Department of Zoology and Entomology, Centre for Biological Control, Rhodes University, Makhanda, PO Box 94, 6140, South Africa.
Department of Botany, Centre for Biological Control, Rhodes University, Makhanda, PO Box 94, 6140, South Africa.
Bull Entomol Res. 2021 Feb;111(1):120-128. doi: 10.1017/S0007485320000516. Epub 2020 Aug 27.
Cold winter temperatures significantly affect the biological control effort against water hyacinth, Pontederia ( = Eichhornia) crassipes Mart. (Pontederiaceae), in more temperate regions around the world. The population dynamics of the planthopper Megamelus scutellaris Berg. (Hemiptera: Delphacidae), a newly released biological control agent of water hyacinth, were recorded on the Kubusi River in the Eastern Cape Province (South Africa) over 15 months to determine the population recovery post-winter. Megamelus scutellaris incurred a severe population decline at the onset of winter when the water hyacinth plants became frost damaged. The combined effect of a population bottleneck and low minimum winter temperatures (6.12°C) below the agent's lower developmental threshold (11.46°C) caused a post-winter lag in agent density increase. Subsequently, the maximum agent population density was only reached at the end of the following summer growing season which allowed the water hyacinth population to recover in the absence of any significant biological control immediately post-winter. Supplementary releases of agents from mass-reared cultures at the beginning of the growing season (spring) is suggested as a potential method of reducing the lag-period in field populations in colder areas where natural population recovery of agents is slower.
寒冷的冬季温度会显著影响水生植物水葫芦在世界上更温和地区的生物防治效果。为了确定冬季后种群的恢复情况，在过去的 15 个月里，我们记录了在南非东开普省库布西河流域新释放的水葫芦生物防治剂南美按蚊 Megamelus scutellaris Berg. 的种群动态。当水葫芦植物遭受霜害时，南美按蚊在冬季开始时种群数量严重下降。种群瓶颈和冬季最低温度（6.12°C）低于药剂下限发育阈值（11.46°C）的综合作用导致冬季后药剂密度增加出现滞后。随后，只有在接下来的夏季生长季节结束时，才达到了最大的药剂种群密度，这使得水葫芦种群在冬季后没有任何显著的生物防治措施的情况下得以恢复。在生长季节（春季）开始时从大规模饲养的培养物中补充释放药剂被建议作为一种潜在的方法，以减少在自然种群恢复较慢的寒冷地区田间种群的滞后期。
