Yellow Sugarcane Aphid: Sipha flava (Forbes)
Description and Biology: The yellow sugarcane aphid is usually lemon yellow but under some conditions is pale green, 2 mm long, covered with small spines, and has two double rows of dark spots on its back. Cornicles are very short. Winged and wingless forms live in the colony. The wide range of wild hosts includes johnsongrass and dallisgrass, Paspalum dilatatum Poir. Without mating, females give birth for 28 days to living young. Each female produces an average of two nymphs per day. Nymphs mature in 13 to 19 days.
Symptoms and Damage: Yellow sugarcane aphids feed on the underside of lower sorghum leaves and inject toxin into leaves of seedlings and older plants. Feeding aphids cause purple-colored leaves on seedling sorghum and yellow leaves on more mature plants. Plants not killed are severely stunted and even slightly damaged plants have delayed maturity. By the time discoloration symptoms are visible, plants have been injured significantly. Very few aphids on a plant, especially a seedling can cause severe damage. Damage often causes plant lodging that may be enhanced by associated stalk rots.

Monitoring: The presence of yellow sugarcane aphids must be determined soon after sorghum plants emerge. Often the severity of yellow sugarcane aphids can be determined at planting time by the abundance of these aphids on nearby johnsongrass and dallisgrass. The presence of purple-colored seedling plants is a possible indication of a yellow sugarcane aphid infestation, however purple leaves also can be caused by weather conditions and other factors. Sorghum should be scouted and plants inspected beginning the first week of plant emergence and twice weekly until plants have at least five true leaves. Yellow sugarcane aphid injury to sorghum is most severe when plants are small. As plants grow larger, they become more tolerant to aphid feeding. Very small seedling sorghum plants (one to three true leaves) often are significantly damaged after being infested for a week or less. An insecticide application would be justified when ten to forty percent of plants are infested at the one- to three-leaf stages.

Management: Many predators feed on the yellow sugarcane aphid, but the aphid rarely is parasitized. Planting at a time when conditions are favorable for rapid seedling growth is important as larger plants are less damage than smaller plants. Several foliarly applied insecticides effectively control yellow sugarcane aphids in sorghum, if applied soon enough after infestation occurs. Some systemic insecticides applied to seed or in furrow at planting will also control yellow sugarcane aphid.

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