Wireworms

Agriotes

Changed on: 21.05.2019
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Wireworms are common in all growing positions, but their occurrence is often impact specific. In individual years, damage of varying severity was reported, although damage was more likely to occur in hot, dry years. The adult beetles are found for a short period between March and August, with the flight phase depending on the species. As the wireworms take three to five years to develop, they can be found in the ground throughout the year.

The female beetles lay their translucent eggs in the ground a few days after their cuticle has hardened. The eggs are laid by hearth and not evenly over the field. Densely overgrown areas are preferred to bare arable land. After about 4 weeks - depending on the temperature - the larvae hatch. These initially measure only 1.5 mm in length and are whitish in colour. The larvae develop over several years and, depending on the environmental conditions, they pass through a varying number of larval stages. In the course of the larvae skinning, longer periods of rest are repeatedly passed through.

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Wireworms are common in all growing positions, but their occurrence is often impact specific. In individual years, damage of varying severity was reported, although damage was more likely to occur in hot, dry years. The adult beetles are found for a short period between March and August, with the flight phase depending on the species. As the wireworms take three to five years to develop, they can be found in the ground throughout the year.

The female beetles lay their translucent eggs in the ground a few days after their cuticle has hardened. The eggs are laid by hearth and not evenly over the field. Densely overgrown areas are preferred to bare arable land. After about 4 weeks - depending on the temperature - the larvae hatch. These initially measure only 1.5 mm in length and are whitish in colour. The larvae develop over several years and, depending on the environmental conditions, they pass through a varying number of larval stages. In the course of the larvae skinning, longer periods of rest are repeatedly passed through.

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Control

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Damage
Damage

Wireworm damage was already considered a major problem in the old plant protection literature, which could only be overcome with difficulty. Despite intensive research efforts, it has not yet been possible to find a safe, environmentally friendly alternative to chemical measures. The severity of the damage caused depends on the part of the plant affected, the time of infestation and the number of older wireworms in the soil. In the case of pure root damage, seedlings (e.g. maize, probably due to late sowing) are most severely affected, while wireworms play a lesser role in cereals or are often not even noticed. The damage is greatest when the crop itself is affected, such as potatoes, carrots, onions, asparagus, radishes...

Although various research projects have found naturally occurring counterparts such as ground beetles and various insect-pathogenic fungi (Metarhizium anisopliae, Entomophthora elateridiphaga,...), it is still unclear whether they are suitable for biological control in practice. Work on biological control with the fungus Metarhizium anisopliae is being carried out at several institutions (e.g. Agroscope, Switzerland). However, experiments with insect-pathogenic nematodes or with the fungus Beauveria were not successful. Hunters have reported that the crop of killed pheasants was full of wireworms in autumn.

Measures

  • From the middle of the last century onwards, the wireworm problem was solved by the intensive use of chemical agents. At present, however, there are no longer any approved insecticides available for the cultivation of potatoes.
  • The fruit rotation measures are not very effective because the wireworms are very polyphagous and can live on various host plants. There is only agreement on the fact that after grassland uprooting there is a particularly high risk for the subsequent crop - this also applies to a lesser extent to fallow land. However, the situation is also complicated by the fact that there are several types of wireworms with different ecological requirements
  • Burning of cereal stubble fields reduces infestation - but is prohibited
  • intensive soil tillage (tiller) reduces infestation, but is bad for soil life
  • The use of the insect-pathogenic fungus Metarhizuim anisopliae is still in the experimental stage and is not yet ready for practical use.
  • Experiments on resistance of potato varieties to wireworms showed that resistance was related to the content of glycoalkaloids (solanine), which are, however, classified as toxic to humans.
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