Contact effects of sulfoxaflor, spirotetramat and flonicamid on key natural enemies in citrus orchards

Türkiye is one of the most important citrus producers, where red scale, Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae), and citrus mealybug, Planococcus citri Risso (Hemiptera: Pseudococcidae), cause significant quality and yield losses. This study evaluated the contact effects of sulfoxaflor 240 g/L (15 and 20 ml/da), spirotetramat 100 g/L (75 and 100 ml/da) and flonicamid 500 g/kg (15 g/da) on the larvae, pupae, adults and eggs of the predator Chilocorus bipustulatus (L.) (Coleoptera: Coccinellidae), and on the adults of the parasitoids Leptomastix dactylopii Howard and Anagyrus pseudococci Girault (Hymenoptera: Encyrtidae), key natural enemies of P. citri, and Aphytis melinus DeBach (Hymenoptera: Aphelinidae), a key parasitoid of A. aurantii. Laboratory bioassays followed the IOBC dry-film method in a randomized complete block design with six treatments (including an untreated control) and four independent replications at 25 ± 1 °C, 65 ± 5% relative humidity and a 16/8 h light/dark photoperiod, and were complemented by semi-field cage experiments on potted orange seedlings in an uncultivated greenhouse. Corrected mortality was classified according to the rating scale of the International Organisation for Biological Control (IOBC), the laboratory scale being applied to the laboratory bioassays and the separate semi-field scale to the cage experiments. All products tested were harmless (class 1) or only slightly harmful (class 2) to the different biological stages of C. bipustulatus, with mean corrected mortality never exceeding 71%. In contrast, both doses of sulfoxaflor caused 100% mortality of all three parasitoid species under laboratory conditions and were rated harmful (class 4), whereas the lower dose of spirotetramat was harmless (class 1) to A. pseudococci adults and flonicamid was harmless (class 1) to L. dactylopii adults. Flonicamid was moderately harmful (class 3) to A. pseudococci adults in the laboratory and harmful (class 4) under semi-field conditions. Selectivity was therefore species-, dose- and exposure-dependent: sulfoxaflor was of low toxicity to C. bipustulatus but harmful to all three parasitoids in the laboratory; spirotetramat, particularly at the lower dose, was harmless or slightly harmful to A. pseudococci but slightly to moderately harmful to L. dactylopii; and flonicamid differed sharply between the two parasitoids of P. citri. Recommendations for the use of these insecticides in integrated pest management should therefore take account of the natural enemy species present.