桃小食心虫发育过程中蜕皮激素滴度动态及甲氧虫酰肼干扰滞育的作用

【目的】 经历了长光照和短光照条件，桃小食心虫Carposina sasakii脱果老熟幼虫分别进行非滞育和滞育发育。本研究旨在通过使用蜕皮激素类似物甲氧虫酰肼对桃小食心虫滞育进行干扰，以期达到干扰桃小食心虫滞育的目的，为开发桃小食心虫防治新方法奠定基础。【方法】 利用ELISA法测定了桃小食心虫幼虫滞育和非滞育过程中的20E滴度动态；以清水为对照，测定了不同浓度(0.05, 0.1, 1,2, 5, 7.5和10 mg/mL)甲氧虫酰肼以及0.5和1 mg/mL 20E喷沙处理对桃小食心虫结茧的影响；测定了5mg/mL甲氧虫酰肼和1 mg/mL 20E喷沙处理中桃小食心虫20E滴度，并跟踪调查了0.1和5 mg/mL甲氧虫酰肼喷沙处理对桃小食心虫滞育的干扰效果。【结果】两种光周期(15L∶9D和12L∶12D)下桃小食心虫滞育和非滞育幼虫生长过程中20E滴度没有差异，均是从幼龄到老龄逐渐降低，脱果时达到最低；但脱果时，长光照非滞育发育幼虫体内20E滴度(0.473 ng/g)显著高于短光照注定滞育幼虫体内的(0.254 ng/g)。非滞育发育幼虫脱果后进入长茧化蛹，虫体20E的滴度显著升高，在蛹期保持较高滴度区间(0.652~1.217ng/g)。滞育发育幼虫脱果后进入圆茧滞育，20E滴度缓慢上升，第4天达到第一个峰值(0.656 ng/g)，随后降低，在第8天达到第2个峰值(0.790 ng/g)；随着进入滞育稳定期，20E滴度逐渐降低；70 d后达到滞育解除状态，20E滴度持续保持在低滴度水平；第90天达到滞育期间最低滴度(0.424 ng/g)，随后20E滴度开始上升。0.05 mg/mL甲氧虫酰肼点滴短光照桃小食心虫脱果幼虫，即可干扰部分滞育圆茧的形成，对桃小食心虫脱果幼虫的LD₅₀为7.039 μg/头。0.05 mg/mL以上浓度甲氧虫酰肼和20E喷沙处理均可有效干扰滞育圆茧的形成，1 mg/mL相同浓度的20E比甲氧虫酰肼表现出的干扰活性更高，两者均能使注定滞育的幼虫出现结长茧、畸形茧以及无法结茧的表型；在结畸形茧和无法结茧幼虫中20E滴度显著升高，5 mg/mL甲氧虫酰肼和1 mg/mL 20E喷沙处理不能结圆茧的比例分别为70.0%和66.7%，其中结畸形茧的幼虫体内20E滴度分别显著升高16.3%和143.0%，异常不能结茧的幼虫体内20E滴度分别显著升高149.3%和278.6%。部分幼虫接触甲氧虫酰肼后虽能够结圆茧，但能够完成滞育成功羽化的比例减少，甲氧虫酰肼0.1 mg/mL喷沙处理组羽化率仅为20.8%。【结论】 桃小食心虫幼虫在滞育过程中20E保持较低滴度，在生殖发育阶段需要较高滴度。外源甲氧虫酰肼和20E均能够干扰其结圆茧滞育，虫体结茧表型与20E滴度增加幅度具有相关性，相同浓度的20E比甲氧虫酰肼表现出更高的干扰活性；甲氧虫酰肼处理减少了桃小食心虫幼虫成功完成滞育的比例。

Dynamics of ecdysone titer and the interference of methoxyfenozide on diapause during thedevelopment ofCarposina sasakii(Lepidoptera: Carposinidae)

