How to compose an attractive agroecosystem for natural enemies?

Background/Question/Methods

Agroecosystems are disturbed environments that decrease the ability of natural enemies to establish stable populations within the crop fields. These disturbances are emphasized in the desert agroecosystem where the annual crop fields are short-lived islands of productivity. Therefore, it may be that alternative (non-crop) habitats 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 between the different habitat types in the desert agroecosystm may allow us to compose an agroecosystem that attract more spiders into the crop fields. In our study we tested whether spiders, which are known to be natural enemies, invade the fields from the surrounding non-agricultural environment (open natural and planted trees habitats) or whether they engage in “crop-hopping” throughout the year. We also exemined whether the common spiders in the crop fields use the alternative habitats for reproduction site or refuge between the crop seasons.

Results/Conclusions

We found that the natural semi-desert environment is a source for most of the spider species that disperse into the wheat fields. Planted trees near crop fields also serve as refuge and reproduction sites 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.