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.     

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.     

种间竞争对四种储粮害虫种群动态的影响

在30 ℃、75 %相对湿度条件下研究种间竞争对玉米象(Sitophilus zeamais)、谷蠹(Rhizopertha domini-ca)、赤拟谷盗(Triboliumcastaneum)和锈赤扁谷盗(Cryptolestes ferrugineus)4种主要储粮害虫种群动态的影响,并对种群动态进行回归分析。结果表明,玉米象与谷蠹、赤拟谷盗与锈赤扁谷盗混合饲养种群增长均受到显著抑制,玉米象和谷蠹对赤拟谷盗和锈赤扁谷盗的种群增长具有明显的促进作用,赤拟谷盗和锈赤扁谷盗对玉米象和谷蠹的种群增长具有一定的抑制作用。回归分析结果表明玉米象种群最大增长潜能最大,锈赤扁谷盗最小,种群增长率变化规律不明显。     

Allozyme variation among Brazilian and U.S. populations ofRhyzopertha dominicaresistant to insecticides

The lesser grain borer (Rhyzopertha dominica (F.)) is an important pest of stored grain in many parts of the world (Paleartic, Ethiopian, Oriental, Australian, Neotropical, and Neartic regions) with the ability to fly long distances. These insects have been shown to be resistant to organophosphorus insecticides in several studies. Polyacrylamide gel electrophoresis was used to assess the genetic variability within and among eight Brazilian and seven United States populations of R. dominica and to determine how insecticide resistance may be spreading within both countries. Significant variation in allele frequency among populations was observed at all six polymorphic enzyme loci that were examined. The Brazilian and U.S. populations were genetically differentiated from one another; populations within the U.S. and those within Brazil were also differentiated from one another. The mean genetic similarity among the seven U.S. populations collected in a small region in northeast Kansas was smaller than that among eight Brazilian populations collected in a relatively large geographical area. These results are consistent with the resistance ratios to chlorpyriphos-methyl in R. dominica populations from Brazil and the U.S. and the information available concerning patterns of flight activity in this insect.     

Parasitism by the mite Acarophenax lacunatus on beetle pests of stored products

Recent reports of the biocontrolpotential of the mite species Acarophenaxlacunatus (Cross & Krantz) (Prostigmata:Acarophenacidae) and the lack of biologicalstudies on this regulatory agent led to thepresent study carried out under laboratoryconditions. The objective of the investigationwas to assess the host range of A. lacunatus,so far only reported as egg parasite ofRhyzopertha dominica (F.) (Coleoptera:Bostrichidae). Four Coleoptera species ofstored cereals were used: R. dominica,Tribolium castaneum (Herbst) (Tenebrionidae),Cryptolestes ferrugineus (Stephens)(Laemophloeidae) and Oryzaephilus surinamensis (L.) (Cucujidae). The highest rates of eggparasitism were observed on R. dominica and T.castaneum, leading to a significant decrease ofpopulations of both species and reduced wheatweight loss. A. lacunatus was also able toparasitize eggs of C. ferrugineus, but not ofO. surinamensis. These results indicate abroader host range of A. lacunatus thaninitially suspected and also strengthen itspossibility of use in integrated pestmanagement programs in storage environments.     

1%蛇床子素粉剂对三种储粮害虫的防效

研究1%蛇床子素粉剂在5种处理浓度下对3种储粮害虫谷蠹Rhizopertha dominica Fabricius、玉米象Sitophilus zeamai Motschulsky和赤拟谷盗Tribolium castaneum Herbst的防治效果。室内毒力测定结果表明,按有效成分0.5mg/kg(蛇床子素:粮食)浓度处理粮食,7d后,粮食中谷蠹、玉米象和赤拟谷盗的校正死亡率分别为97.78%、100%、86.70%,防治效果优于对照药剂防虫磷和谷虫净。将药剂处理4个月后的粮食进行接虫试验,15d后谷蠹和玉米象的防治效果仍可达100%,达到储粮害虫防治要求。     

石菖蒲提取物对四种储粮害虫的生物活性研究

研究了石菖蒲4种溶剂无水乙醇、丙酮、乙酸乙酯、石油醚提取物对玉米象、谷蠹、长角扁谷盗和锯谷盗4种储粮害虫的驱避作用和触杀作用。结果表明：石菖蒲4种溶剂提取物对4种试虫均有明显的驱避作用和触杀作用,处理60 h的平均驱避等级均达到Ⅲ级以上,对4种试虫的触杀死亡率均达到41.11%以上。     

蛇床子提取物对几种储粮害虫的驱避和触杀效应

研究蛇床子(Cnidium monnieri(L.)Cuss.)4种溶剂无水乙醇、丙酮、乙酸乙酯、石油醚提取物对玉米象Sitophilus zeamais(Motschulsky)、谷蠹Rhizopertha dominica(Fabricius)、锯谷盗Oryzaephilus surinamensis(L.)3种储粮害虫的驱避作用和触杀作用。结果表明:蛇床子4种溶剂的提取物对3种试虫具有一定的驱避作用和触杀作用,60 h的平均驱避等级最高达到Ⅴ级,对3种试虫的触杀死亡率最高达到100%。     

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。