Effects of cereal cover crops on the main insect pests in Spanish olive orchards

In olive orchards, which are very common in the Mediterranean region, cover crops are becoming increasingly used to counter problems of erosion. Although such plant covers can provide food and shelter for beneficial insects, mites, and spiders, they may also attract pests. In order to determine their relationships with the main pests in olive orchards, an analysis was made of adult population levels and damage caused in five olive-cultivation zones, in olive orchards with cereal-crop covers and in olive orchards with conventional tillage. The effects of the cereal cover crops on insect pest populations were different and in some cases in opposite direction. Thus cereal cover crops had no impact on the different studied pests, including all those that spend part of their development cycle in the soil, such as Bactrocera oleae, Prays oleae, or Otiorrhynchus cribicollis. However, under certain conditions some pests did show an increase in abundance. Diverse trophic relationships should be investigated in this agroecosystem in future studies in order to develop appropriate crop-management policies.