Rhopalosiphum padi (L.)
Taxonomic placing: Insecta, Hemimetabola, Hemiptera, Sternorrhyncha, Aphidoidea, Aphididae.
Common name: Blue berry oat aphid, choke-berry oat aphid.
Geographical distribution: Cosmopolitan; CIE Map #289, 1971.
Host plants: The primary hosts are Prunus spp., and the secondary hosts are many (about 100) species of Poaceae (Graminae), Cyperaceae and Typhaceae.
Morphology: The body of the apterous females is about 2.5 mm long, green-brown. The head, siphunculi (which are swollen) and cauda are brown-black. The alate females are mostly green, siphunculi brown, body length about 2.4 mm.
Life cycle: In the Middle East this aphid reproduces only by viviparous parthenogenesis on various Poaceae, like maize, barley, oats and wheat, each female producing 40-60 progeny on the various hosts. It can complete a cycle within the range of 12-28ºC, the optimum for development and fecundity being around 24ºC. In colder regions alates appear during autumn and fly to Prunus spp. (P. padus L. in Europe). There they produce sexual forms which mate and lay winter eggs that remain dormant till spring. The emerging aphids feed on Prunus foliage for 2-3 generations and, in mid-summer, migrate to Poaceae, locating them by host volatiles.
Economic importance: Feeding on spring cereals, especially corn (maize), causes their leaves to roll and can result in about 15% yield losses. In addition, the excreted honeydew, colonized by sootymold, reduces photosynthesis. However the main damage caused by this aphid by being the main vector of barley yellow dwarf virus (BYDV), a major disease of barley, oats and wheat. When feeding on Prunus pardu its leaves become twisted to form gall-like structures in which the aphids hide.
Management
Monitoring: Suction traps are used for establishing aphid arrival in summer. Another method, developed in Denmark, consists of counting aphids on the susceptible crops and expressing the result as aphid-days, number of aphids/tiller multiplied by the number of days that they are present. A control threshold of 105 aphid-days was thus established. A similar method is the older control threshold at about 10 aphids/tiller.
Horticultural methods: The destruction of volunteer cereals and overwintering stubble, in which aphids may hide, before preparing the field for a new crop. Intercropping with none-graminaeous crops.
Plant resistance; Varieties of graminaeous crops that are resistant to the aphid and/or virus have been developed.
Molecular methods: Transgenic wheat plants expressing resistance to BYDV reduce the production of volatiles, making virus-infected plants less attractive to the aphids as compared to untransformed infected plants. Feeding on transgenic maize plants that express the Bacillus thuringiensis toxin had no effect on R. padi.
Chemical control: In colder regions seeds of winter cereal treated with imidacloprid can protect against aphid and BYDV. Threshold numerical values for forecasting and spraying are now commonly used, so that insecticides will only be used during significant infestations. As the aphid is only a minor pest in the Middle East, chemical control is seldom needed.
Biological control: Predation by Bembidion lampros (Herbst) and Pterostichus cupreus Linnaeus (Carabidae) on the aphids as they arrive at cereal fields sometimes prevented pest outbreaks in Sweden. In Israel and elsewhere the pest is parasitized by several Aphidiidae, but their effects are not known. Various entomopathogenic fungi infect the aphid in different regions. Verticillium lecanii (Zimmerman) Viegas (now in the genus Lecanicillium) and Neozygites fresenii (Nowakowski) Batko are the more prevalent species, sometimes greatly reducing pest numbers.
References
Auad, A.M., Alves, S.O., Carvalho, C.A., Silva, D.M., Resende, T.T. and Veríssimo, B.A. 2009. The impact of temperature on biological aspects and life table of Rhopalosiphum padi (Hemiptera: Aphididae) fed with signal grass. Florida Entomologist 92: 569-577.
Ekbom, B.S., Wiktelius, S. and Chiverton, P.A. 1992. Can polyphagous predators control the bird cherry-oat aphid (Rhopalosiphum padi) in spring cereals? Entomologia Experimentalis et Applicata 65: 215–223.
Finlay K.J. and Luck, J.E. 2011. Response of the bird cherry-oat aphid (Rhopalosiphum padi) to climate change in relation to its pest status, vectoring potential and function in a crop–vector–virus pathosystem. Agriculture, Ecosystems and Environment 144: 405–421.
Gourmet, C., Hewings, A.D., Kolb, F.L. and Smyth, C.A. 1994. Effect of imidacloprid on nonflight movement of Rhopalosiphum padi and the subsequent spread of barley yellow dwarf virus. Plant Disease 78: 1098-1101.
Hansen, L.M. 2000. Establishing control threshold for bird cherry oat aphid (Rhopalosiphum padi L.) in spring barley (Hordeum vulgare L.) by aphid-days. Crop Protection 19: 191-194.
Hesler, L.S., Riedell, W.E., Kieckhefer, R.W., Haley, S.D. and Collins, R.D. 1999. Resistance to Rhopalosiphum padi (Homoptera: Aphididae) in wheat germplasm accessions. Journal of Economic Entomology 92: 1234-1238.
Jiménez-Martínez, E.S., Bosque-Pérez, N.A., Berger, P.H., Zemetra, R.S., Ding, H. and Eigenbrode, S.D. 2004. Volatile cues influence the response of Rhopalosiphum padi (Homoptera: Aphididae) to barley yellow dwarf virus-infected transgenic and untransformed wheat. Environmental Entomology 33: 1207-1216.
Lozzia, G.C., Furlanis, C., Manachini, B. and; Rigamonti, I.E. 1998. Effects of Bt corn on Rhopalosiphum padi L. (Rhynchota: Aphididae) and on its predator Chrysoperla carnea Stephen (Neuropter:a Chrysopidae). Bolletino di Zoologia Agraria e di Bachicoltura, Ser. II, 30: 153–164.
Nielsen, C. and Steenberg, T. 2004. Entomophthoralean fungi infecting the bird cherry-oat aphid, Rhopalosiphum padi, feeding on its winter host bird cherry, Prunus padus. Journal of Invertebrate Pathology 87: 70-73.
Swirski, E. and Amitai, S. 1999. Annotated list of aphids (Aphidoidea) in Israel. Israel Journal of Entomology 33: 1-120.
Taheri, S., Razmjou, J. and Rastegari, N. 2010. Fecundity and development rate of the bird cherry-oat aphid, Rhopalosiphum padi (L.) (Hom.: Aphididae) on six wheat cultivars. Plant Protection Science 46: 72-78.