Pests
Rhopalosiphum maidis Fitch - Corn Leaf Aphid
Systematic position.
Class Insecta, order Homoptera, suborder Aphidinea, superfamily Aphidoidea, family Aphididae, subfamily Aphidinae, tribe Aphidini, subtribe Rhopalosiphina, genus Rhopalosiphum.Biological group.
Oligophagous pests of cereals.Morphology and biology.
The ovoid body of apterous female is gray-green or white-green. Head, legs, siphunculi, tail, and transversal stripes on 7-8 abdominal tergites are black. Antenna is 2 times shorter than half-length of body, without secondary rinariums. Beak reaches to mid coxae. Cylindrical siphunculi are short (not longer than fingerlike tail), with a swelling at apex and with a constriction. Marginal tubercles are small. Winged virgin female has brown-black head, thorax, antenna, legs, siphunculi, and tail; yellow-green abdomen with brown marginal plates; antenna with secondary rinariums on segments 3-5. Siphunculi in winged female are shorter, than those in apterous female. Medial vein on fore wing is bifuracated; second branch is very short, beginning near the wing margin. Oval eggs are black. Both eggs and imagoes (apterous parthenogenetic females) overwinter on cereal grasses. In the latter case, the insect has anholocyclic development. In the zone of high harmfulness, the hatching is observed at the middle of April. At first, aphids feed on perennial cereal grasses, then on winter and spring cereals, situating in axils of upper leaves (on lower side); they feed also on stems and ears. The plants do not produce ears during the mass aphid multiplication. The aphid migration to maize takes place at the end of May - beginning of June. Biggest colonies populate tassels and leaves of upper layer, but small colonies are marked also on leaves of middle and lower layer. At tassel fading, the number of aphids decreases essentially. Only small colonies of the pest are observed from the end of July to middle of August. The number of aphids increases again at the end of August. During that period, insects feed on ears. Larval period lasts 6-8 days. Life span of apterous parthenogenetic female is 20-30 days and more, its fecundity reaches 30 larvae. From the beginning of September to November the insects migrate to winter cereals and wild grasses for wintering.Distribution.
The Corn Leaf Aphid is spread in South Europe; Anterior and Middle Asia; North America; also in the territory of the Former Soviet Union.Ecology.
Mass populating of maize by the Corn Leaf Aphid is marked from the end of June to the end of second third of July. The most favorable conditions are the temperature 28-32°C and relative humidity 60-70%. At the temperature 15°C, the development of population is essentially delayed. The species gives 10-12 generations during a year. Most important predators are Chrysopa californica Coq., Ch. lanata Bks., Ch. plorabumpunctata Fitch., Adalia bipunctata L., Coccinella arcuata F., C. septempunctata L., Coelophora inaequalis F., Cycloneda sanguinea L., Cydonia lunata F., C. vicina Muls., Scymnus constrictus Muls., Phaenobremia meridionalis Felt., Allograpta fracta O.-S., A. oblique Say., A. venusta Curr., Baccha clavata F., Syrphus vitripennis Meig., Aphidius exiguous Hal, A. platensis Brethes, Lysiphlebus testaceipes Cress., Aphelinus maidis Timberl., A. semiflavus How.Economic significance.
The pest feeds on wheat, barley, rye, oats, maize, millet, sorghum, sugar-cane, and wild cereals. On cereals, the insects damage leaves and ears; sometimes, the plants do not give ear. On maize, the damage of tassels and grains are the most dangerous. Injured leaves become yellow and twisted. The aphids pollute the leaves by frass, causing the development of fungal diseases. High harming activity appears in steppe and forest-steppe zones of Russia, in Ukraine, Transcaucasia, North Caucasus, Kazakhstan (in some regions), Moldova, Middle Asia, Crimea. Control measures include eradication of weeds, insecticide treatments when needed.Reference citations:
Abashidze F.T. & Tvalavadze Yu.I. 1966. Materials of Aphis maidis Fitch studying on maize and its control. In: Kanchavelli L.A., ed. Proceedings of Georgian plant protection institute, N 18. Tbilisi: MSKh GSSR, p. 69-70 (in Russian).Berry R.E. 1969. Effects of temperature and light on takeoff of Rhopalosiphum maidis and Shizaphis graminum in the field (Homoptera: Aphididae). Annals of the Entomological Society of America, 62(5): 1176.
