Pests
Oulema melanopus (Linnaeus) - Red-throated Cereal Leaf Beetle, Barley Leaf Beetle
Systematic position.
Class Insecta, order Coleoptera, family Chrysomelidae, subfamily Criocerinae, genus Oulema. Records of the species from the Far East (on rice) belong to O. oryzae Kuw.Synonym.
Lema melanopus L.Biological group.
Oligophagous pest of cereals.Morphology and biology.
Beetle greenish blue with metallic shine (body length 4-5 mm). Pronotum and legs yellow-red; apices of femora, tarsi, and antennae black; elytra have parallel rows of punctures. Egg amber-yellow, black when mature, cylindrical, rounded at apices, covered with sticky substance that hardens in the air. Larva 5-6 mm in length, wrinkled, bent, thickened in the middle, covered with brown slime, resembling a small leech. Pupa yellowish, darkening later, covered with transparent pellicle. Imagoes winter in ground. In spring, they settle crops of summer cereals. Fertility is 120-300 eggs. Female lays eggs more often on the lower side of glabrous leaves of cereals, on average 5-7 eggs in a chain. Larvae appear after 10-14 days. Larva has 4 instars, developing over 2-3 weeks. Adult larva clears from its mucous cover, abandons plant, and arranges pod-like cradle in the upper layer of ground, where it pupates. In two weeks, the beetle appears. Young beetles remain in cocoons until spring of the next year.Distribution.
The Cereal Leaf Beetle inhabits Europe (everywhere), North Africa, Asia Minor, Mongolia, and North America (adventive). In the former USSR, it is distributed everywhere, except for in the Far North, the desert zone, and the Far East.Ecology.
Monovoltine species. In spring, the beetles appear on ground surface when daily average air temperatures reach 7.5-9.0°C, i.e., at the end of April or in the beginning of May in the European part of the former USSR, in March or April in Central Asia. In the beginning, the beetles feed on wild-growing cereals, then on fields of winter grain crops, and further on summer crops. Feeding on crops, pairing and laying eggs, the beetles stay in groups, therefore damaging crops in places. They fly most intensively in warm, sunny weather from 10-11 a.m. The pest is especially dangerous when humidity is low. Within Eastern Kazakhstan and the Gorno-Altay Republic of Russia, the degree days sum for development of one generation of the species is 431.5°C. Optimum conditions for egg and larvae development are temperatures of 23-25°C and a relative humidity of 60-70%. The most vulnerable stages of the Cereal Leaf Beetle development are eggs and larvae of 1st instar.Economic significance.
Beetles gnaw out longitudinal apertures in leaves; larvae skeletonize leaves of oats, barley, hard varieties of summer and winter wheat, rye, maize, rice, and many species of wild-growing cereals. Larvae eat pulp of leaves, leaving veins. Larvae of 3rd-4th instars cause the most essential harm. The damaged leaves are distinguished from green ones by whitish, longitudinal stripes. Large numbers of larvae cause coalescence of damaged parts, and the entire leaf turns yellow. Harming activity of the species proceeds from tillering until ear emergence. The maximum fertility of the Cereal Leaf Beetle occurs in droughty years. Lack of ground moisture causes beetles and larvae to have a stronger influence on plants, i.e. yield is reduced, and the weight of 1000 grains decreases. Strongly damaged plants do not form ears during droughty weather. Control measures: Agronomical measures include early sowing of summer cereals and the selection of resistant varieties; chemical measures include insecticide treatments in spring during feeding of larvae and beetles and treatments of field edges.Related references.
Belyaev I.M. 1974. Pests of grain crops. Moscow: Kolos. 284 p. (in Russian).Brovdii V.M. 1974. Family Chrysomelidae. In: Vasil.ev V.P., ed. Pests of agricultural crops and forest plantations. V.2. Kiev: Urozhai, p. 49-88 (in Russian).
Dobrovol.skii B.V. 1959. Distribution of insect pests. Foci and zones of maximum harm. Moscow: Sovetskaya nauka, 216 p. (in Russian).
Guslits I.S., Shapiro I.D. 1978. Cereal Leafbeetle. In: Shapiro I.D., ed. Methodical recommendations on evaluation of agricultural crops resistance to pests. Leningrad: VIZR, p. 79-97 (in Russian).
Lopatin I.K., Medvedev L.N., Shapiro D.S. 1974. Family Chrysomelidae. In: Kryzhanovskii, O.L., ed. Insects and mites - pests of agricultural plants. V. 2. Coleoptera. Leningrad: Nauka, p. 157-197 (in Russian).