Description of the Pest

Several species of aphids may be found on artichoke plants. These aphid species vary in color (from light green to black), size, and shape. All are soft-bodied insects. The most important aphid pest is the artichoke aphid, which is covered separately. Other aphids that may occur include green peach aphid, black bean aphid, and pea aphid. They form dense colonies on the undersides of artichoke leaflets, and in some cases on the artichoke petioles. Winged aphids form under specific conditions of overcrowding or plant stress and disperse to other plants or fields.

The green peach aphid occurs sporadically throughout the year. Populations start on lower leaves. In heavy infestations, they may be found throughout the plant. On the central coast, populations peak in spring and fall and decline in summer and winter. Spring populations generally build up on weed hosts occurring in the field and in uncultivated areas around the fields and move to artichokes during March and April. In the southern coastal areas, populations generally peak in September to November and again in March to April. In the southern desert area, where artichokes are planted as an annual crop in August, green peach aphids attain peak densities in January and February, when the crop is ready for harvest.

Occasionally pea aphid and black bean aphid infest artichokes that are located close to other row crops.

Damage

Unlike artichoke aphid, green peach aphid does not lower yields or turn leaves yellow. Damage is more cosmetic in nature when green peach aphid moves into artichoke buds, contaminating the outer bracts. At low to moderate infestation levels, these aphids can be removed by washing the produce with water before packing. However, as the growers move towards field packing, these low infestations may become more economically significant.

Occasionally black bean aphid populations move into developing floral heads, which can require the heads to be culled. Also, the aphids produce honeydew, upon which black sooty mold grows and contaminates the artichokes.

Management

Normally these aphids do not warrant control unless contamination is a concern.

Biological Control

Several parasitic wasps attack aphids in artichoke, most notably species in the genera Diaeretiella and Lysiphlebus. General predators including lady beetles, syrphids, and lacewings also consume aphids. In addition, a portion of the population may be killed by a fungal disease caused by Entomophthora aphidis. However, naturally occurring predators, parasites, and pathogenic fungi rarely provide timely control because of considerable time lag between the buildup of the parasite or predator populations and the aphid populations. Preserve populations of beneficial insects by avoiding unnecessary insecticide applications and by providing acceptable habitat for these predators and parasites.

On artichokes grown in isolated small areas in the southern deserts where insecticide use is minimum (0–3 applications per year), growers have released convergent lady beetles for aphid control with some success.

Cultural Control

Destroy crop residue immediately after harvest. Avoid other aphid-favored crops, such as lettuce, in adjacent upwind fields.

Organically Acceptable Methods

Biological controls, cultural controls, and sprays of neem oil are acceptable for use on organically certified crops.

Monitoring and Management Decisions

Outbreaks of green peach aphid are more likely to occur during summer and fall. Intensify field monitoring for aphids when adjacent fields with aphid-favored crops are harvested. Inspect the bottom side of leaves and behind lower bracts of developing artichoke buds for aphids on a weekly basis. Treat if significant populations of aphids are present on artichoke buds. Aphids may be a problem in only one part of a field. Check the entire field carefully to see if spot treatments of small portions of fields may be sufficient to control the aphid problem.

Black bean aphid is usually not abundant enough to warrant treatment. If heavy populations occur in leaves, treat before they move into the floral buds.

Pesticides and Natural Enemy Releases