Natural possibilities of controlling leaf aphids in sunflowers
1990
Katona, A. (Somogy Megyei Novenyegeszsegugyi es Talajvedelmi Allomas, Kaposvar (Hungary))
On June 10, 1989 a 100 o/o aphid infection was observed on a 350 ha sunflower field. Examinations on samples consisting of 10 plants each showed the mean aphid number to be around or in excess of 2500 per plant. On each plant one or two clusters of ladybird eggs, each containing 21-30 eggs, were also found. The ladybird larvae began to emerge on June 13. These larvae are voracious esters, destroying an average of 80-100 aphids a day. Although no insecticidal treatment was carried out on this sunflower field, no live aphids were found in a survey carried out on July 25. On another field 1.5 km away, where the individual density of aphids and ladybirds was similar, spraying with Decis 2.5 EC /0.5 l/ha/ was carried out on June 17. The aphid control efficiency was less than 85 o/o, but the ladybird larvae were completely destroyed. Live aphid colonies were later found protected by the buds. On the two farms the soil type, cultivation method and variety cultivated were identical, as was the yield /2.2 t/ha/.
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