Bollworms and sap-sucking insect pests are a significant constraint to cotton production in Africa. Manual topping of cotton plants, which consists of cutting off the top of the plant, i.e. the terminal bud of the main stem, is a promising alternative to chemical control by removing resources for certain pests or inducing plant defences. In this study, we evaluated the level of protection by topping against bollworms and sap-sucking insect pests and the effect of topping on seed cotton yield. Six experiments combining insecticide protection (sprayed vs. unsprayed plots) and topping (topped vs. non-topped plots) were conducted in Mali and Senegal. Topping by itself conferred weak protection against bollworms with an 11% reduction in the proportion of damaged shed squares and bolls, compared to insecticide protection (−55%). Topping had a low to moderate effectiveness in reducing the incidence of sap-sucking pests (−20 to −48%), but equivalent to insecticide treatments. Although topping significantly reduced the proportion of damaged bolls (−31%) at harvest in the absence of insecticide protection, this did not substantially affect seed cotton yield (+4%), unlike insecticide protection (+52%). However, this technique could be advantageously combined with threshold-based interventions integrating biopesticides to reduce the environmental impact of crop protection in cotton.

中文翻译：

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人工打顶对虫害发生率和棉花产量的影响


棉铃虫和吸汁害虫是非洲棉花生产的重要制约因素。棉花植株的人工打顶，包括切断植株的顶部，即主茎的顶芽，是通过去除某些害虫的资源或诱导植物防御来替代化学防治的一种很有前途的替代方案。在这项研究中，我们评估了打顶对棉铃虫和吸汁害虫的保护水平，以及打顶对籽棉产量的影响。在马里和塞内加尔进行了 6 个实验，将杀虫剂保护（喷洒与未喷洒的地块）和打顶（打顶与未打顶的地块）相结合。与杀虫剂保护 （-55%） 相比，打顶本身对棉铃虫的保护较弱，受损的棚块和棉铃的比例减少了 11%。打顶在降低吸汁害虫的发生率（-20 至 -48%）方面具有低到中等效果，但与杀虫剂处理相当。尽管在没有杀虫剂保护的情况下，打顶显著降低了收获时受损棉铃的比例 （-31%），但与杀虫剂保护不同 （+52%），这并没有显着影响籽棉产量 （+4%）。然而，这项技术可以有利地与基于阈值的干预措施相结合，整合生物农药，以减少棉花作物保护对环境的影响。