There are many insects under the umbrella term of “leafhoppers” of which the two that are economically important to potato growers are the aster leafhopper (Macrosteles quadrillineatus) and the potato leafhopper (Empoasca fabae). These are pests throughout the US mid-west and southern Canada. Among entomologists, the leafhopper ranks third as the most important insect pest in North America, after the Colorado potato beetle and green peach aphid. Of the two leafhoppers above, the potato leafhopper has the most effect on yield reduction.
Aster leafhopper (Macrosteles quadrillineatus) damages crops not only through direct feeding on the sap but also by being a carrier for a disease “aster yellows.” Aster yellows is caused by a mycoplasma-like organism (MLO) or phytoplasma. These are similar to bacteria but lack a cell wall. They are not air or water-borne but must be transmitted through a carrier or vector.
Adult aster leafhoppers are wedge shaped and thin. They are a tenth to a fifth of an inch long. The bodies are a dull light green and there are six white spots on the top of the head and none on the thorax. The wings are silvery gray and fold back at rest. Like potato leafhoppers, nymphs are similar to adults but are smaller and wingless. Several nymphal stages occur in the generation.
Aster leafhoppers overwinter as adults in northern Texas, Oklahoma and Arkansas. They fly on winds north to Kansas, Nebraska, the Dakotas, Minnesota, and Wisconsin. It overwinters in grassy weeds and small grains. Overwintering as eggs has been reported.
The life cycle is similar to that of the potato leafhopper except that aster leafhoppers do not mate and lay eggs on potatoes. Adults live 30-40 days but may live as much as 90 days and as much as 200 eggs may be laid in an adult’s lifetime. Eggs hatch in ten days forming nymphs which convert to adults within a fortnight.
Injury by aster leafhopper feeding is minimal and not economically important. The problem rests in that it is a vector (carrier) of the ‘aster yellow mycoplasma-like organism’ (AY-MLO). This MLO causes ‘aster yellows’ also called ‘purple top.’ The MLO is acquired by the aster leafhopper from small grains not from potato. A large aster leafhopper population (severe population pressure) is needed for economic losses. However, yield reduction can occur. Most importantly is that potato tubers from infected plants with produce discolored potato chips and french fries during processing.
AY-MLO causes one disease that has many names including purple top and haywire. When as adult aster leafhopper first ingests the MLO, it takes 10 to 21 days for the MLO to replicate sufficiently to be able to be injected into potato plants. How the MLO causes the disease symptoms is not yet known. Flowers are most affected. Petals develop a green pigmentation and there is an abundant production of petals and sepals, both appearing like leaflets. Leaflets will be small, bunched and slightly rolled. A typical character of leaflets is a yellowing or reddening of the leaflet, hence, giving the descriptions of aster yellow and purple top. Aerial tubers and stem swelling around nodes are typically observed. Wilting may occur. Discoloration in potato chips is common. Harvested tubers may or may not be affected for seed. When affected, tubers produce spindly sprouts called hair sprouts. Symptoms vary widely and a laboratory identification is recommended.
Aster leafhopper does not pick up the MLO from potatoes.
Sustainable Agriculture — Monitoring fields for populations and correctly identifying the leafhopper is essential to good management as there are many leafhoppers that do not damage potato. There is no threshold established for aster leafhopper treatment.
Chemical Management — The same insecticides that affect potato leafhopper are effective against aster leafhopper.
The chief important host for aster leafhopper are small grains where they pick up the disease-causing MLO. Potato is not the preferred host of the aster leafhopper.
Quick Review / Aster Leafhopper
Adults - dull green, six white spots, 1/10-1/5 inch long
Nymph - like adult but smaller and wingless
Overwinters - Texas, Oklahoma and Arkansas
One to three generation/ season in north-central U.S.
Adults - June to early July
Adult - injects phytoplasma causing aster yellows feeding on sap (sucking-piercing insect)
Nymph - feeds off of the sap
Monitor and Identify
Economic Threshold = none established