Artichoke Aphid

Artichoke aphids are pale greenish-white to yellowish-green, almost translucent aphids with pale appendages. The tips of the very long cornicles (siphunculi) are distinctly dusky in color. The tubercles (located at the base of the antennae) are diverging in contrast to those in the green peach aphid, which are converging. Wingless adults have a long capitate hair on the third and the posterior abdominal segments; winged adults have an almost rectangular solid black spot on their abdomen. This aphid overwinters on its primary hosts, Elaeagnus species (Russian olive, silverberry, and others), migrating in summer to thistles (Circium, Carduus) and to artichokes where it can cause economic damage.

Large numbers of these aphids cause artichoke leaves to curl and turn yellow and the plants to show retarded growth, resulting in the formation of undersized or deformed artichoke buds. In addition, bud stalks weaken and can no longer support the weight of developing buds, causing them to droop. Also, buds that are close to harvest get contaminated with aphid bodies. Besides this direct-feeding damage, artichoke aphid characteristically secretes copious amount of honeydew, which is deposited onto leaves and developing artichoke buds in the lower canopy, giving them a wet and shiny appearance. Honeydew deposits on the foliage result in the growth of sooty mold, which covers the leaf surface and interferes with photosynthesis. It is estimated that 10 to 15% of the crop harvested from August to September is lost because of poor quality that is a result of aphid damage. Also, aphid injury may delay the fall harvest by several weeks because of retarded plant growth.

Artichoke aphid is a serious problem on perennial artichokes during summer, when the average humidity and air temperature are in the high range. It is not a problem in southern California annual artichoke fields. When choosing insecticide treatments to control other pests, consider the impact of the materials on natural enemies of this aphid. When conditions are ideal for development of populations, monitor the crop weekly to determine the need to treat.

Several parasitic wasps attack aphids in artichoke, most notably species in the genera Diaeretiella and Lysiphlebus. General predators including lady beetles, syrphid fly, 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.

Destroy crop residue immediately after harvest.

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

An outbreak of artichoke aphids is most likely to occur during periods of high average daily temperatures coupled with high relative humidity (98–100%). These conditions generally prevail from June to September. Intensify field monitoring during this period by making weekly observations. This aphid remains on the underside of the older leaves when population levels are low; at higher population levels, aphids spread rapidly throughout the plant. A population density of an average of 3 aphids per leaflet is considered a treatment threshold. At this population level, isolated plants will start to show the sooty mold on the foliage. Within a few days, the infestation becomes more conspicuous as large contiguous areas start turning black from the growth of sooty mold.