【Aim】 Under short and long light photoperiod, the mature larvae of Carposinasasakii undergo diapause and non-diapause development, respectively. This study aims tointerfere with the diapause of C. sasakii by using the ecdysone analog methoxyfenozide soas to lay a foundation for the new control technologies for C. sasakii. 【Methods】 The 20Etiter dynamics in C. sasakii during larvae diapause and non-diapause developments weremeasured by ELISA. The interference effect of methoxyfenozide (0.05, 0.1, 1, 2, 5, 7.5and 10 mg/mL) and 20E (0.5 and 1 mg/mL) on the cocoon formation of C. sasakii wasdetermined using the sandblast method with pure water as the control. The effects of 5mg/mL methoxenozide and 1 mg/mL 20E sandblasting treatments on the 20E titer of C. sasakiiwere measured, and the effect of sandblasting with 0.1 and 5 mg/mL methoxenozide on thediapause of C. sasakii were investigated subsequently. 【Results】 There was no differencein 20E titer in the developmental process between diapause and non-diapause larvae of C.sasakii under two photoperiods (15L∶9D and 12L∶12D), and both gradually decreased withthe increase of instar and reched the lowest when they escaped off fruits. However, the 20Etiter in non-diapause larvae escaping off fruits under long photoperiod (0.473 ng/g) wassignificantly higher than that in diapause larvae escaping off fruits under shortphotoperiod (0.254 ng/g). The non-diapause developmental larvae entered the long cocoonpupation after defruiting, and the 20E titer increased significantly and maintained a highlevel (0.652-1.217 ng/g) in the pupal stage. The diapause developmental larvae entered the round cocoon diapause after defruiting, and the 20E titer slowly increased in the firstfour days, reaching the first peak (0.656 ng/g) on the 4th day, then decreased and thenincreased again, reaching the 2nd peak (0.790 ng/g) on the 8th day. With the entry ofdiapause stabilization period, the 20E titer gradually decreased. After 70 d, the diapausewas relieved, and the 20E titer remained at a low level. The lowest titer (0.424 ng/g) ofdiapause period was reached on the 90th day, and then the 20E titer began to rise.Methoxyfenozide at the concentration of 0.05 mg/mL could interfere with the formation ofdiapause round cocoons of C. sasakii larvae escaping off fruits under short photoperiod,and the LD₅₀ value of methoxyfenozide to mature defruiting larvae of C. sasakii was 7.039μg/individual. Both methoxyhydrazine and 20E at the concentration of more than 0.05 mg/mLsprayed on the sand surface could effectively interfere with the formation of diapauseround cocoons of C. sasakii, and 20E showed higher interference activity thanmethoxyfenozide at the same concentration of 1 mg/mL. Both of them could make the diapauselarvae produce long cocoon, abnormal cocoon and non-cocooning reaction, and the 20E titerin abnormal cocoon and non-cocooning larvae increased significantly. The percentages ofcocooning failure in 5 mg/mL methoxyfenozide and 1 mg/mL 20E sand spraying treatments were70.0% and 66.7%, respectively. The 20E titers in abnormal cocooning larvae significantlyincreased by 16.3% and 143.0%, respectively. The 20E titers in non-cocooning larvaesignificantly increased by 149.3% and 278.6%, respectively. Although some larvae couldform round cocoons after being exposed to 0.1 mg/mL methoxyfenozide, the proportion oflarvae successfully completing diapause and eclosion reduced, and the eclosion rate wasonly 20.8%. 【Conclusion】 The 20E titer in C. sasakii keeps a low titer during thediapause process, and a higher titer is needed in the reproductive developmental stage.Moreover, methoxyfenozide and 20E can interfere with its diapause state forming roundcocoons. The increase range of 20E titer is consistent with the change of cocooningphenotype, and 20E shows higher interference activity than methoxyfenozide at the sameconcentration. Methoxyfenozide reduces the proportion of larvae successfully completingdiapause.