Functional response of Iphiseius degenerans (Acari: Phytoseiidae) to Eutetranychus orientalis (Acari: Tetranychidae),a new pest of Citrus in Eastern-Mediterranean, Turkey

Abstract: In recent years, Eutetranychus orientalis (Klein) (Acari: Tetranychidae) has becomeone of the most common pests of Citrus in the Eastern-Mediterranean part of Turkey, a regionproducing 80% of total Citrus fruits in the country. The use of chemical control is the commonpractice in the Citrus orchards in this region. Therefore, it is possible in the near future the pestto develop resistance to acaricides, if Citrus growers maintain their habits of the frequentacaricide applications. In this regard, sustainable mite control programs including the use ofphytoseiid mites is one of the most promising methods for the management of E. orientalis.Among the phytoseiid mites, Iphiseius degenerans (Berlese) (Acari: Phytoseiidae) is anabundant predatory mite in Citrus orchards in all Mediterranean countries and it is expected tohave high predation efficiency against E. orientalis. In this study, we determined functionalresponse of I. degenerans on eggs and larvae of E. orientalis under lab conditions (25 ± 1 °Cand 16:8 L:D). In the experiments, six different prey densities (5, 10, 20, 40, 60 and 80) of eachdevelopmental stage were separately offered to the predatory mite for 24 hours. According tologistic regression analysis, I. degenerans showed a Type II functional response on both stagesof the prey. However, the predation rates on larvae were significantly higher than those on eggsat all prey densities (t-test, P < 0.001). The attack rates and the handling time (Th) of the TypeII response were calculated by fitting data to Holling’s disc equation. While the α coefficientswere found to be 0.957 and 1.146, the Th coefficients were determined to be 0.111 and 0.014for eggs and larvae, respectively. Our results indicated that I. degenerans could be a promisingcandidate for the biological control of E. orientalis in Turkey.