Pests
Schizaphis graminum Rond. - spring grain aphid, greenbug.
Systematic position.
Class Insecta, order Homoptera, suborder Aphidinea, superfamily Aphidoidea, family Aphididae, subfamily Aphidinae, tribe Aphidini, subtribe Rhopalosiphina, genus Schizaphis.Biological group.
Oligophagous pests.Morphology and biology.
The body of apterous female is light green with longitudinal stripe along the dorsal side. The body length varies from 2.7 to 2.9 mm; the antenna is half as long as body length. Siphunculi are long (1.7-2 times as long as fingerlike tail), without swelling, light brown before the cover only. Siphunculi are cylindrical. Medial vein on front wing has only one branch. The oval eggs are black. The aphid life cycle includes one host-plant. Overwintering takes place in the egg phase on winter cereals, and also on cereal weeds. Sexual agamous generations are present. In areas where the pest is particularly harmful, fundatrices larvae hatch during the end of April, the beginning of May. The larval period lasts 8-15 days. The life span of the apterous parthenogenetic female is about 35 days. Female can produce as many as 80 larvae. The aphid feeds on winter cereals at first, and then on spring corn. Winged settling females appear at the end of May. The life span of winged parthenogenetic female is from 17 to 20 days. Fecundity approaches 42 larvae. The aphids feed on both lower and upper side of leaves. They form large colonies. Insect density increases quickly during the phase of plant elongation, and huge colonies can cover leaves completely. When the young growth of winter cereals appear, aphids migrate from summer reservations. At the end of September, beginning of October, vivparous individuals (virginoparae) are marked that give birth to females and males. Eggs are laid in October till early frost in groups of 2-4 eggs in leaf sheaths. The fecundity of female varies from 10 to 12 eggs, and the life span lasts 38-40 days.Distribution.
The insect is widespread in South Europe, Anterior, Middle, Central and Minor Asia, North and South America, West and South Africa, Japan. Within the territory of the Former Soviet Union the species occurs widely up to 56° N. It is most harmful in the steppe and forest-steppe zones, i.e., the North Caucasus, Volga Basin Region, Central Black Earth zone, Kazakhstan, Crimea, Ukraine.Ecology.
Maximum aphid numbers are observed at the end of June and in July. An aphid infestation is very dangerous when plants are at the phase of stem elongation. During the ripening of summer cereals, the number of aphids quickly decreases. The most favorable conditions for insects are temperatures of 20-21°C with a relative humidity of 65-70% for apterous females, and 25.8°C and 70% for winged females. The appearance of the sexual generation depends on the temperature and photoperiod. Within the territory of the Former Soviet Union the species can produce up to 15 generations during a year. Aphid populations can be particularly high after years with moist and damp summers.Economic significance.
The pest causes the greatest damage on summer and winter wheat, summer and winter barley, rye, oats, sorghum, millet, and rice. Among the wild cereal grasses it prefers Avena fatua L., Agropyrum repens P.B., Dactylis glomerata L., Bromus mallis L., and Setaria glauca L. Control measures include eradication of weeds and insecticide treatments at the end of May and in June. Insect population may be influenced by entomophages. The most important predators are Coccinella septempunctata L., C. notata Host., C. axiridis Pall., and also representatives of the genera Adalia, Semiadalia, Adonia (Coccinellidae); the genera Syrphus, Melanostoma, Scaeva, Eupeodes, Paragus (Syrphidae); C. carnea Steph., C. formosa Br. (Chrysopidae). The most important parasites are representatives of the family Braconidae (the genera Aphidius, Lysiphlebus, Ephedrus).Reference citations:
Bozhko M.P. 1950. On the fauna of aphids of Kharkov and Sumy Regions. In: Bulakin I.N., editor. Proceedings of Biological Research Institute of Khar'kov State University. V. 14-15. Khar'kov. 184-187 pp. (In Russian)Ivanovskaya O.I. 1977. Aphids of West Siberia. Part II, Novosibirsk: Nauka. 34-35 pp.
Moroshkina O.S. 1930. Spring grain aphid (Toxoptera graminum Rond.) (Biology, ecology, test of control treatments). Rostov-on-Don. 60 pp. (In Russian)
Radchenko E.E. 1991. The study of resistance of grain cultures to aphids (Methodical recommendations). Saint Petersburg: VIZR. 4-5 pp.
Shaposhnikov G.H. 1964. Suborder Aphidinea - aphids. Keys of Insects of the European Part of the USSR. Moscow & Leningrad: Nauka. V.1: 489-616.
Vasil'ev V.P., ed. 1973. The pests of agricultural crops and forest plantations. Kiev: Urozhai. V.1: 274-275.