Locust swarm control is still a main topic in agriculture and is often based on the extensive use of chemical agents that can be problematic for the environment and human health. Currently, only a few alternative control agents are available on the market, such as neem oil, the fungus Metarhizium sp., and the microsporidian Paranosema locustae. In this study, we improved the formulation of a botanical insecticide that is based on linseed oil and was found to be effective against the desert locust, Schistocerca gregaria. To make sure that linseed oil is most effective, we first tested several natural plant oils in a comparative laboratory study. Linseed oil performed best and resulted in 100% mortality within only 2 days after a single spray treatment. However, this linseed oil formulation contains three expensive essential oils, thus we further improved it to avoid costly essential oils. A much lower concentration of linseed oil was also found to be highly effective and killed adult S. gregaria within 3 days in an experiment performed under semifield conditions. Furthermore, a concentrated stock solution of this botanical insecticide was developed to increase stability and reduce shipping costs in areas where water for dilution is available. Mechanical treatment, applied during the preparation of this linseed oil emulsion, resulted in the formation of micro-colloids, which prevent the separation of phases and enable 1:16 dilution with water containing bicarbonate. Interestingly, only 24 h after single spray treatment, locusts became immobile and most of them were unable to jump, which would make them easy prey for natural enemies. Later, insects died due to the hardening of the linseed oil emulsion. This novel linseed oil emulsion is harmless for humans, rather easy to produce, and remains stable over weeks in its concentrated form, which suggests that it is promising alternative agent for locust control.

中文翻译：

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使用可稀释亚麻籽油乳液替代蝗虫控制

蝗群控制仍然是农业的一个主要话题，并且通常基于化学制剂的广泛使用，这可能会给环境和人类健康带来问题。目前，市场上只有少数替代控制剂，例如印楝油、真菌绿僵菌和微孢子虫Paranosema locustae。在这项研究中，我们改进了一种以亚麻籽油为基础的植物杀虫剂配方，结果发现该杀虫剂对沙漠蝗虫（Schistocerca gregaria）有效。为了确保亚麻籽油最有效，我们首先在比较实验室研究中测试了几种天然植物油。亚麻籽油表现最佳，单次喷雾处理后仅 2 天内死亡率就达到 100%。然而，这种亚麻籽油配方含有三种昂贵的精油，因此我们对其进行了进一步改进，以避免使用昂贵的精油。在半田间条件下进行的实验中，浓度低得多的亚麻籽油也被发现非常有效，可在 3 天内杀死成体亚麻籽油。此外，还开发了这种植物杀虫剂的浓缩原液，以提高稳定性并降低在有稀释水的地区的运输成本。在制备这种亚麻籽油乳液过程中采用的机械处理导致微胶体的形成，从而防止相分离并能够用含碳酸氢盐的水进行 1:16 稀释。有趣的是，单次喷雾处理后仅24小时，蝗虫就变得一动不动，大多数无法跳跃，这使它们很容易成为天敌的猎物。后来，昆虫因亚麻籽油乳液硬化而死亡。这种新型亚麻籽油乳液对人类无害，相当容易生产，并且其浓缩形式在数周内保持稳定，这表明它是有前途的蝗虫控制替代剂。