How to compose an attractive agroecosystem for natural enemies

Agroecosystems are disturbed environments; consequently, many natural enemies are unable to establish stable populations within the crop fields. These disturbances are accentuated in the desert agroecosystem where the annual crop fields are ephemeral islands of productivity. Therefore, alternative, non-crop habitats may have an important role in maintaining sustainable populations of natural enemies in the desert agroecosystem. These habitats may serve as a refuge, reproduction site or alternative source for food between the crop seasons and they may be a source of natural enemies that disperse into the crop fields. Understanding the dynamics of spider populations in the different habitat types in the desert agroecosystem may enable us to compose an agroecosystem that attracts more spiders into the crop fields. In our study we investigated whether spiders, which are known to be natural enemies, invade the fields from the surrounding non-agricultural environment (semi-desert and planted trees habitats) or whether they engage in “crop-hopping” throughout the year. We also examined whether the common spiders in the crop fields use the alternative habitats for reproduction site or refuge between the crop seasons. We found that the natural semi-desert environment is a source for most of the spider species that disperse into wheat fields. Trees planted near fields also serve as refuge and reproduction sites for some species between the crop seasons. This habitat may provide refuge from harsh environmental conditions during the summer, when both the agricultural habitat and the natural environment are dry. Combining patches of natural semi-desert and planted tree habitats may increase the abundance of spiders in the crop fields.