium castaneum (Herbst), reared in media treated with JHAs I and II failed to pupate. At the end of the 6-week observation period, these larvae had not yet pupated. MV-678 and R-20458 produced ecdysial failures, lethal morphological abnormalities and larval/pupal and pupal/adult intermediates. Only a few apparently normal adult flour beetles emerged from these treatments. The lesser borer grain beetle, Rhizopertha dominica (Fabricus), completely failed to reproduce in a medium treated with JHA I. JHA II, MV-678 and R-20458 affected the reproduction of the two grain beetles, R. dominica and Sitophilus oryzae (L.), to varying extent, with MV-678 being the least potent JHA.

Tanzanian strains of Tribolium castaneum (Herbst), Gnatocerus maxillosus (F.), Sitophilus oryzae (L.) and Sitophilus zeamais Motschulsky were confined to maize grain treated with a dilute dust of permethrin at the rates of 1.5, 3.0 and 6.0 ppm active ingredient. The adult mortality and resulting F1 generation were recorded. G. maxillosus was very susceptible to the insecticide and even the lowest dose brought complete control. T. castaneum adults survived all treatments but few F1 were produced. Adult survival of s. oryzae and S. zeamais was progressively reduced by increasing dosage, although S. zeamais was much less susceptible to the treatment than S. oryzae.

The repellency of grain, treated with 3.0 ppm permethrin, to S. oryzae, S. zeamais and T. castaneum was tested in a simple choice chamber. Neither male nor female T. castaneum were repelled but significantly fewer eggs were laid on treated grain. For both Sitophilus spp there was no significant difference between the numbers of females or eggs observed on treated or untreated grain, but males were repelled from permethrin.

The importance of these results is discussed in relation to a recent recommendation that the treatment of shelled grain with 3.0 ppm permethrin should be adopted in Tanzania in order to control Prostephanus truncatus (Horn), a new and serious storage pest.

The use of surfactants and their blends to improve the penetration of two insect growth regulators (IGRs; hydroprene and R-20458) into wheat kernels was investigated. It was found that formulation of IGRs with a surfactant, Tween-85 (polyoxyethylene trioleate), increased mortality and/or effectiveness of the IGRs. Formulation of hydroprene with a blend of Span-80 (sorbitan monooleate) with Tween-80 (polyoxyethylene monooleate) produced results comparable to those by hydroprene with Tween-85. However, formulations of IGRs with surfactants with high or low hydrophile-lipophile balance (HLB), failed to provide suitable control of the weevil, probably due to the type of emulsions formed. The same results were obtained with hydroprene formulations with blends of Spans and Tweens, even though their HLBs were close to that of Tween-85. Residual half-life for hydroprene was about three months; formulations with Tween-85 or a blend of Span-80 did not enhance the residual activity for hydroprene in wheat.

On exposure of maize grains mixed with groundnut oil at a dose of 20 ml/kg, 100% mortality of the rice weevil, Sitophilus oryzae (L.) was observed within 24 hr and 100% at 10 and 5 ml/kg in 2 and 3 days.

Egg-laying and progeny development in the rice weevils were completely prevented at groundnut oil doses other than 1 ml/kg at which the number of eggs laid and progeny developed were 27 and 38% of those in the oil-free control during the same period. When maize treated with oil at 10–20 ml/kg was reinfested after 19 weeks with fresh adult rice weevils, less than 42% of them had died. The total number of progeny that emerged on week 23 from the two higher doses of oil was 38% of that emerging from the control.

Groudnut oil does not affect the viability of maize grains and damage after 25 weeks. Viability of maize grains was only 6–13% after oil treatment at 10–20 ml/kg compared to 100% in the untreated control.