Muneer Abbas

Dusky Cotton Bug Oxycarenus spp. (Hemiptera: Lygaeidae): Hibernating Sites and Management by using Plant Extracts under Laboratory Conditions

Abstract The dusky cotton bug, Oxycarenus spp., has now attained the status of a major pest of cotton crops that affects lint as well as the seed quality of cotton. Surveys were conducted to explore the hibernating sites in the districts Faisalabad, Multan and Bahawalpur. The efficacies of six different plant extracts, i.e. Neem (Azadirachta indica), Milkweed (Calotropis procera), Moringa (Moringa oleifera), Citrus (Citrus sinensis), Tobacco (Nicotiana tobacum) and Castor (Ricinus communis) were tested by using three different concentrations of each plant extract, i.e. 5, 2.5 and 1.5% under laboratory conditions at 25±2°C and 70±5% RH. The data were recorded 24, 48, 72 and 96 hours after treatment application. However, Psidium guajava, Azadirachta indica, Eucalyptus camaldulensis and Mangifera indica were graded as host plants heavily infested by Oxycarenus spp. Results (α≤0.05) indicated that increasing the concentration of extracts also increased the mortality. Nicotiana tobacum and Calotropis procera respectively displayed maximum 72 and 71, 84 and 80, 97 and 89% mortality at all concentrations, i.e. 1.25, 2.50 and 5.00%, after 96 hours of application. Two concentrations (2.5 and 5%) are the most suitable for obtaining significant control of the dusky cotton bug.

Insecticide Resistance in Field Populations of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Abstract  Helicoverpa armigera (Hubner) is a notorious pest of various field crops. A contributing factor in its pest status is the development of resistance to insecticides, making the insect difficult to control. The objective of this study was to assess the toxicity of selected insecticides against natural populations of H. armigera in Pakistan and thus identify possible levels of insecticide resistance. Insects were collected from three locations in the province of Punjab, Pakistan, in three consecutive years. The median lethal concentration (LC50) of selected insecticides was determined for each field population as well as a susceptible lab strain designated as Lab-PK. Resistance ratios (RRs) for each insecticide were calculated as the ratios of the LC50 for each field population relative to that of the Lab-PK strain. Based on the calculated RRs, the field populations tested were highly resistant to bifenthrin (RR = 34.1 to 48.0), moderately to highly resistant to lambda-cyhalothrin (RR = 19.6 to 68....