Project description

The sustainable regulation of wireworm populations is becoming increasingly important. Rising average temperatures, more frequent dry periods and the increasingly limited availability of soil-active insecticides in the entire crop rotation are directly linked to increasing pest pressure from wireworms.

As part of the "Wireworm Control" project, various control measures against the wireworm are being evaluated. One promising approach to wireworm control is the optimisation of tillage intensity and tillage timing, taking into account the activity phases of click beetles. The effectiveness of this measure is being evaluated as part of a comprehensive and practical study design. To this end, one-year and multi-year trials will be carried out in various regions within the usual regional crop rotations in potato and maize cultivation. Furthermore, trials with insect-pathogenic fungi, attractant strips, press residues and insecticides will also be carried out. As part of the project, trials are also carried out in the greenhouse and in the laboratory. Here, under controlled conditions, more detailed knowledge is gained about the preferred oviposition sites of female click beetles, the carrier material of insect-pathogenic fungi is optimised and the influence of fertilisers and soil additives on the vitality and development of wireworms is investigated. In the project, wireworms are also collected and determined directly after the potato harvest and from damaged maize plants in order to systematically record the relevant pest species in the regions and develop targeted control measures.

In the final year of the project, the publication of a catalogue of recommendations to support farmers and agricultural advisors is planned based on the project results.

Interim results

• Multiple superficial tillage between cereal harvest and cultivation of the winter cover crop, or also in spring, for example as part of mechanical weed control, leads to a reduction in the wireworm population (predominant wireworm species at the trial sites: Agriotes ustulatus, A. sputator and A. brevis).
• With late cultivation (end of August, beginning of September), winter greening has no influence on the wireworm population (predominant wireworm species at the trial site: A. ustulatus).
• For preceding crops with a later sowing date (e.g. millet), lower wireworm numbers were recorded in the following year than for preceding crops with an earlier sowing date (e.g. emmer) (predominant wireworm species at the trial site: A. sputator and A. brevis).
• Previous tests with various fertilisers and soil additives, including humic substances, plant extracts and calcium cyanamide, showed no measurable effect on the vitality of wireworms compared to the untreated control. This was established in laboratory trials with single and tenfold application rates and a trial period of five weeks.
• The use of attractant plants in combination with insect-pathogenic fungi can reduce the population of wireworms in potatoes and maize. The greatest challenges currently lie in the choice of cultivation time for the attractant plants, in the cultivation technique and in hoeing and mulching the attractant plants.
• Under practical conditions, insect-pathogenic fungi(Metarhizium brunneum) achieved an average efficiency of 10 % with sufficient precipitation.
• In a multi-year field trial, the addition of water-storing hydrogel did not improve the efficacy of insect-pathogenic fungi(M. brunneum).
• The addition of chitosan to the culture medium leads to an improvement in the germination capacity and sporulation of insect-pathogenic fungi (M. brunneum).
• Clover and wheat are particularly attractive for click beetle females (A. sputator) (laboratory olfactometer result).

Benefits of the project

The resilience of wireworms and their perennial development require site-specific, multi-year strategies in which several measures must be combined in order to effectively reduce the wireworm population. As part of the "Wireworm Control" project, available control measures are being evaluated in terms of their effectiveness and sustainability. In addition, new measures against the wireworm are being developed in close cooperation with practitioners. The results of the practical trials will ultimately be incorporated into the development of recommendations for action. The catalogue of recommendations will include the measures tested in the project as well as an assessment of their effectiveness, sustainability and practicability.