ABSTRACT

Alternatives to pesticides to control the rosy apple aphid, Dysaphis plantaginea, are being developed. Natural enemies usually arrive too late after the first aphid infestation to provide effective control. This study tested the effects of mass release of two parasitoid species, Aphidius matricariae and Ephedrus cerasicola, on the numbers of aphid colonies and aphids per tree. In a trial undertaken in two years in an organic apple orchard, parasitoids were released three times early in the season to match the presence of aphid fundatrix (sensitive stages), on a weekly or bi-weekly frequency. The degree-days necessary for parasitoid emergence in the field after release were calculated. A sufficient level of aphid control by parasitoids was reached during the first month of the survey (March), but for both release treatments the control mostly failed during the second part of the monitoring session (April to late May) compared with the control treatment with neem oil. The relative effects of release frequencies were different between the two years, probably because of interannual differences in aphid population dynamics and initial infestation in orchards. The field survey suggested that parasitoid releases, at either frequency, were promising candidates for biological control of the rosy aphid, although the method still needs further calibration. This case study laid the first empirical basis to help develop future control methods of aphids by parasitoid releases in apple orchards. Releases should be done one to two weeks before first aphid detection to account for long development times of parasitoids at relatively low temperatures.

摘要

正在开发用于控制玫瑰色苹果蚜虫Dysaphis plantaginea的杀虫剂替代品。天敌通常在第一次蚜虫侵扰后到达太晚，无法提供有效控制。本研究测试了两种寄生蜂Aphidius matricariae和Ephedrus cerasicola大规模释放的影响，关于每棵树的蚜虫群落和蚜虫数量。在两年内在有机苹果园进行的一项试验中，寄生蜂在季节早期释放了 3 次，以匹配蚜虫根部（敏感阶段）的存在，每周或每两周一次。计算释放后田间寄生蜂出现所需的度数天数。在调查的第一个月（3 月）期间，寄生蜂对蚜虫的控制达到了足够的水平，但对于两种释放处理，与控制处理相比，在监测期的第二部分（4 月至 5 月下旬），控制大多失败。印楝油。两年间释放频率的相对影响不同，这可能是由于蚜虫种群动态和果园初始侵染的年际差异。实地调查表明，以任何一种频率释放寄生蜂都是有希望的生物防治玫瑰蚜虫的候选者，尽管该方法仍需要进一步校准。该案例研究奠定了第一个经验基础，以帮助开发未来通过在苹果园释放寄生蜂来控制蚜虫的方法。应在首次检测蚜虫前一到两周进行释放，以说明寄生蜂在相对较低的温度下的较长发育时间。