Flower strips as a bridge habitat facilitate the movement of predatory beetles from wheat to maize crops.

BACKGROUND Generalist predators play a key role in the biocontrol of insect pests in agricultural systems. However, predators are subject to frequent mortality events due to periodic disturbance regimes such as crop planting and harvest, which inevitably affect the population development of predators. Conservation of predators in this critical period is important for double-cropping systems such as winter wheat and summer maize, the most widely used cropping system in North China. RESULTS Planting Cnidium monnieri flower strips at field borders could not only serve as a bridge habitat to conserve the dominant predator Propylaea japonica in wheat fields during harvest but also help the predator immigrate to adjacent maize fields. The predator abundance was 7-fold higher on flower strips than that on natural vegetation strips during the wheat postharvest period and before the maize plant emergence for about a month, and its abundance in maize fields planted with flower strips was nearly 2-fold higher than that in maize fields planted with natural vegetation strips. Moreover, 77.56% of predators that entered maize fields were proven to originate from flower strips. CONCLUSION Our findings provided evidence that manipulating flower strips as a bridge habitat in wheat-maize rotation fields could conserve P. japonica during crop phenophase changes, and we quantified that the proportion of this predator in maize fields derived from flower strips. In practice, such a strategy may also be applied in other double-cropping and triple-cropping systems. This article is protected by copyright. All rights reserved.