College of Agriculture, Shanxi Agricultural University, Taigu, Shanxi, China.
College of Life Science, Shanxi Agricultural University, Taigu, Shanxi, China.
Insect Sci. 2020 Feb;27(1):159-169. doi: 10.1111/1744-7917.12611. Epub 2018 Aug 9.
Agasicles hygrophila has been introduced worldwide as a control agent for the invasive weed Alternanthera philoxeroides. However, global warming has potential impact on its controlling efficacy. The aim of this research was to explore the primary factors responsible for the greatly reduced A. hygrophila population in hot summers. To imitate the temperature conditions in summers, different developmental stages of A. hygrophila were treated with high temperatures from 32.5 °C to 45 °C for 1-5 h. Based on the survival rate, the heat tolerance of each developmental stage was ranked from lowest to highest as follows: egg, 1st, 2nd, 3rd instar larva, adult and pupa. Eggs showed the lowest heat tolerance with 37.5 °C as the critical temperature affecting larval hatching. Heat treatment of the A. hygrophila eggs at 37.5 °C for 1 h decreased the hatch rate to 24%. Our results indicated that when compared with the control at 25 °C, 1 h treatment at 37.5 °C prolonged the duration of the egg stage, shortened the duration of oviposition and total longevity, and changed the reproductive pattern of A. hygrophila. The net reproductive rate, intrinsic rate and finite rate were all significantly reduced. The results suggest that low heat tolerance of the eggs was the major factor responsible for the reduction of A. hygrophila populations, and the key temperature was 37.5 °C. Therefore, appropriate measures should be taken to protect eggs in order to maintain the efficacy of A. hygrophila in the biological control of A. philoxeroides in hot summers.
水棘针已在全球范围内被引入作为入侵杂草空心莲子草的防治剂。然而，全球变暖可能会对其防治效果产生影响。本研究旨在探索导致夏季高温下水棘针种群大量减少的主要因素。为了模拟夏季的温度条件，将不同发育阶段的水棘针在 32.5°C 至 45°C 的高温下处理 1-5 小时。根据存活率，将各发育阶段的耐热性从低到高排序如下：卵、1 龄、2 龄、3 龄幼虫、成虫和蛹。卵的耐热性最低，37.5°C 是影响幼虫孵化的临界温度。将水棘针卵在 37.5°C 下处理 1 小时，孵化率降至 24%。结果表明，与 25°C 下的对照相比，37.5°C 处理 1 小时延长了卵期持续时间，缩短了产卵期和总寿命，并改变了水棘针的繁殖模式。净生殖率、内禀增长率和有限增长率均显著降低。结果表明，卵的耐热性低是水棘针种群减少的主要原因，关键温度为 37.5°C。因此，应采取适当措施保护卵，以维持水棘针在夏季高温下防治空心莲子草的效果。
