THE EFFECTS OF WEED STRIP-MANAGEMENT ON PESTS AND BENEFICIAL ARTHROPODS IN WINTER WHEAT FIELDS

摘要

To find out if winter wheat is infested with pests insects from sown weed strips and if beneficial arthropods enhanced by weed strips could decimate pests efficiently near them, strip-managed winter wheat fields and one field without a strip were investigated. Ar different distances from the weed strips and from the field edge, respectively, pest insects and their antagonists were registered by visual control and by sweep netting in 1993 and 1994. The dominant pest insects were cereal aphids and leaf beetles. The infestation with aphids was always very low and did not show any differences between the studied distances from the weed strip. In 1993, the cereal leaf beetles were more numerous in the field without strip than in the strip-managed ones and at the beginning of their incidence in 1994, they were significantly more numerous in the middle of the Field than close to the weed strip. Consequently, cereal crop was not more infested with pest insects near a weed strip than in the rest of the field. Predatory arthropods such as spiders, Nabidae and Dolichopodidae were found in larger numbers near the weed strips than in the middle of the Grids. However, parasitic Hymenoptera were mostly equally distributed over the whole fields. The number of aphidophagous predators was not significantly different between the studied distances in the wheat fields, bur they were often more abundant in the strip-managed fields than in tile field without a strip. There were fewer aphids per larvae of syrphids near the sown weed strips than in the middle of the fields and this predator-prey relationship was also closer and, consequently, better in the strip-managed fields than in the field without a strip. Thus, an enhancing effect of beneficial arthropods by sown weed strips on the adjacent wheat fields and a reduction of pest insects could be shown.