释放不同益害比多异瓢虫对设施豇豆豆蚜的防效及定殖影响

设施豇豆生产中常遭受豆蚜Aphis craccivora(Koch)为害，蚜害可导致豇豆产量、品质下降等问题出现。多异瓢虫Hippodamia variegata(Goeze)为豆蚜的重要天敌，在豇豆生产用温室内，按多异瓢虫和豆蚜益害比1:10、1:20、1:40、1:60及1:80比例分别释放多异瓢虫成虫；同时，设置未释放天敌对照区。调查豆蚜和多异瓢虫种群数量和结构动态变化，比较豆蚜虫口减退率、防治效果、多异瓢虫定殖率及种群增长率等指标，确定持续防治豆蚜的最佳益害比。结果表明，在按益害比1:10和1:20释放多异瓢虫5～35 d后，其对豆蚜防效可达90%以上；但防治后期多异瓢虫定殖率低，防治成本较高。按益害比1:80释放多异瓢虫3～7 d后，对豆蚜防效高于60%，释放后期防效持效期为7 d，防治后期瓢虫定殖率和种群定殖速度较高。益害比为1:60和1:80时防治后期防效低、持效期短，但定殖率高于其他益害比。益害比1:40则兼具防效好和定殖率高的特点，可持续控制设施豇豆豆蚜的为害，是最佳释放比例。推荐将1:40作为多异瓢虫防治豇豆上豆蚜的参考益害比。

Influence of Releasing Hippodamia variegate at Different Natural Enemy/Pest Ratios on the Control and Colonization of Aphids craccivora on Cowpea in Protected Cultivation

Aphis craccivora (Koch) is an important cowpea pest, which often causes serious loss to yield and quality in cowpea. Hippodamia variegata (Goeze) is an important natural enemy of A. craccivora in cowpea production greenhouse. Adults of H. variegata were released at the natural enemy/pest ratios of 1:10, 1:20, 1:40, 1:60, and 1:80 on cowpea in the greenhouse, and cowpea unreleased with H. variegata was used as the control. To determine the best natural enemy/pest ratios for sustained control of A. craccivora by releasing H. variegata, we investigated the decline rate of the released A. craccivora, colonization rate and growth rate of H. variegate, the control efficiency of the released natural enemy against A. craccivora, and the population dynamics of A. craccivora and H. variegata. The results showed that control of A. craccivora was over 90% at 5—35 d after release of predators at the natural enemy/pest ratios of 1:10 and 1:20. However, colonization of H. variegata in the greenhouse was low and the cost was high. When the predators were released at the natural enemy/pest ratios of 1:80, the control of A. craccivora was above 60% at 3―7 d after release and the effective period was only 7 d. The colonization rate and growth rate of H. variegata increased. When the natural enemy/pest ratios were 1:60 and 1:80, the control was low in late stage and the effective duration was short, but the colonization rate of the predators was higher than that of the other natural enemy/pest ratios. The natural enemy/pest ratio of 1:40 was characterized by high control of A. craccivora and colonization of H. variegata in the greenhouses and could afford sustainable control of cowpea A. craccivora. These results indicate that the natural enemy/pest ratio of 1:40 can be used as a reference for control of A. craccivora in cowpea production in greenhouse.