Seasonal population dynamics of dusky cotton bug ( Oxycarenus spp.) in transgenic cotton varieties under field conditions.

Dusky cotton bug ( Oxycarenus spp.) has become a major insect pest for cotton crop in Pakistan. Transgenic cotton varieties provided resistance to a variety of insects pests. But, these are not safe for this emerging potential threat. In present study, nine transgenic cotton varieties (IUB-222, MNH-886, FH-142, CIM-599, A-555, CIM-602, NIAB-777, MNH - 786 and Bt- 666) were assessed for seasonal population dynamics of dusky cotton bug (DCB) under field conditions. All transgenic varieties showed a differential DCB population over the months and no transgenic variety was free from DCB population throughout the crop duration. DCB population appeared during 3rd week of July and crossed the economic threshold level (10-15 nymph/ adults or both per plant) during August. A substantial increase in DCB population was noted during September-November with its peak population during October, 2014. Among all varieties, three varieties (CIM-599, CIM-602 & IUB-222) showed a significantly lower mean population per plant (37.76, 37.87, 43.84) and two varieties (FH-142, MNH-886) gave highest population (44.71, 46.81), respectively. Correlation matrix revealed that low temperature and high humidity were promoting the DCB population. Cluster analysis revealed interesting findings that IUB-222 with least population fall in a cluster where other two varieties (FH-142 & MNH-886) possessed highest population. Moreover, two varieties (CIM-599 & CIM-602) with least population fall in second cluster regarding DCB population. These findings would be helpful for the farmers to select the varieties that showed relatively higher resistance towards DCB population and to adopt proper management strategies keeping in view the trend of DCB population during the crop season.