Cartier J.J. 1957. On the biology of the Corn Leaf Aphid. Journal of Economic Entomology, 50(1): 116.
El-Ibrashy M.T., El-Ziady S. & Riad A.A. 1972. Laboratory studies on the biology of the corn leaf aphid, Rhopalosiphum maidis (Homoptera: Aphididae). Entomologia experimentalis et applicata, 15(2): 924-932.
Elliott N.C., Kieckhefer R.W. & Walgenbach. 1988. Effect of constant and fluctuating temperatures on developmental rates and demographic statistics for the corn leaf aphid (Homoptera: Aphididae). Journal of Economic Entomology, 81(5): 1383.
Everly R.T. 1960. Loss in corn yield associated with the abundance of the corn leaf aphid Rhopalosiphum maidis in Indiana. Journal of Economic Entomology, 53(5): 924.
Fedorov M.S. 1958. Aphids - pests of maize in Transcaucasia. In: Salmin I.G., ed. Proceedings of Stavropol' agricultural institute, N 8. Stavropol': Stavropol' agricultural institute, p. 150-160 (in Russian).
Foott W.H. 1977. Biology of the Corn leaf aphid, Rhopalosiphum maidis (Homoptera: Aphididae), in southwesteren Ontario. The Canadian Entomologist, 109(8): 1129-1137.
Ivanovskaya O.I. 1976. Fauna of aphids on the territory of West Siberia. In: Zolotorenko G.S., ed. Fauna of helminthes and arthropods of Siberia. Novosibirsk: Nauka, p. 175-189.
Muddathir K. 1976. Studies on the biology of wheat aphids in the Gezira (D.R.Sudan). Beitrage zur Entomologie, 26(2): 464-470.
Nevskii V.P. 1929. Aphids of Middle Asia. Proceedings of Uzbekistan Experimental plant protection station (Tashkent) 16: 186 (in Russian).
Shaposhnikov G.Kh. 1964. Suborder Aphidinea . aphids. In: Bei-Bienko G.Ya., ed. Keys to insects of the European part of the USSR. V. 1. Moscow & Leningrad: Nauka, p. 568 (in Russian).
Shaposhnikov G.Kh. 1972. Order Homoptera - homopterous. In: Kryzhanovskii O.L., ed. Insects and mites - pests of agricultural crops. V. 1. Leningrad: Nauka, p. 160 (in Russian).
Singh S.R. & Painter R.N. 1964. Effect of temperature and host plants on progeny production of four biotypes of Corn Leaf aphid, Rhopalosiphum maidis. Journal of Economic Entomology, 57(3): 348.
Sumarokov A.M. 1978. Dynamics of corn leaf aphid on maize. In: Susidko P.I., ed. Proceedings of III research conference for young scientists on maize problems. Dnepropetrovsk: Institute of Maize, p. 186-187 (in Russian).
Sumner L.C., Eikenbary R.D., Johnson R.C. 1986. Survival and reproduction of Rhopalosiphum maidis (Fitch) (Homoptera: Aphididae). Journal of the Kansas Entomological Society, 59(31): 561- 563.
Tsintsadze N.K. 1969. To study of geographical and vertical distribution of corn aphid in Georgia. In: Ul'yanishchev V.I., ed. Proceedings of Session of Transcaucasian Board to coordination research works on plant protection. Baku: Elm, p. 163 (in Russian).
Vasil.ev V.P., ed. 1973. Pests of agricultural crops and forest plantations. V. 1. Kiev: Urozhai, p.273-274 (in Russian).