Abstract
Greenhouse experiments were conducted at Khartoum (Sudan) with the aphid predator Hippodamia variegata, two botanical and one synthetic insecticides: neem seed water extract (25 g fresh seed powder per I of water), NeemAzal T/S (R) (1 % azadirachtin A) and fenvalerate (Sumicidin (R) 20 % EC). An equivalent of 400 l/ha was applied with a plastic hand sprayer, containing 0.2 l Sumicidin (40 g/ha fenvalerate), 1.6 l NeemAzal (16 g/ha azadirachtin A) or 10 kg of neem seed powder (ca. 30 g/ha azadirachtin A was applied as neem seed water extract). The beetles were fed on Aphis gossypii reared on cucumber leaves. Four different stages of the predator were sprayed topically with the test preparations. In addition, beetles were fed on A. gossypii either topically sprayed or collected from cucumber plants, which soil was treated four days earlier. The preparations varied in their effects on the different stages of the predator. Neem weed water extract was less harmful to the predator than NeemAzal T/S. In topical treatments with NeemAzal T/S the corrected mortality (%) was: eggs 37.7, larvae 40.0, pupae 38.2, and adults 16.7; with neem seed water extract: eggs 15.1, larvae 26.7, pupae 29.4, and adults 10.0; with fenvalerate: eggs 86.8, larvae 100, pupae 73.5, and adults 100. Feeding L2 larvae and adults on contaminated aphids resulted in the following corrected mortalities (%): Sumicidin 100, NeemAzal ca. 40 and neem seed water extract 20/17 (larvae/adults). Feeding on aphids treated via the soil with neem seed water extract resulted at maximum in 26.4/16.7 % corrected mortality (larvae/adults), while no effects on the longevity of adults could be observed. So, in contrast to Sumicidin, neem preparations (being effective against pests) proved to be harmless for the beneficial beetle. The results are discussed concerning their importance for plant protection.