Analysis of the spatial-temporal patterns of cotton bollworm population densities and their ecological determinants

Abstract

Transgenic Bt cotton has been planted in Hubei province of China since 2000. One of the main targets of Bt cotton in the region is cotton bollworm (CBW), Helicoverpa armigera, a polyphagous insect species that feeds not only on cotton but also a number of other host crops. After many years with Bt cotton planting, it is important to know how the population density of CBW has changed at the provincial level. To address the issue, we conduted a monitoring study involving 14 sample sites over 9 years from 2008 to 2016. By data analysis we found that the population density of CBW eggs on cotton plants had significant spatial and temporal differences. Temporally, the population density was significantly lower in 2015–2016 than in 2008–2014. Spatially, the population density was significantly lower in the central plain region than in the northern and southeastern mountain region. Among the six types of non-cotton host crops (i.e. wheat, maize, cole, peanuts, soybean and vegetables), wheat, maize, cole and peanuts had a positive, soybean a negative, and others no significant impact on the population density. Among the two climate factors of temperature and relative humidity, only temperature had a significant impact on the population density, where the impact was negative. The results here help understand the spatial and temporal patterns of CBW population density and their ecological determinants in the study area.