Evaluation of natural active ingredients for the protection of potato tubers from wireworm damage

The EU has established ambitious goals for reducing pesticide use. Therefore, research should focus on effective IPM, including for wireworms, as they are a threat to potatoes and other arable crops. When wireworm populations exceed the damage threshold, it is important to have effective non-chemical alternatives available. However, few effective alternatives, such as natural products, are currently available for wireworm control. The present work assesses the potential of natural products for the protection of daughter potatoes from wireworm damage. Trials were carried out over 3 years in semi-natural conditions, with pots used to introduce a set number of reared wireworms, and in field conditions via drip irrigation. The wireworm species studied was Agriotes sordidus. Trials in semi-natural conditions showed that the only products with great potential for causing wireworm mortality and protecting potatoes were the two based on geraniol + thymol and clove oil. They were not, however, as effective in field trials, although statistically significant reductions in infestation level and/or pest incidence were observed. These reductions were similar to those produced in field trials with azadiractin, Beauveria bassiana strain ATCC 74040, and chestnut tannin extract. In pot trials, these three natural products, however, proved ineffective, or much less effective than the previous two. Our research suggests that the effectiveness of these products can be improved if the desired active ingredient is evenly applied in higher concentrations around the daughter potatoes.