Aphids on Landscape Plants
Aphids or “plant lice” may infest almost any plant. They are more commonly found on camellia, crape-myrtle, gardenia, hibiscus, ixora, oleander, palm, rose, as well as nearly all annual plants. Aphids have piercing-sucking mouthparts and cause damage by sucking the plant juices. However, their ability to transmit plant viruses may be more harmful than any direct feeding damage.
Aphids are soft bodied pear-shaped insects generally less than 1/8 inch long and usually green in color but many are black, brown, pink, yellow, blue, or white. Most aphids are wingless but when colonies become overcrowded or the host plant becomes undesirable, winged forms are produced which establish new colonies. Aphids have two short cornicles or tubes at the end of their bodies. These insects are commonly found on the stems or undersides of young leaves in small colonies.
Some examples of aphid predators are lady beetles, praying mantids, assassin bugs, ambush bugs, and aphid lions. Spiders also prey on numerous insect pests. Aphids that have a small hole in a bloated-looking body were parasitized by tiny wasps. If predators are present or the pests show signs of parasitism, every effort should be made to preserve the beneficial insects. Delay applying a pesticide until damage appears, and provide the beneficials an opportunity to control the pest populations.
Healthy (yellow) and parasitized (brown/swollen) oleander aphids.
Examine your plants weekly during the spring, summer, and fall. Look at the undersides of a few leaves on each plant and observe the stems for aphids, especially the new growth. The use of a 10 to 15 power hand lens or magnifying glass aids in detection and identification. Learn to determine when aphids are present in damaging numbers and to evaluate the potential of the predator or parasite population. To aid in locating aphids, a sheet of white paper or cloth may be held beneath the leaves and the foliage struck sharply. The insects will fall onto the paper and can be more easily observed and identified than on the green foliage.