The insect Rhopalosiphum maidis is known as the corn leaf aphid and is a vector for the viruses Maize Dwarf Virus (MDV) and Barley Yellow Dwarf Virus (BYDV). The resulting infection caused by either MDV or BYDV can result in significant crop losses, thus enhancing the importance of controlling this pest early in the season. Additionally, the nymph and adult feed on the whorls of the plant and the male inflorescence resulting in low pollen production and low yield.
The corn leaf aphid is small, measuring approximately 2 mm or less, with a bluish-green soft body and visible black legs. The aphid feeds through sucking mouth parts, leaving behind a sticky substance referred to as “honeydew,” which often becomes coated with a blotchy, sooty mould, aiding in identification of damaged plants. This sooty mould significantly adds to the potential damage produced by the insect, since the mould impairs photosynthesis, therefore affecting the productivity and overall health of the crop.
During scouting for the corn leaf aphids, examine 5 sets of 20 plants per field. If 50 percent of all plants during late-whorl to early tassel have more than 300 aphids per plant, under drought stress, immediate control is recommended.