Evaluation of predator and prey preference of Orius niger (Wolff) (Hemiptera: Anthocoridae) in the control of important sucking pests of oilseeds

Whiteflies and thrips are important pests that active in cotton fields and in addition to direct damage, they alsoindirectly reduce quantity and quality of oilseeds. Orius niger (Wolff) (Hem.: Anthocoridae) is one of theoptimal biocontrol agents for thrips and whiteflies, which is abundant in oilseed fields, especially cotton fields ofGolestan province. In order to evaluate the predatory efficiency of O. niger, this insect was collected from cottonfields and grown in laboratory conditions. In experiments related to the study of predatory; for each predator(female), whitefly densities of 5, 10, 20, 30 and 40 nymphs, 5, 10, 20, 30 and 50 eggs and 5, 10, 20, 30 and 40thrips nymphs were placed in the Petri dish. The results of logistic regression showed that the functionalresponse model is type III for both egg and nymph stages of whitefly and type II for nymphs of thrips. For thripsnymphs, eggs and nymphs of whitefly, according to Roger's equation, calculated searching efficiency parameter(a′) was 0.0697, 0.01193 and 0.01072 /h, and handling time (Th) was 0.3802, 0.2686 and 4.1042 hours,respectively. Prey preference experiments were calculated using the Manley's formula. Manley index of thripslarvae (prey I) and whitefly eggs (prey II) were 0.92 and 0.08, respectively, and for thrips larvae (prey I) andwhitefly nymphs (prey II) were 0.85 and 0.15 which shows that this predator significantly prefers thrips larvae tothe other two preys. In general, the results showed that O. niger can be used as a favorable biological controlagent for thrips in cotton fields.