Effects Of Fenoxycarb And Pyriproxyfen, Juvenile Hormone Analogs, On Harmonia Axyridis And Chrysoperla Sinica

In laboratory, the effects of two juvenile hormone analogues (JHAs), fenoxycarb and pyriproxyfen, on two species of natural enemies, Harmonia axyridis and Chrysoperla sinica, were determined to confirm the damage of the two JHAs to the two kinds of natural enemies and to discuss their action mechanism. These researches can help evaluate the risks of fenoxycarb and pyriproxyfen and provide theoretical basis for rational use of the two JHAs.Toxicity of fenoxycarb and pyriproxyfen to eggs, larvae, pupae and adults of Harmonia axyridis was determined by using the methods of dipping, topical contact and residual film, respectively. Significant effects of the two juvenile hormone analogs on Harmonia axyridis were found and the degree of effects depends on the stages treated and the concentrations used. Fenoxycarb and pyriproxyfen showed significant ovicidal effect on Harmonia axyridis newly-laid eggs (the LC50 were 0.0052μg/ml and 0.7406μg/ml). But have no influence on Harmonia axyridis two-day old eggs, 80% of larvae can hatch normally. Fenoxycarb and pyriproxyfen can not cause 2nd instar larvae dead directly. When the 2nd instar larvae were treated,high survival rates at the concentration 4000μg a.i./ml and 12000μg a.i./ml ( More than 90% of second instars can survive) remained. When pupae were treated, fenoxycarb and pyriproxyfen had significant effects on pupal development with adult eclosion blocked, pupa-adult intermediate and abnormalities of emerging adults. Fenoxycarb and pyriproxyfen were used evaluated their effect on survival and reproduction of Harmonia axyridis adults using direct contact and ingestion. Pyriproxyfen proved to be less harm to adult survival, whereas fenoxycarb reduced the number of adults by 65.00% and 66.67% in topical and ingestion treatment at the maximum concentration recommended (0.05μg a.i./ml and 10μg a.i./ml). The influence of fenoxycarb and pyriproxyfen on Harmonia axyridis adult fecundity. fenoxycarb and pyriproxyfen exerted a negative effect on hatching when the eggs were deposited by females treated by ingestion in the oviposition period. The hatchability were 3.23% and 36.67% (control tests were 92.7% and 95.19%) at the highest concentration tested (5μg a.i./ml and 4μg a.i./ml). The surviving adults feeded by normal Myzus persicae. Adult breed ability immediately recover (hatchability of larvae>80%).Toxicity of fenoxycarb and pyriproxyfen , two JHAs, to eggs and adults of Chrysoperla sinica was determined by using the methods of dipping, and ingestion respectively. Effects of the two juvenile hormone analogs on Chrysoperla sinica were found and the degree of effects depends on the stages treated and the concentrations used. Fenoxycarb and pyriproxyfen showed significant ovicidal effect on Chrysoperla sinica newly-laid eggs (the LC50 were 1.4958μg a.i./ml and 90.3140μg a.i./ml, respectively). But they have no obvious influence on Harmonia axyridis two-day old eggs, 85% of larvae can hatch normally at the highest concentration tested (10000μg a.i./ml and 9000μg a.i./ml). Fenoxycarb and pyriproxyfen were evaluated for their effect on reproduction of Chrysoperla sinica adults using the method of ingestion. Fenoxycarb and pyriproxyfen proved to be harmless to adult survival, 72h after treatment the number of adults by 95% at the maximum concentration recommended (100μg a.i./ml and 750μg a.i./ml). The influence of fenoxycarb and pyriproxyfen on Chrysoperla sinica adult fecundity. fenoxycarb and pyriproxyfen exerted a negative effect on hatching when the eggs were deposited by females treated by ingestion in the oviposition period. The hatchability were 83.98% and 75.00% at the lowest concentration tested (0.01μg a.i./ml and 75μg a.i./ml) after 24h. Significant difference compared with control test (95.38% and 94.87%). After 72h, the surviving adults were feeded on honey water of. Adult breed ability immediately recover (hatchability of larvae>80%).Our researches showed that Harmonia axyridis were more sensitive to the two juvenile hormone analog than Chrysoperla sinica. The two natural enemies were sensitive to fenoxycarb, compared with pyriproxyfen.