Insecticidal efficacy of three vegetable oils as post-harvest grain protectants of stored wheat against Rhyzopertha dominica （F.） （Coleoptera： Bostrychidae）

The lesser grain borer, Rhyzopertha dominica is a major insect pests of stored grain in the tropics. Vegetable oils （chamomile, sweet almond and coconut） at 2.5, 3.5, 5.0, 7.0 and 10.0 mL/kg were tested against Rhyzopertha dominica （F.） in wheat grain. All bioassays were conductr, d at 30℃ and 65% ＋ 2% RH. Treatments with vegetable oils at high dose （10.0 mL/kg） achieved over 95% control within 24 h of exposure to freshly treated grain, There was little difference between the three oils in their effect. Persistence of oils in grains was tested at short-term storage intervals （48, 72 and 96 h） and intermediate-term intervals （10, 20 and 30 days） after treatments. The activity of all products decreased with storage period. Seed viability was reduced by the high dose rate （10.0 mL/kg） of oil treatments. The potential use of vegetable oils as supplementary or alternative grain protectants against insect damage in traditional grain storage in developing countries is discussed.     

Effect of five diatomaceous earth formulations against Tribofium castaneum （Coleoptera： Tenebrionidae）, Oryzaephflus surinamensis （Coleoptera： Silvanidae） and Rhyzopertha dominica （Coleoptera： Bostrychidae）

Laboratory bioassays were conducted to determine the effect of food source on the survival of Tribolium castaneum Herbst, Oryzaephilus surinamensis L. and Rhyzopertha dominica F., after exposure to five diatomaceous earth （DE） formulations： Protect-It, Insecto, Perma-GuardTM, Dryacide and SilicoSec. Adults of these species were exposed to DEs at the rate of 0.5 mg/cm^2 for 1 day on filter paper inside plastic Petri dishes. After exposure, the initial mortality was counted and live individuals of the three species were held for a week in glass vials containing 50 mg wheat flour, rice and whole wheat, respectively. In the second experiment, after 1 day exposure to DEs, beetles were transferred to Petri dishes without food and held for a week to determine if the presence of food source would decrease the mortality of beetles. Experiments were carried out at 27℃ and 55% RH in the dark. The initial mortality in both of the experiments reached 100% for the three species exposed to Protect-It and in the case ofR. dominica and O. surinamensis exposed to Dryacide. In contrast, low level of mortality （〈 10%） was observed for T. castaneum exposed to Perma-GuardTM and Insecto. The mortality after the post-treatment period on food was decreased for the three species exposed to Perma-GuardTM and in the case of T. castaneum and R. dominica exposed to Insecto and SilicoSec. Adults of O. surinamensis were the most susceptible followed by R. dominica and 100% adult mortality was obtained, whereas T. castaneum were the least susceptible beetles to DEs. Protect-It and Dryacide were the most efficient DE formulations and can be used effectively in a stored grain integrated pest management program.     

Effect of growing media and their constituents on fungus gnat, Bradysia sp, nr, coprophila （Lintner） adults

This study was conducted to determine the attractiveness of two growing media, commonly utilized in greenhouses, to fungus gnat, Bradysia sp. nr. coprophila adults. The constituents of the most attractive growing medium tested were determined by gas chromatography analysis using a steam-distillation procedure. We found that fungus gnat adults were more attracted to the growing medium, SB300 Universal Professional Growing Mix, which contains composted bark, than to another growing medium （Sunshine LC1 Mix） and their components when tested in a series of laboratory experiments using multiple-choice experimental arenas. A higher percentage of fungus gnat adults were attracted to moist SB300 （92%） than SB300 growing medium that had been oven dried （8%）. In addition, fungus gnat adults preferred SB300 although they had been reared on Sunshine LC1 Mix. When comparing the SB300 fresh from the bag to growing medium that had been pasteurized and moistened with water, gas chromatographic-mass spectroscopic data showed there were declines in several terpenoid constituents as well as an increase in fatty acids and cyclosulfur. The results of this study indicate that B. sp. nr. coprophila adults prefer certain growing media, which may assist greenhouse producers in managing fungus gnats in crop production systems.     

Susceptibility of certain Egyptian and imported wheat cultivars to infestation by Sitophilus oryzae and Rhyzopertha dominica

Stored wheat grains are vulnerable to attack by Sitophilus oryzae and Rhyzopertha dominica, which deteriorate the quality of the infested commodities, depletes nutrition value and makes them unfit for human consumption. The susceptibility of two Egyptian local (MISR1 and SIDS12) and four imported wheat (Hard Australian wheat, American Hard Red Winter, American Soft Red Winter and Romanian wheat) cultivars to infestation by S. oryzae and R. dominica was investigated. The Romanian cultivar was the most susceptible at infestation level of 20 adults/250g. For the other two infestation levels (10 and 15 adults/250g), the Romanian and American (SRW) varieties showed high susceptibility to S. oryzae by 5.13 and 5.52% and 4.32 and 4.76% for both varieties, in respect. On the other hand, the infestation with R. dominica showed the minimum weight loss in Romanian wheat and unexpectedly showed maximum number of emerged adults after three months storage. Maximum means of damaged grains were recorded in Romanian and American (HRW) cultivars caused by S. oryzae and R. dominica infestations, respectively. Moreover, chemical changes were recorded in nutritional composition of the grains when they were subjected to infestation with 20 unsexed adults/250g wheat by S. oryzae and R. dominica for three months storage.     

