Pests
Agriotes sputator L. - Common Click Beetle (Wireworm).
Taxonomic position.
Class Insecta, order Coleoptera, family Elateridae, subfamily Elaterinae, genus Agriotes.Biological group.
Polyphagous soil inhabiting pest.Morphology and biology.
Body length 6-9 mm, width 1.8-2.8 mm. Head in front is uniformly prominent, with dense punctures. Antennae reach apex of back angles of pronotum. Pronotum weakly prominent, having almost equal length and width, covered with dense fine punctures. Body black-brown, antennae and legs light ginger, fore edge of pronotum brownish-ginger. Elytrae fulvous or reddish-ginger with yellowish shade. Less often body coloration is black-brown, black, or reddish-ginger. Body of adult is covered entirely with dense grayish hairs. Larvae yellow, to 20 mm in length, to 1.5 mm in width, prolate and rigid. In their original habitus the larvae are usually called Wireworms. Mandible bears small tooth in the middle. The pest over-winters as adult and larva. Beetles are active from the end of April or May and from June in boreal areas. The period of adult activity lasts 1-2 months. Fecundity is 100 and more eggs. Eggs develop for 12-18 days. Depending on temperature and humidity, larval development lasts 2 to 4 years. Pupation occurs in July and August; pupae develop for 2-3 weeks. The entire developmental cycle of a generation lasts 3 to 5 years.Distribution.
Widely distributed in steppe and forest-steppe regions; occurs in the south of taiga. The geographic range covers the European part of the former USSR south of St. Petersburg; includes Crimea, the Caucasus and Transcaucasia, north Kazakhstan, south Siberia from the Ural Mountains to Transbaikalia, foothills of Alatau. Registered in the Far East (Shkotov district and south Sakhalin). Everywhere in Europe (except for the Far North), North Africa, Asia Minor, north Mongolia. Introduced into North America.Ecology.
Beetles appear when the soil heats up to 9-10°C. They lead a concealed mode of life, becoming active during the 2nd half of the day, weakly flying after sunset. Eggs are laid in soil in small groups at a depth of 2-5 cm, less often on soil surface, near plants as a rule. When moisture is lacking, the eggs fail to develop and die. Mass reproduction of the pest is connected to herbaceous plants, more often cereal grasses. Larvae eat seeds, sprouts, young caules, roots, seeking them by odor. Larvae are capable of surviving without nutrition for a long time, but they quickly die without contact water. Feeding begins at temperatures of 12°C. Freezing to -1.5°C causes cold catalepsy, at -4-6°C the larvae die within several hours. Searching optimum conditions, the wireworms make permanent movements. They rise to the warm upper layer of soil in early spring, descending to 1 m deep from the freezing upper layer during late autumn. Larval body is well adapted to movements in the soil, being smooth and firm. Cuneate head serves as digging organ, legs work as locomotor apparatus, and caudal appendage is used for fixation of body position and for reverse movements. The species is mesophilous, ecologically plastic. In the north of its range it inhabits open dry ecosystems, whereas in the south it develops under forest canopy and on irrigated territories. The greatest number of larvae is recorded on turfy-sandy, turf-podzol, humus carbonaceous, gray wooded, degraded and thick low-humic chernozem soils. Reduction of wireworm numbers is caused by birds (rooks, crows, starlings, etc.) during plowing, by parasitic and predatory insects (especially by ground beetles of the genera Carabus, Calasoma, Harpalus, Amara, etc.), and also due to diseases (bacterioses, fungal infections).Economic significance.
One of the most common harmful agricultural insect pests. Polyphagous, damaging almost all agricultural crops, especially grain cereals, maize, sunflower, peanut, beet, potato, and others including tree saplings. To a lesser degree it damages legumes (except for peanut), buckwheat, flax, mustard. It causes the maximaum harm by feeding on sown seeds and seedlings, eating nodes of tillering in cereals, and penetrating into roots. Control measures include thorough treatment of soil (removing of stubble and plowing, cultivation of fallow lands, inter-row treatment of cultivated crops), crop rotation, mineral fertilizing and dung application, weed (especially couch-grass) control, use of less susceptible cultures and varieties sown on fields heavily populated by wireworms, chemical treatment of seeds and application of soil insecticides, arrangement of poison baits on especially valuable fields. Pheromone traps are a prospective means for the purposes of forecasting; plant breeding for resistance to the pest is potentially effective.Reference citations.
Aleinikova M.M. 1962. Experience of ecofaunistic ranking in click beetles at Middle Volga region. Zool. Zhurn. v. 41 (7): 1028-1040. (in Russian).Cherepanov A.I. 1957. Click beetles of Western Siberia (Coleoptera, Elateridae). Novosibirsk: Novosibirsk Kn. Izd., 382 p. (in Russian).
Cherepanov A.I. 1965. Wireworms of Western Siberia. Moscow: Nauka. 191 p. (in Russian).
Dolin V.G. 1964. Larvae of click beetles (wireworms) of the European part of the USSR. Kiev: Urozhai, 207 p. (in Russian).
Dolin V.G. 1988. Click beetles. Cardiophorinae and Elaterinae. In: Fauna of Ukraine. Beetles. v. 19 (4). Kiev: Naukova Dumka, 204 p. (in Russian).
Gur'eva E.L. 1979. Click beetles (Elateridae). Subfamily Elaterinae. In: Fauna of the USSR. 12, 4. Leningrad: Nauka, 451 p. (in Russian).
Kryzhanovskii O.L., ed. 1974. Insects and mites as pests of agricultural crops. v. 2. Coleoptera. Leningrad.: Nauka, 335 p. (in Russian).
Shchegolev V.N., Znamenskii A.V., Bei-Bienko G.Ya. 1934. Insects harming to field crops. Leningrad - Moscow: OGIZ - Sel'khozgiz, 464 p. (in Russian).