The importance of field surrounding flora in protection of vegetable crops against pests.

摘要

In pro-ecological fields under vegetable production, biological pest control using naturally occurring enemies was of much higher importance than traditional biological control. To maintain the high level of efficacy of natural enemies against pests, the following conditions must be provided: (a) alternative prey for juvenile stages of natural enemies when pest population is still low on the crop; (b) source of pollen and nectar for adult stages of parasites; (c) and shelter and overwintering sites away from the crop. The surrounding field, defined as ecological infrastructure, has a significant role for the whole beneficial fauna within vegetable fields, including parasites and predators. Plant species present in the field surrounding provide a significant source of food (i.e. nectar or pollen for adult stages of beneficial Hymenoptera or Syrphidae), and a shelter and overwintering site for many other valuable species. Experiments carried out in many countries proved that a properly established and maintained field surrounding increases the population densities and diversity of beneficial species. The presence of predatory and parasitic insects and spiders that migrate into the crop from field margins reduces pest population. However, the increase in biodiversity alone is not always a key to effective pest control. The species composition still has a significant impact, maintaining optimum conditions for the increase in natural enemy populations.