The influence of weeding treatments in red beet crop on species composition of aphidophagous Syrphidae in colonies of Aphis fabae Scop

anglais. The experiments were carried out in red beet crop (cv. Czerwona Kula) from 1995 to 2000. The aim of investigations was to determine the influence of mechanical weeding frequency on the species composition of aphidophagous Syrphidae in colonies of Aphis fabae Scop. in four treatments differing in ground coverage by weeds. No direct influence of weeds in red beet cultivation on species composition of aphidophagous Syrphidae in colonies of Aphis fabae Scop was observed. The dominant species occurred in all combinations. Their number depended on the number of aphids on plants, which was higher on plots maintained weed-free. The number of aphids feeding on plant was indirectly influenced by the degree of weediness, which also had influence on the occurrence of syrphid larvae. The percentage of some species (Episyrphus balteatus) was higher on plots kept weed-free while the percentage of other species belonging to genus of Sphaerophoria was higher on plots not weeded.

anglais. red beet, weeds, black bean aphid, aphidophagous Syrphidae

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103-109

2