AbstractA larval population of spruce budworm, Choristoneura fumiferana (Clemens), was monitored for 5 d following aerial application of a commercial formulation of Bacillus thuringiensis Berliner subsp. kurstaki to investigate dose acquisition and expression (larval mortality, recovery, feeding, and growth) in relation to spray deposition and persistence of spray deposits. The main objective was to test if previous laboratory observations on how B. thuringiensis affects feeding and dose ingestion by spruce budworm larvae hold true under field conditions. About 40% of the treated population ingested a lethal dose within 1 d after spray application. Lethally dosed larvae died without further feeding upon transfer from treated foliage to (untreated) artificial diet. Resumption of feeding by larvae that survived the treatment was delayed relative to larvae from the control population during 3 d following spray application; during that time, normal feeding activity and larval weight gain were suppressed. Inhibited feeding by survivors appeared to prevent further dose uptake because the proportion of lethally dosed larvae in daily collections did not increase despite significant residual spray deposits in budworm feeding sites. Restoration of "normal" recovery times by the fourth day coincided with a 65–85% reduction in persistence of the pathogen on the foliage and did not result in further lethal dose acquisition, as treatment-induced mortality dropped to about 20% on the 4th and 5th days. The observations are consistent with previous laboratory observations of how B. thuringiensis affects larval feeding and with the hypothesis that feeding inhibition may be a limiting factor in the acquisition of a lethal dose.
摘要 在空中施用苏云
金芽孢杆菌柏林亚种(Bacillus thuringiensis Berliner subsp. kurstaki)商业制剂后,对云杉芽虫(Choristoneura fumiferana (Clemens))的幼虫种群进行了 5 天的监测,以研究剂量的获得和表达(幼虫死亡率、恢复、摄食和生长)与喷雾沉积和喷雾沉积物持久性的关系。主要目的是检验之前在实验室观察到的苏云
金杆菌如何影响云杉芽虫幼虫摄食和摄取剂量的情况在田间条件下是否成立。喷洒后 1 d 内,约 40% 的受处理种群摄取了致死剂量。经致死剂量处理的幼虫从处理过的叶片转移到(未处理的)人工饲料后,没有继续取食就死亡了。相对于对照种群的幼虫,处理后存活的幼虫在喷洒后 3 d 内恢复摄食的时间有所延迟;在此期间,正常的摄食活动和幼虫体重增加都受到抑制。存活下来的幼虫摄食受到抑制似乎阻止了剂量的进一步吸收,因为尽管芽虫摄食点有大量残留喷雾沉积物,但每天收集的致死剂量幼虫比例并没有增加。在第四天恢复 "正常 "恢复时间的同时,病原体在叶片上的持续时间减少了 65-85%,并且没有导致进一步的致死剂量吸收,因为在第四天和第五天,处理引起的死亡率下降到 20%左右。这些观察结果与之前苏云
金杆菌如何影响幼虫摄食的实验室观察结果一致,也与摄食抑制可能是获得致死剂量的限制因素这一假设一致。