The unforgettable aphid

There are over 4,000 species of aphids and they often travel by wind or as a stow away on other plants and animals.

By Malaika Ross.

A cluster of dark aphids on a green leaf.
Aphids. Photo by Tricia Hogbin.

While working with my Sustainable Agriculture team on our garden plot, we encountered small black insects, which clustered on the leaves of the garden’s citrus plant. With a little investigative work we learned our citrus tree was experiencing an aphid (Aphidoidea) infestation. Since no one in the group had encountered aphids outside of our weekly gardening sessions, we were hoping aphids would be benign, but we quickly learned aphids cause substantial damage to plants.

Aphids are very small insects with soft bodies, which live off the sap in plants found in the leaves. They are black, green, brown and pink or absent of color. There are over 4,000 species of aphids and they often travel by wind or as a stow away on other plants and animals. Some species even develop wings and fly to nearby plants for food. Aphids are very destructive and seem to thrive in temperate zones. Some species are asexual and this makes reproduction a snap — a scary reality for farmers and gardeners here in Hawaii.

Within the Hawaiian archipelago, various species of aphids are responsible for damaging large numbers of agricultural plants and native Hawaiian plants. In our team’s garden plot alone, we experienced three separate aphid infestations. Aphids are an invasive species, which impact the health of Hawaii’s ecosystems. Aphids also vector plant viruses, which have been known to affect banana and papaya crops.

Control

So how does one handle an aphid problem?

Well, to keep an aphid infestation under control, it is important to deal with these invasive insects right away. There are a few ways you can contend with aphids. Once an invasion is underway, you could turn the host plant into a sacrificial plant. Since aphids are very resilient, allowing them to have one of your plants in the short-term may be a good compromise.

It has been the experience of my team that once you attempt to remove aphids from one plant, they can quickly spread to a nearby crop. It may be wise to wait until you have harvested a valuable crop in the area near the infestation before you attempt complete eradication.

For a long-term solution, try introducing one of the aphid’s predators to your garden or farm. Parasitic wasps and ladybugs may be a good option and have been shown to be very effective. Anoth- er option is to spray a simple solution of one-tablespoon mild dishwashing liquid added to one cup of vegetable oil on the infested areas of the plant.

Here’s to preventing aphid infestations!

-From the May 2013 issue of the Agricultural Club Newsletter, College of Agriculture, Forestry and Natural Resource Management, University of Hawai‘i at Hilo.