Releasing Two Important Insect Predators to Control of Aphids under Open-field and Greenhouse Conditions

Abstract

Background: Aphids are noxious and serious persistent insect pests in the open-fields and greenhouses worldwide. Many entomologists have studied the possibility of aphid control by applying ladybirds and green lacewings at different releasing rates either under open-field or under greenhouse conditions.
 Study period: All experiments were conducted within June-July 2018 in two different fields.
 Methodology: Releasing ladybird in open field and under greenhouse condition in the rates of 1:50, 1:100, and 1:200 (predator: aphid) to control aphid infestation. In addition, releasing lacewings in rates of 1:5, 1:10, and 1:20 (predator: aphid) to control aphis in open fields
 Results: The outcome data clarified that releasing 3rd instar larvae of Coccinella undecimpunctata Linnaeus at the rate of 1 larva:50 aphid was more effective than 1:100 or 1:200 rates for controlling Aphis gossypii Glover population in Okra field; achieving more than 90% reduction in the aphid population within 15 days. Under the greenhouse conditions, releasing ladybird adults at 3 successive rates (200, 100 & 50 adults) for every 150 plants induced a significant reduction in Aphis fabae Scopoli,1763 infesting soybean; gaining 89.47% reduction within 2 weeks.
 When Chrysoperla carnea Stephens 2nd instar larvae were released at rates of 1:5, 1:10, and 1:20 (predator: aphid), it was noticed that the first-rate was the most effective one, inducing 98.93% reduction in aphid’s population; while the two other rates gave less reduction. Additionally, in the case of double releases of the same species, reduction percentage at the rate of 1:5 reached 99.63%, which emphasizes that it was the most effective ratio. The other rates induced 97.05 and 95.64% reduction. Generally, a double release was more effective in all tested rates than the single one, because of the cumulative existence of the predators in large numbers at the same period of the experiment.
 Conclusion: It could be concluded that utilizing insect predators (Coccinella undecimpunctata and/or Chrysoperla carnea) at an early larval stage or C. undecimpunctata as newly emerged adults were sufficient to reduce the aphids’ populations, both under open fields and greenhouses conditions.