Pests
Chaetocnema aridula Gyll., Chaetocnema hortensis Geoffr. - Cereal Stem Flea Beetles.
Systematic position.
Class Insecta, order Coleoptera, family Chrysomelidae, genus Chaetocnema Steph.Biological group.
This species is a pest of cereal crops.Morphology and biology.
C. aridula is larger (body length is 2.5-3 mm) than C. hortensis (1.6-2.3 mm). Elytra bronze brown or bronze coppery, sometimes cyan in color. Elytron of C. hortensis with regular rows of punctures along side and in apical part. Elytron of C. aridula with mixed or double irregular rows of punctures laterally. Hind femur thickened, adapted for jumping. Adults emerge in March-April after hibernation in forest belts, in sods of wild gramineous plants, and then they fly to winter cereal fields. Beetles migrate to spring cereals after shoot appearance. Lower temperature threshold for development is 5 degrees C. Adults do not cause much damage, they usually eat parenchyma on wilting leafs. C. aridula lays eggs on root leaves, but C. hortensis lays them in the soil around shoots. Hatching larvae bore into stem and develop there before pupation. Stem does not produce ear after infestation, and sometimes is destroyed; flag leaf turns yellow and wilts. Larva develops in 14-22 days. Body of larvae of both species are cylindrical, light in color, with scattered brownish spots, black head and 3 pairs of legs. Body length of last instar larva is up to 5 mm. Larva moves out of the stem into soil for pupation. Young adults emerge at the end of June-August. Hibernation begins after additional feeding on spring cereals, on drop of cereals, and on weeds.Distribution.
Both species have a Transpalearctic area. C. hortensis is widely distributed throughout the former USSR from the European part to the Primorskii Territory, in the Caucasus, in Kazakhstan and Middle Asia. C. aridula has the same distribution, being perhaps absent in Turkmenistan, Tajikistan and Uzbekistan.Ecology.
C. aridula and C. hortensis are eurytopic polyzonal species, inhabiting territories from taiga to steppe, being absent in the Subarctic region, deserts and semi-deserts. Outside agrocenosis both species develop on wild gramineous plants including couch-grass. They are monovoltine in most areas and perhaps bivoltine in the southern regions.Economic significance.
Losses of harvest caused by both pests can reach 10-15%. Main shoot infested at the end of tillering stage is destroyed, but it produces ears without kernels during the stem elongation stage. Secondary tillers are destroyed after infestation, or they survive, but don't produce ears.Reference citations:
Dobrovol'skii B.V. 1951. Harmful beetles. Rostov-na-Donu: Rostizdat. 455 p. (In Russian)Dubeshko L.N., Medvedev L.N. 1989. Ecology of leaf beetles from Siberia and Far East. Irkutsk: Irkutsk University. 224 p. (In Russian)
Konstantinov A.S. 1988. Landscape-zonal peculiarities of the Chaetocnema beetles distribution (Coleoptera, Chrysomelidae). Vestnik Zoologii, 6: 44-47. (In Russian)
Kopaneva L.M., ed. 1980. Keys to harmful and useful insects and ticks on the grain plants in the USSR. Leningrad: Kolos. 335 p. (In Russian)
Lopatin I.K. 1977. Leaf beetles (Chrysomelidae) from Middle Asia and Kazakhstan. Leningrad: Nauka. 289 p. (In Russian)
Lopatin I.K., Kulenova K.Z. 1986. Leaf beetles (Coleoptera, Chrysomelidae) from Kazakhstan. Alma-Ata: Nauka. 199 p. (In Russian)
Palii V.F. 1961. Fauna of pest flea beetles from the USSR. Frunze: AN Kirgiz. SSR. 101 p. (In Russian)
Putele V. 1970 a. Fauna of flea beetles from Latvian SSR. Materials of 7th Baltic meeting on plant protection, part 2. Pests of agricultural and forest plants and their control. Elgava: Latvian Ministry of Agriculture. 17-20 p. (In Russian)
Putele V. 1970 b. Flea beetles of the genus Chaetocnema from Latvian SSR. Materials of 7th Baltic meeting on plant protection, part 2. Pests of agricultural and forest plants and their control. Elgava: Latvian Ministry of Agriculture. 20-25 p. (In Russian)
Shchegolev V.N., ed. 1955. Agricultural Entomology. Leningrad-Moscow: Sel.khozgiz. 616 pp. (In Russian)
Shutak V.I. 1973. Numerous pests of the flea beetles from the Bashkiria and South Cis-Ural. Science for production (collection of works). Voronezh: Minsel.khoz. 85-88 p. (In Russian)
Timokhina A.F., Sobakar' T.A. 1991. Stem flea beetles and their influence for harvest of spring wheat. Forecast and integrated control of pests, diseases and weeds of agricultural plants (collection of scientific works). Novosibirsk: Sibirskoye otdeleniye RASKhN. 17-23 p. (In Russian)