Juvenoids On Aphids To Prolong Optimal Stages

In recent years, Aphidius gifuensis, a critical parasitoid, has been increasingly used to control Myzus persicae in tobacco. However, problems due to inconsistent emergence and insufficient numbers of A. gifuensis to control M. persicae have arisen in artificial reproduction. Here, we investigated the effects of the juvenoids ZR-512, ZR-777, ZR-515, fenoxycarb and juvenile hormone (JH) III on the performance of M. persicae, the activities of molting enzymes and parasitism rates. The aim was to identify juvenoids that may prolong the 'arrived too early' optimal stages of M. persicae for A. gifuensis parasitism to address the problems mentioned above. The results showed that the developmental durations of 2nd- and 3rd-instar nymphs of the parental (F-0) and offspring (F-1) generations of M. persicae were significantly prolonged by juvenoid treatment. The instar durations ranged from 4.00 to 13.67 h for the parental generation and from 8.00 to 32.00 h for the offspring. M. persicae lifespan was not significantly affected by the juvenoids, whereas fecundity was. Additionally, the phenoloxidase and chitinase contents and activities in M. persicae were significantly reduced by the juvenoids, whereas the parasitism rate of A. gifuensis on M. persicae was unaffected. Our study provides information that can help prolong the 'arrived too early' period of effective parasitism of M. persicae nymphs by A. gifuensis and thereby benefit the large-scale artificial reproduction of A. gifuensis. These findings will enhance the biological control of M. persicae and highlight the mechanism by which juvenoids affect M. persicae development by regulating phenoloxidase or chitinase.