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The genus Diatraea (Lepidoptera: Crambidae) includes stem borers representing the most critical sugarcane pests in the Americas. Colombia’s most widely distributed and damaging Diatraea species include Diatraea saccharalis, D. indigenella, D. busckella, and D. tabernella. The reduced efficacy of biological tools commonly used in controlling several species highlights the importance of evaluating alternative management strategies, such as transgenic plants expressing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt). The selection of optimal Bt insecticidal proteins for Diatraea control depends on bioassays with purified Bt proteins. Because there is no described artificial diet for borer species other than D. saccharalis and availability of most purified Bt toxins is restricted, this study aimed at developing a bioassay method using fresh corn tissue and providing proof of concept by testing susceptibility to the Cry1Ac insecticidal protein from Bt. Toxicity was evaluated with a single Cry1Ac dose applied directly to corn discs. Stem borer mortality after seven days was higher than 90% for all four tested Diatraea species, while control mortality was below 8%. In addition, we observed that Cry1Ac caused more than 90% weight inhibition in all survivors and delayed development. These results validate the use of this method to determine mortality and growth inhibition due to the consumption of the Cry1Ac protein in each of the Diatraea species. Furthermore, this method could be used to assess other entomopathogenic substances to control these insect pests.

钻茎螟属（Diatraea）隶属于鳞翅目草螟科，该属涵盖钻茎螟类害虫，为美洲地区最具危害性的甘蔗钻蛀性害虫。哥伦比亚分布最广、危害最为严重的钻茎螟属物种包括甘蔗二点螟（Diatraea saccharalis）、本土钻茎螟（D. indigenella）、巴斯克钻茎螟（D. busckella）以及塔伯纳钻茎螟（D. tabernella）。当前用于防治该属多种物种的生物防治工具效力衰减，凸显了评估替代防治策略的必要性，例如表达苏云金杆菌（Bacillus thuringiensis, Bt）杀虫蛋白的转基因作物。筛选用于防治钻茎螟属物种的最优Bt杀虫蛋白，需依托使用纯化Bt蛋白的生物测定实验。由于除甘蔗二点螟外，其余钻茎螟物种尚未建立标准化人工饲养饲料，且多数纯化Bt毒素的获取途径受限，本研究旨在开发一种利用新鲜玉米组织的生物测定方法，并通过测试对Bt来源的Cry1Ac杀虫蛋白的敏感性开展概念验证。研究通过将单一剂量的Cry1Ac直接施加于玉米圆盘上，评估其毒性。经七天培养后，四种供试钻茎螟物种的幼虫死亡率均高于90%，而对照组死亡率低于8%。此外，本研究发现Cry1Ac可使所有存活幼虫的体重抑制率超过90%，并延缓其生长发育。上述结果证实，该方法可用于测定四种供试钻茎螟物种取食Cry1Ac蛋白后的死亡率与生长抑制情况。此外，该方法还可用于评估其他用于防治此类害虫的昆虫病原物质。