After harvesting process, commonly insect natural enemies don't have a refugia as a shelter in field because no crops available. How to manage them and avoid moving to another places.
Insect natural enemies like parasitoids and predators need refugia, nectar and pollen to feed and alternate preys to survive after harvesting, so the key for a succesfull Conservation Biological Control strategy is to keep crop diversification. This diversification tends to increase natural enemy abundance and diversity, providing a system more resilient to pest population increase. Weed diversification and natural vegetation around the crops increase the diversity of natural enemies. Overall farming
diversity within the agroecosystem may also affect biological control by natural enemies, due in part to a wider range of flowering plants that provide nectar and pollen resources to insects during more times of the growing season. Vegetational
diversity can also provide support for insect biological control at the local and landscape levels.
The most widely known benefits of cover cropping and conservation tillage -- like erosion control and nutrient retention -- have to do with the soil. Less well known is how these practices affect natural enemies. Best regards