The effect of some seed oils to Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae) in the laboratory and field conditions

In this thesis, the effect of seven different vegetable seed oils on pear psyllid Cacopsylla pyricola (Förster) eggs and nymphs as well as preventing adult females from laying eggs has been studied. For this purpose, artichoke, bitter melon, castor, flaxseed, mustard, peach, and rose hip, vegetable seed oils were used in laboratory experiments. Among these vegetable seed oils, the most effective ones, mustard, bitter melon and flax seed oils, were selected and studies were continued under field conditions. After 7 days of applications against the winter form of the pest to prevent egg-laying in the field conditions, the most effective oil was the summer oil with the oviposition deterrent rate of 79,8%. Bitter melon and mustard oil followed the summer oil with 72,5% and 68,8% deterrence rates, respectively. Flaxseed oil showed the lowest deterrence with a rate of 63,6%. Summer oil was the most effective agaisnt female oviposition with the deterrence rate of 79,8% 14 days after the applications. Mustard, bitter melon and flaxseed oil followed the summer oil with 53,2%, 50,8% and 43,4% deterrence rates, respectively. After 7 days of applications against the summer form of the pest to prevent egg-laying, the most effective oil was the summer oil with the deterrence rate of 87,7%. Mustard, bitter melon and flaxseed oil followed the summer oil with 74,7%, 68,0% and 59,6% deterrence, respectively. After 14 days of applications, summer oil deterred 82,1% of females from egg-laying followed by the mustard oil with 62,0%. Bitter melon and flaxseed oil showed 47,2% and 42,1% efficacy, respectively. To determine egg mortality rates, toxic effects of oils were assessed 7 days after the applications. The highest egg mortality rate had occurred with 90,0% in summer oil, followed by mustard oil with 76,8%. Bitter melon and flaxseed oil had a mortality rate of 69,9% and 64,7%, respectively. The toxic effect against nymphs was determined 3 days after the applications. The highest nymph mortality occurred with 90,4% in summer oil and 80,5% in 1% concentration of mustard oil. The lowest concentrations of flaxseed oil (1% and 1,5%) and 1,5% of the bitter melon had shown the lowest efficacy of 47,9%, 52,2% and 49,4%, respectively. In laboratory assays, the phytotoxicity at 1% and 1,5% oil concentrations were not at a significant level, but some vegetable oils at 2% concentration led to phytotoxicity in the leaves. Phytotoxicity was not observed at significant levels in 1% and 1,5% oil concentrations. As a result, mustard, bitter melon and flaxseed oils have been successful in preventing oviposition in both forms of this psyllid and showing toxic effects to its eggs and nymphs. For future studies, mixing oils and insecticides at certain ratios may contribute to control against this pest.