Immediate and delayed mortality of Rhyzopertha dominica (Coleoptera: Bostrichidae) and Sitophilus oryzae (Coleoptera: Curculionidae) adults exposed to spinosad-treated commodities

A series of tests was conducted to characterize differences in the mortality of the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), and rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), exposed to three commodities treated with a liquid and dry spinosad formulation. In laboratory bioassays, adults of the two insect species were exposed to untreated wheat, Triticum aestivum L., corn, Zea mays L., and sorghum, Sorghum bicolor (L.) Moench., and to commodities treated with 1 mg (AI)/kg of liquid and dry spinosad formulations. Mortality was assessed from independent samples examined at specific time intervals to determine immediate mortality and after 24 h of recovery on untreated grain at 28 degrees C and 65% RH to determine delayed mortality. Comparison of the time required for 50% (LT50) and 95% (LT95) mortality indicated that R. dominica adults were consistently and significantly more susceptible (died quickly) than S. oryzae adults when exposed to spinosad-treated commodities. In general, the toxicity of liquid and dry spinosad formulations was similar against R. dominica or S. oryzae. The toxicity of spinosad to each species varied slightly among the three commodities, and there were no consistent trends to suggest that spinosad was more effective on one commodity versus another. LT50 values based on immediate mortality for R. dominica on all commodities ranged from 0.45 to 0.74 d; corresponding values based on delayed mortality ranged from 0.04 to 0.23 d, suggesting delayed toxic action of spinosad in R. dominica. LT50 values based on immediate and delayed mortality for S. oryzae on all three commodities treated with the two spinosad formulations were essentially similar and ranged from 2.75 to 4.56 d. LT95 values for R. dominica based on immediate mortality on spinosad-treated commodities ranged from 1.75 to 3.36 d, and those based on delayed mortality ranged from 0.49 to 1.88 d. There were no significant differences in LT95 values based on immediate and delayed mortality for S. oryzae on spinosad-treated commodities, and the LT95 values ranged from 7.62 to 18.87 d. The toxicity of spinosad was enhanced during a 24-h holding period after removal from spinosad-treated commodities only against R. dominica adults, and possible reasons for increased postexposure mortality of R. dominica adults after brief exposures to spinosad warrant further study.     

Characterization of midgut trypsin-like enzymes and three trypsinogen cDNAs from the lesser grain borer, Rhyzopertha dominica (Coleoptera: Bostrichidae)

Protein digestion in the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), results from the action of a complex of serine proteinases present in the midgut. In this study we partially characterized trypsin-like enzyme activity against N-alpha-benzoyl-L-arginine p-nitroanilide (BApNA) in midgut preparations and cloned and sequenced three cDNAs for trypsinogen-like proteins. BApNAase activity in R. dominica midgut was significantly reduced by serine proteinase inhibitors and specific inhibitors of trypsin, whereas BApNAase activity was not sensitive to specific inhibitors of chymotrypsin or aspartic proteinases. However, trans-epoxysuccinyl-L-leucylamido-(4-guanidino) butane (E-64) inhibited BApNAase activity by about 30%. BApNAase was most active in a broad pH range from about pH 7 to 9.5. The gut of R. dominica is a tubular tract approximately 2.5 mm in length. BApNAase activity was primarily located in the midgut region with about 1.5-fold more BApNAase activity in the anterior region compared to that in the posterior region. Proteinases with apparent molecular masses of 23-24 kDa that were visualized on casein zymograms following electrophoresis were inhibited by TLCK. Three cDNAs for trypsinogen-like proteins were cloned and sequenced from mRNA of R. dominica midgut. The full cDNA sequences consisted of open reading frames encoding 249, 293, and 255 amino acid residues for RdoT1, RdoT2, and RdoT3, respectively. cDNAs RdoT1, RdoT2, and RdoT3 shared 77-81% sequence identity. The three encoded trypsinogens shared 54-62% identity in their amino acid sequences and had 16-18 residues of signal peptides and 12-15 residues of activation peptides. The three predicted mature trypsin-like enzymes had molecular masses of 23.1, 28, and 23.8 kDa for RdoT1, RdoT2, and RdoT3, respectively. Typical features of these trypsin-like enzymes included the conserved N-terminal residues IVGG62-65, the catalytic amino acid triad of serine proteinase active sites (His109, Asp156, Ser257), three pairs of conserved cysteine residues for disulfide bridges, and the three residues (Asp251, Gly274, Gly284) that determine specificity in trypsin-like enzymes. In addition, RdoT2 has both a PEST-like sequence at the C-terminus and a free Cys158 near the active site, suggesting instability of this enzyme and/or sensitivity to thiol reagents. The sequences have been deposited in GenBank database (accession numbers AF130840 for RdoT1, AF130841 for RdoT2, and AF130842 for RdoT3).     

