Frequent insecticide applications in cotton fields offset the positive impact of surrounding semi-natural habitats on in-field ladybeetle abundance.

Semi-natural habitats in agricultural areas play a crucial role in providing resources and shelters for insect predators. However, the impacts of local insecticide use on these beneficial effects remain poorly understood. This study examined the relationship between local insecticide intensity and the benefits of semi-natural habitats for ladybeetle populations in 38 commercial cotton fields. Ladybeetle abundance was monitored using yellow stick traps, and insecticide use was recorded. The proportion of different types of semi-natural habitats within a 2.0 km radius of each cotton field was also considered. The sampled cotton fields were classified for the frequency of their insecticide use (lower vs. higher) and the proportion of the main types of semi-natural habitats (smaller vs. larger area of grassland, woodlots, or fallow habitats) at 0.5, 1.0, 1.5, and 2.0 km. Generalized linear mixed-effects models revealed significant interactions between local insecticide intensity and coverage levels of each semi-natural habitat on ladybeetle abundance. For cotton fields with fewer grassland habitats, there were no differences in ladybeetle abundance between fields with different levels of insecticide use. In cotton fields with lower intensity of insecticide application, ladybeetle densities were markedly highest for fields within landscapes with higher level of grassland habitats. For cotton fields with higher insecticide use, there were no differences in ladybeetle abundance between fields with different levels of grassland habitats in the landscape at smaller scales (0.5, 1.0, and 1.5 km). However, at a larger scale (2 km), the numbers of ladybeetles in higher sprayed fields were lower in landscapes with a greater proportion of grassland habitats compared to landscapes with fewer grassland habitats. Our study demonstrates that the higher use of insecticides in crop fields can negates the positive effects of grassland habitats on ladybeetle density. This highlights the conflict that exists between farmers attempting to benefit from maintaining a high quality and quantity of semi-natural habitats at the landscape level versus farmer's practices that lead to the intense use of insecticides, which cause mortality to natural enemies. This study emphasizes the need for sustainable agricultural practices that balance pest control and the conservation of beneficial predator populations within agricultural landscapes. [ABSTRACT FROM AUTHOR]