Agriotes lineatus (L.)
Systematic position: Insecta, Holometabola, Coleoptera, Elateridae.
Common name: Lined click beetle.
Morphology: Adults about 9 mm in length, thorax and head almost black, their dorsum heavily punctuated. Elytra reddish-brown, hairy, with longitudinal lines, those at mid-elytra darker. Larvae initially whitish, turning light-brown, with darker intersegmental rings, head may be darker, body up to 15 mm in length.
Host plants: Polyphagous, feeding on many agricultural crops, with a preference for root crops, especially potato.
Geographic distribution: Most of Europe, Middle East, Asia, North and parts of South America, Haiti, and New Zealand.
Life history: This species prefers humid soil conditions along with relatively high temperatures.The adults appear in early spring, fly at night when temperatures are above 20ºC and are attracted to light. They place their eggs (100-300/female) in vegetation-covered humid soil. The emerging larvae, which are sensitive to dryness, initially feed on humus and then on under- and above-ground plant material. They may go through several (up to 12) instars. At maturity they pupate in the soil, to appear in the spring, sometimes dispersing by flying. Total development requires several years.
Economic significance: This polyphagous pest damages almost all agricultural crops, such as winter cereals, potato, beet, carrot, onion, alfalfa, clover, tomato, and fruit saplings. Most injury is due to feeding on germinating seeds and seedlings of winter crops, and penetrating into roots. Much injury is caused in fields that are periodically covered by standing or irrigation waters. Tomato seedlings, beet and carrot roots, and especially potatoes are heavily damaged. The larvae tunnel into potato tubers whereon they leave small, round holes on the surface and narrow tunnels that run into the flesh. About 20- 80% of the tubers may be affected, reducing their quality and rendering them unmarketable, even when damage is low. These holes also provides access for soil organisms, especially bacterial rots. On the whole, crops on lighter soils were consistently less damaged than those growing on heavier, more humid soils.
Management
Monitoring: Different methods are used for the monitoring of larvae and of adults. Larval presence and abundance (or absence) is monitored by within-field bait stations, the bait being placed in the ground and consisting of germinating cereal or other food seeds. Due to the prolonged larval development period (>3 years), trappings of one year-old larvae do not indicate the next years’ situation, thus necessitating long-term, several years’ trapping. Adult monitoring is with traps, baited with the Agriotes sex pheromone. However, as the beetles may disperse by flight, the obtained adults may have come from outside, which challenges the interpretation of these trap counts.
Horticultural methods: Continuous disturbance of the soil by plowing, crop rotation, growing less susceptible crops (like legumes) on infested fields and avoiding growing grasses and potatoes in such fields. Flooding during warm weather kills most larvae. Where potatoes are grown in infested fields, lifting them before the pests start to feed on the tubers.
Mass trapping: Beetle catches in pitfall traps placed inside and outside pheromone trapping zones significantly reduce male beetles
Plant resistance: Certain potato cultivars are less susceptible to the pest.
Chemical control: Seed dressing with a neonicotinoid, or applications of carbamates reduce wireworm damage but their level of control is inconsistent. The organophosphates Ethoprop caused almost 100% pest mortality. Due to the fact that the wireworms are generally not near the soil surface, the insecticides should be applied pre-planting or as a post-planting treatment.
Biological control: Numerous birds and beetles reduce wireworm numbers, however their rate of control is unknown. Infections with the entomophathogenic fungus Metarhizium brunneum Petch caused >80% pest mortality. Combining applications of this and other fungi with low insecticide concentrations increases their efficacy, but the long-term impact on subsequent pest numbers and damage reduction is not always clear. Likewise with Entomopathogenic nematodes.
References
Ansari, M.A.., Evans, M. and Butt, T.M. 2009. Identification of pathogenic strains of entomopathogenic nematodes and fungi for wireworm control. Crop Protection 28: 269-272.
Barsics, F., Haubruge, E. and Verheggen, F.J. 2013. Wireworms’ management: An overview of the existing methods, with particular regards to Agriotes spp. (Coleoptera: Elateridae). Insects 4: 117-152.
Blackshaw, R.P. and Hicks, H. 2013. Distribution of adult stages of soil insect pests across an agricultural landscape. Journal of Pest Science 86 (Special Issue): 53-62.
Danismazoglu, M. Demir, I., Sevim, A., Demirbag, Z. and Nalcacioglu, R. 2012. An investigation on the bacterial flora of Agriotes lineatus (Coleoptera: Elateridae) and pathogenicity of the flora members. Crop Protection 40: 1-7.
Ericsson, J.D.; Kabaluk, J.T.; Goettel, M.S.; Myers, J.H. 2007. Spinosad interacts synergistically with the insect pathogen Metarhizium anisopliae against the exotic wireworms Agriotes lineatus and Agriotes obscurus (Coleoptera : Elateridae). Journal of Economic Entomology 100: 31–38.
Johnson, S.N., Anderson, E.A., Dawson, G. and Griffiths, D.W. 2008. Varietal susceptibility of potatoes to wireworm herbivory. Agricultural and Forest Entomology 10:167–174
Kleespies, R., Ritter, C., Zimmermann, G., Burghause, F., Feiertag, S., Leclerque, A., 2013. A survey of microbial antagonists of Agriotes wireworms from Germany and Italy. Journal of Pest Science 86: 89-106.
Vernon W.G. and Verson, R.S. 2006. Effect of temperature and soil on the control of a wireworm, Agriotes obscurus L. (Coleoptera: Elateridae) by flooding. Crop Protection 25: 1057-1061.
Vernon, R.S., Blackshaw, R.P., van Herk, W.G. and Clodius, M. 2014. Mass trapping wild Agriotes obscurus and Agriotes lineatus males with pheromone traps in a permanent grassland population reservoir. Agricultural and Forest Entomology 16: 227-239.