Insect Note #36 (Revised)

Prepared by:
Kenneth A. Sorensen, Extension Entomologist

Dated 2/94
Placed on the Web 4/95 by the Department of Entomology, NCSU

Asparagus Aphid

Homoptera, Aphididae: Brachycolus asparagi Mordvilko

The asparagus aphid, native to Europe, was first reported in New York in 1969, in North Carolina in 1976, and in Washington in 1979. Although this aphid is capable of causing serious stand reductions and significant losses in yield, its economic impact has not been well defined.

Distribution

The asparagus aphid is native to Eastern Europe and the Mediterranean area. In North America, it has been reported from Massachusetts, Rhode Island, New York, Michigan, Washington, British Columbia, California, Oregon, New Jersey, Pennsylvania, delaware, Maryland, Virginia and North Carolina. This aphid appears sensitive to relative humidity and rainfall, with populations increasing under conditions of low rainfall and relative humidity. Hence, the distribution and the establishment of the asparagus aphid are dependent on man's movement of crowns, local weather conditions, and natural factors.

Hosts

All life stages of the aphid occur on asparagus and no alternate hosts appear necessary to complete the life cycle. Ornamental asparagus species are not known to serve as hosts.

Economic Importance

Asparagus aphids feed on cladophylls (modified leaves) and under bracts. Most activity occurs on terminal fern growth in the axils where the needles join the stem. Within three to seven days following feeding, the growth between stem nodes decreases, giving leaves and affected stems a tufted appearance. Heavily infested seedlings may form rosettes, shrivel or die. Damage on plants less than three years of age is severe as plants may be killed directly. On older plants considerable damage or dwarfing may also result. Of additional concern is the indication that crowns of older plants infested with aphids the preceding year show a decaying condition with no buds present. Though the roots appeared healthy, the crown was technically dead. Hence, it is most important to keep this perennial plant in a viable state from year to year if maximum yields are to be produced. Heavily infested plants are easily noticed due to the presence of severely stunted, blue-gray shoots around the base of the plant. This "Bonsai effect" is also seen throughout the fern. Drops of honey dew and, at times, the presence of lady beetles also indicate the presence of aphids.

Description

Winged and wingless aphids are small (1 mm) and powdery gray-green to green in color. The cornicles (exhaust tubes) are very short or reduced. Eggs are shiny green when first laid and turn black within a few hours.

Life History

The aphid passes the winter in the egg stage. These eggs are laid singly on stems under bracts around the base of the plants. Eggs hatch in the spring and first instar nymphs feed on the spears as they emerge from the ground. Aphids have four instars or life stages and pass the summer as nymphs and females which give birth to living young. Winged or wingless forms are produced throughout the summer with the first winged aphids appearing in May. There are many generations throughout the growing season. As fall yellowing of the plants occur; winged males are formed, mating occurs, and eggs are laid (around November 1).

Control

Infestations often result from the planting of infested crowns. Hence, certified crown producers should isolate their fields from commercial plantings. A minimum distance of 10 feet is recommended but a mile is preferred. Growers should also closely check plants in September and October for aphid colonies and treat when colonies are observed. Regular sprays of malathion 57EC at 2 pints/acre (1 tablespoon/gallon for homeowners) for asparagus beetles is of some help against aphids. The overuse of carbaryl (Sevin) for other insect pests of asparagus should be discouraged, as aphids build when relieved of their natural enemies.

Di-Syston 8EC at 1 pint in a minimum of 10 gallons of water/acre is registered. Applications may be needed in August and September. There is a 5 1/2 month interval to harvest with a maximum of 3 applications/season.

Early season (March, April) fern management may be important in the integrated control of the asparagus aphid. If early season ferns are not permitted to grow during the period from egg hatch to first generation females, aphids may not get established. In addition, the removal of all spears during this period appears to lessen the "Bonsai effect" through simple dilution of the aphid toxin.

Asparagus aphids appear to be attacked by at least 31 species of natural enemies (predators, parasites and diseases). As a result, asparagus aphid buildup should be closely monitored. Investigations on natural control factors and weather conditions (humidity and rainfall) affecting asparagus aphid populations and their management are in progress.

The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsements by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. All pesticide recommendations provided in this publication apply to pest control in North Carolina. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain information about product usage in your locale and examine a current product label before applying any chemical. The information presented on pest biology is based on conditions in North Carolina and may not be applicable to your locale. For further information, we recommend that you contact the Cooperative Extension Service office in your county.