Moreau Gaétan, Bauce Eric
Centre de Recherche en Biologie Forestière, Département des Sciences du Bois et de la Forêt, Faculté de Foresterie et de Géomatique, Université Laval, Sainte-Foy, Québec, Canada G1K 7P4.
J Econ Entomol. 2003 Apr;96(2):280-6. doi: 10.1093/jee/96.2.280.
We conducted laboratory experiments to examine the effects of single versus double exposures of spruce budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae) female larvae to various concentrations of a Bacillus thuringiensis variety kurstaki (Btk) commercial formulation (Foray 48B). Our main objective was to document the vulnerability to Btk and the sublethal responses of fifth-instar larvae that survived from a first ingestion of Btk during their fourth stadium and to compare them with insects treated either during their fifth or fourth stadium only. As reported in the literature, fifth-instar larvae were more vulnerable than fourth-instar larvae, but only at low and medium concentrations. Fifth-instar larvae that had survived Btk ingestion during their fourth stadium were more vulnerable to a high concentration of Btk and had a shorter feeding inhibition period than those that had not been exposed during their fourth stadium. Compared with a single treatment at the fourth stadium, a double exposure to Btk further reduced the population by 20-30%, depending on the concentration applied. The second treatment also induced another feeding inhibition period and increased larval development time by 14%. The impact of the different treatments on pupal weight depended on whether treated insects exhibited supernumerary instars. In the absence of developmental polymorphism, a higher concentration, a late, or a double exposure to Btk significantly reduced pupal weight.
我们进行了实验室实验，以研究云杉芽虫（Choristoneura fumiferana，鳞翅目：卷蛾科）雌性幼虫单次暴露与两次暴露于不同浓度的苏云金芽孢杆菌库尔斯塔克变种（Btk）商业制剂（Foray 48B）的影响。我们的主要目标是记录在第四龄期首次摄入Btk后存活下来的五龄幼虫对Btk的易感性和亚致死反应，并将它们与仅在第五龄期或第四龄期接受处理的昆虫进行比较。如文献报道，五龄幼虫比四龄幼虫更易受影响，但仅在低浓度和中等浓度下如此。在第四龄期摄入Btk后存活下来的五龄幼虫比在第四龄期未接触过Btk的幼虫更容易受到高浓度Btk的影响，并且取食抑制期更短。与在第四龄期进行单次处理相比，两次暴露于Btk会使种群数量进一步减少20% - 30%，具体取决于所施用的浓度。第二次处理还诱导了另一个取食抑制期，并使幼虫发育时间增加了14%。不同处理对蛹重的影响取决于处理过的昆虫是否表现出多化性。在没有发育多态性的情况下，较高浓度、较晚或两次暴露于Btk会显著降低蛹重。
