Agriotes  spp.

( Wireworms )

General  

• insects Beetle distributed in several genera. The genus Agriotes most present in France has around 200 species.
• Their larvae ("wireworm") cause most of the damage parasitizing many vegetable crops, especially the last larval stages.
• Differentiate according to the length of their cycle:
  • Long-cycle species (5 years, including 4 years as larvae in the soil) ( Agriotes lineatus , Agriotes obscurus and Agriotes sputator ).
  • Short-cycle species ( Agriotes sordidus ) (usually a 2-year cycle but up to 4 years depending on soil temperature and climatic conditions).
• Sensitive crops : potatoes, carrots, beets, turnips, salads, asparagus, strawberries, garlic, onions, etc. Damage to eggplant is less frequent.
• Organs attacked  : young seedlings, low part of the stem, fruits more or less  in contact with the ground.

• Symptoms :
  • More or less narrow and deep perforations and galleries observed on the organs and on some seedlings.
  • Poor growth, loss of vigor of plants.
  • Wilting, dieback of seedlings and plants.
  • Depreciation of fruit quality, even loss of harvest.

• Signs  : Presence of "wire" larvae in or near tissue.
• Possible confusion :

Biology

• Development cycle : usually very long, can last more than 4 years as larvae in the soil. After pupation, in the fifth year, the adult emerges from the ground, and after having mated, will lay eggs in the plant litter.
  • Females lay their eggs in the soil, at a depth varying from 20 to 60 mm, preferably in moist or cool soils rich in organic matter. The eggs are slightly oval and can reach 0.5mm in length.
  • After hatching, the larvae move vertically in the soil depending on its humidity, temperature. Not tolerating drought, they rise during wet periods and fall again during dry periods, with activity stopping in summer and winter. At least eight larval stages can be observed. The larvae resemble worms, have 3 pairs of legs and a rigid, well-segmented shell. They are elongated, straw-yellow in color, with a flattened brown head, and can measure from 2 to 25 mm in length.
  • Pupation occurs in the soil.
  • The adults overwinter in the soil. They are very mobile, appear in spring and only live for a few months, often in sheltered areas (woods, hedges, even meadows). They fly very little, but walk actively, with nocturnal activity. They consume the leaves of the most varied wild or cultivated plants. Their color varies from brown-black to yellow and measure 6 to 12 mm.

Protection

• Carry out crop rotations, crucifers are not favorable to the development of wireworms, sunflowers are considered less appetizing.
• Avoid too much organic manure.
• Bring lime (wireworms do not like calcareous soils).
• Superficially scratch the soil of loose plots in spring and early summer and allow it to dry.
• Summer plowing makes it possible to reduce the larval populations by 30 to 70%.
• Drizzle regularly with a dilute solution of fern manure.
• Trap insects using pheromone traps.
• Reason for chemical protection, in particular if you use auxiliaries.
• Use biopesticides.