Entomopathogenic fungus as a biological control agent against Rhyzopertha dominica F. (Coleoptera: Bostrychidae) on stored wheat

To evaluate the pathogenicity of Metarhizium anisopliae (Metschinkoff) Sorokin (Deuteromycotina: Hyphomycetes) a bioassay was designed under laboratory conditions against Rhyzopertha dominica F. (Coleoptera: Bostrychidae) on stored wheat. The fungus was applied at the dose rates of 8 × 10³, 8 × 10⁵, 8 × 10⁷ and 8 × 10⁹ conidia/kg of wheat and the bioassay was conducted at 25°C with 60% relative humidity. The data regarding the mortality was recorded after 7 and 14 days exposure intervals. All the treatments gave the significant mortality of R. dominica and M. anisopliae of 8 × 10⁹ conidia/kg was found to be the most effective after a 14-day exposure interval. There was greater production of progeny when the low rate of M. anisopliae was applied to wheat. Overall, our study showed that M. anisopliae is vigorous when applied at a high dose rate which revealed an effective control of R. dominica and also played a pivotal role in the integrated pest management program (IPM) of stored wheat insect pests.     

玉米面水分含量对谷蠹生长发育和繁殖的影响

本文研究了玉米面的水分含量(21.33%、19.35%、18.67%、13.64%、10.98%)对谷蠹Rhyzopertha dominica Fabricius生长发育及产卵的影响。结果表明:玉米面的水分含量对谷蠹幼虫的发育历期影响显著,对卵和蛹的发育历期影响不显著;谷蠹卵的孵化率、幼虫和蛹的存活率在玉米面水分10.98%～19.35%的条件下增大,在玉米面水分21.33%条件下下降;谷蠹幼虫龄数也受到玉米面水分含量的影响,玉米面水分19.35%条件下幼虫龄数在3～5间变化,10.98%条件下幼虫龄数在3～8间变化;在试验的5种玉米面水分中,谷蠹只在19.35%和18.67%条件下才产卵,19.35%条件下日均产卵量和产卵期均大于18.67%条件下的相应值。     

Effect of temperature and commodity on insecticidal efficacy of spinosad dust against Sitophilus oryzae (Coleoptera: Curculionidae) and Rhyzopertha dominica (Coleoptera: Bostrychidae)

The insecticidal effect of spinosad dust, a formulation that contains 0.125% spinosad, was evaluated against adults of Sitophilus oryzae (L.) and Rhyzopertha dominica (F.) at three temperature levels (20, 25, and 30 degrees C) and four commodities (wheat, Triticum aestivum L.; barley, Hordeum vulgare L.; rice, Oryza sativa L.; and maize, Zea mays L.). For this purpose, quantities of the above-mentioned grains were treated with spinosad at two dose rates (20 and 50 ppm of the formulation, corresponding to 0.025 and 0.06 ppm AI, respectively), and mortality of the exposed adults in the treated grains was measured after 7 and 14 d, whereas progeny production was assessed 65 d later. Generally, for both species, mortality increased with dose, exposure interval, and temperature. For S. oryzae, adult survival and progeny production were lower on wheat than the other grains. After 14 d of exposure, mortality of S. oryzae adults on wheat treated with 50 ppm ranged between 61 and 98%, whereas in the other three commodities it did not exceed 42%. Mortality of R. dominica after 14 d on grains treated 50 ppm ranged between 91 and 100%. For this species, progeny production from exposed parental adults was low in all commodities regardless of temperature. Results indicate that spinosad dust can be used as an alternative to traditional grain protectants, but its effectiveness is highly determined by the target species, commodity, dose, and temperature.     

Efficacy of Bacillus thuringiensis against Lesser Grain Borer, Rhyzopertha dominica (Coleoptera: Bostrichidae)

Toxins from 36 isolates, representative of all available subspecies of Bacillus thuringiensis, were tested against larvae and adults of the lesser grain borer, Rhyzopertha dominica. beta -Exotoxin was effective against both larvae and adults. Spore-crystal complexes of subspecies darmstadiensis isolates from Germany were effective against larvae. Isolates of subspecies darmstadiensis from the US and Japan were not effective. The degree of control achieved by even the best isolate was not economically satisfactory.     

温度和寄主密度对雅脊金小蜂寄生和刺死米象幼虫的影响（英文）

本文通过研究雅脊金小蜂Theocolax elegans在6个不同温度梯度下对米象Sitophilus oryzae幼虫的寄生和取食能力,评价了雅脊金小蜂对米象的控制效果。雅脊金小蜂寄生米象的功能反应结果表明,在17℃～29℃的温度范围内,寄生蜂的寄主处理时间与温度成反比,从0.333天（17℃）到0.063天（29℃）。寄主搜索率也随温度变化而变化,17℃时最低（0.083头/天）,26℃时最高（1.521头/天）;当温度升高到29℃,寄主搜索率略有下降;但当温度升高到32℃,寄主搜索率明显下降。温度调节的功能反应模型表明,在26℃～29℃的温度范围内,寄生率较高。所以,在26℃～29℃时,雅脊金小蜂对米象有较好的控制效果。