Recent information called my attention to the geographic expansion of an invasive pest affecting grasses and cereals. This new pest is the old world aphid Sipha maydis (Hemiptera: Aphididae). The first report on S. maydis came from John Sorensen (California Department of Food and Agriculture), who confirmed the presence of this aphid in nursery samples of giant wild rice (Leymus condensatus) in 2007. Later, this aphid was reported on wheat in a greenhouse in Georgia in 2012; and in fall of 2014, Dr. Tessa Grasswitz found the aphids in Colorado feeding on oats used as a cover crop (EntomologyToday). In February and March of 2015, S. maydis was reported on annual grasses and wheatgrass in Colorado, and later in wheat in Alabama. The latest finding of S. maydis was on rye cover crop and wheat in April 2016 in South Carolina.
This species is reported throughout the Mediterranean region, into Central and South Asia, and South Africa. In addition, it has been intercepted on several occasions on imported plants in Florida and California, a clear indication that increased international trade contributes to the introduction of invasive species. In the New World, this aphid has caused great economic losses on wheat in Argentina since 2002.
Although this aphid species is apparently having a slow pace of geographical dispersion, it is important to put attention to the possible colonization of new areas by this aphid. Extension agents, growers, consultants, and researchers should become aware of the presence of this insect, so preventive measures to control this invasive species can become more efficacious as soon as the target insect is identified.
Sipha maydis is recognized easily by its black color and completely sclerotized (hardened) dorsal part (upper side or back), and spinous body setae (Figure 1).
It feeds on a range of grass hosts, including wheat, oats, barley, johnsongrass, sorghum, and corn, and it is recorded on more than 30 grasses or cereal species.
Symptoms of Damage
Sipha maydis feeding causes damage to leaves. It feeds on the upper surfaces of leaf blades near the bases, and sometimes on stems and inflorescences, where it may be ant-attended. Heavily infested leaves may become yellowed, rolled into tubes, and desiccated (Sorensen, 2013). Sipha maydis is also a vector that can transmit cucumovirus (cucumber mosaic) and luteovirus (barley yellow dwarf).
By Raul Villanueva, Extension Entomologist