Effects of a juvenile hormone analog, pyriproxyfen, on Serangium japonicum (Coleoptera: Coccinellidae), a predator of Bemisia tabaci (Hemiptera: Aleyrodidae)

• The lethal effects of pyriproxyfen on the ladybeetle Serangium japonicum were evaluated.
• Pyriproxyfen caused high mortality to eggs but not larval or pupal stages of S. japonicum.
• Pyriproxyfen delayed larval development of S. japonicum.
• S. japonicum adults that fed on pyriproxyfen-treated whitefly eggs laid fewer eggs than untreated adults.

Pyriproxyfen is a juvenile hormone analog that has been widely used to control whiteflies and various other insect pests. Serangium japonicum is a dominant coccinellid predator of Bemisia tabaci (biotype B or MEAM1) in many agricultural systems in China. We assessed the toxicity of pyriproxyfen to S. japonicum to explore the compatibility of using pyriproxyfen and S. japonicum together to control B. tabaci. Eggs and pupae of S. japonicum were dipped into the pyriproxyfen solutions [100 mg (AI)/L and 200 mg (AI)/L] or solvent and water controls. Larvae were fed pyriproxyfen-treated B. tabaci eggs and the adults were fed pyriproxyfen-treated fourth instar nymphs. Significant effects of pyriproxyfen on all immature stages of S. japonicum were found, and the degree of effects depends on the stage treated and the concentration tested. Pyriproxyfen caused significant mortality of S. japonicum eggs, with only 3.3% survival rates at the higher concentration and 17.3% at the lower concentration. Development time of S. japonicum of treated larval instars to adult emergence was longer than that of the untreated larvae. The fourth instar was the most susceptible larval stage, while the egg was the most sensitive stage of S. japonicum. Moreover, pyriproxyfen significantly decreased oviposition by S. japonicum adults and subsequent offspring hatching rate. In conclusion, the S. japonicum egg was the most sensitive stage to pyriproxyfen. Thus for a combined pyriproxyfen–S. japonicum whitefly control program, applying pyriproxyfen after S. japonicum egg hatch would minimize the effects of pyriproxyfen on the S. japonicum population.

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