Population density and spatial distribution pattern of Hypera postica (Coleoptera: Curculionidae) in Ardabil, Iran

The alfalfa weevil, Hypera postica (Gyllenhal), feeds almost exclusively on alfalfa, Medicago saliva L. in most region of the world where forage crop is grown. It has been investigated the population density and spatial distribution of alfalfa weevil on alfalfa in Ardabil during 2010. Using a 0.25 m(2) quadrate sample unit a reliable sample size was 65, with maximum relative variation of 15%. The relative variation (RV) of the primary sampling data was 13.6. The highest population density of the alfalfa weevil was recorded on 17(th) April. To estimate the spatial distribution pattern of this pest, data were analyzed through index of dispersion. Lloyd's mean crowding. Morisita's index and two regression models (Taylor's Power Law and Iwao's Patchiness Regression). Taylor's model showed an aggregated distribution pattern for all life stages. Iwao's patchiness regression indicated that larvae, adult and total life cycle had aggregated spatial distribution (t(c

THE SUBLETHAL EFFECTS OF FIVE COMMERCIAL INSECTICIDES ON THE AMYLOLYTIC AND PROTEOLYTIC ACTIVITY OF THE BIOCONTROL AGENT, HABROBRACON HEBETOR SAY (HYMENOPTERA: BRACONIDAE)

Habrobracon hebetor Say is an important biological control agent that has a wide range of lepidopteran hosts, especially from the Noctuidae and Pyralidae families. Nutrition is a very important element in the efficiency of natural enemies in integrated pest management (IPM). In the presented research, the sublethal effects of five selected chemical and botanical insecticides, fenvalerate, propargite, buprofezin, dayabon and palizin, on the activity of amylase and protease enzymes in the midgut of this important ectoparasitoid wasp were studied under laboratory conditions. Changes in the activity of enzymes were investigated by LC30 treatment of the female wasps, which were 0.14, 7.01, 3.04, 9.58 and   2.53 mg a.i./mL, respectively. The obtained results showed that this parasitoid wasp has a long midgut in its digestive tract. Also, there were significant differences among the enzymatic treatments (F5,12 =14.695 and 99.278) except protein concentration (F5,12 = 0.670). Regarding the amylase enzyme, the highest and lowest activities were obtained in the control and fenvalerate treatment (0.0435±0.0023 mU/mg vs. 0.0277±0.0010 mU/mg). In addition, the highest proteolytic activity was observed in the control (4.9817±0.0268 U/mg) and the lowest in the propargite treatment (3.2231±0.0917 U/mg). By closely investigating the results, dayabon and palizin showed the lowest negative effects on the enzymes and could be applied together with this parasitoid wasp in IPM designs

Laboratory toxicity and field efficacy of Lufenuron, Dinotefuran and Thiamethoxam against Hypera postica (Gyllenhal, 1813) (Coleoptera: Curculionidae)

Toxicity of the insect growth regulator lufenuron and two neonicotinoids, dinotefuran and thiamethoxam, for the alfalfa weevil, Hypera postica (Gyllenhal, 1813), was determined through exposure of the second instar larvae and adults to dipped alfalfa leaves under laboratory conditions at 25±1 °C, 60±5% RH ,16:8 L:D. Based on mode of action, the mortality of the treated larvae and adults was recorded after 72 hours for lufenuron, and after 24 hours for dinotefuran and thiamethoxam. LC50 values for second instar larvae were 34.32, 24.91.32.9, 15.82 AI L-1 and for adults were 175.67, 289.76, 164.02 AI L-1 for dinotefuran, thiamethoxam and lufenuran, respectively. Results showed that lufenuron was the most toxic to both larvae and adults of H. postica among insecticides tested. Once the height of alfalfa field reached to about 20 cm, a single treatment was made on May 11th. All insecticides reduced the mean number of alfalfa weevil. According to results of laboratory and field experiments, lufenuron might be a more valuable chemical to adequately control H. postica with little adverse effects on environment. lufenuron may be considered as alternative chemicals to other compounds with a high potential for controlling certain pests and with less adverse effects on natural enemies

Insecticidal activity of isolated essential oils from three medicinal plants on the biological control agent, Habrobracon hebetor Say - Hymenoptera : Braconidae

The effects of Allium sativum L. (Alliaceae), Piper nigrum L. (Piperaceae) and Glycyrrhiza glabra L. (Fabaceae) essential oils were investigated on the biological control agent, Habrobracon hebetor Say. The female wasps of H. hebetor were treated by LC30 concentrations of the tested essential oils for 24 h and their demography was investigated. Results indicated that the adult longevity, survival, fecundity, fertility, hatch rate, offspring sex ratio and the other demographic parameters negatively were affected by these essential oils. At the same time, our findings indicated that G. glabra essential oil has the less severe effect on H. hebetor. Accordingly, G. glabra essential oil seems to be a compatible botanical compound with H. hebetor for applying in integrated pest management programs