Fact Sheet – IP2

Aphids on Ornamental Trees and Shrubs

1100 W. Moana Ln., Reno, NV 89509 11301 So. Virginia St., Reno, NV 89511

Key Points:

· Aphids occur on almost all types of ornamental trees and shrubs.

· Aphids can produce a new generation every 7-10 days.

· Damage is usually slight except when populations are high and leaf curl can occur on peach, ash, plum, honeysuckle, and snowball viburnum. Some aphids can cause galls.

· Aphids can be found in a wide range of colors from orange, red, green, yellow, brown, and black.

· Controls can be effective using natural predators, systemic insecticides (when leaves are curled tightly) and contact materials such as oils, soaps, Neem and insecticides.

Identification

Aphids are soft-bodied insects with long slender mouth parts adapted for piercing stems, leaves and other soft plant tissues. Almost every plant has one or two species of aphid that will attack it. Proper identification is not necessary to control them. Aphids will be found in green, yellow, black, grey, or red tones depending on the plant species they attack. Some aphids produce a secretion of a waxy or wooly material over their bodies. All are pear shaped with long legs and antennae. Most will have a pair of tube-like structures projecting backward out of the abdomen. No other insect has these structures. Most aphids will be wingless, though a fair number of species do bear wings in the spring and fall.

Most aphids will excrete large quantities of honeydew which is a sticky, sweet substance. At times excessive honeydew can be a nuisance dripping from trees on the car, patio, or walks. A sooty mold or fungus can grow from this honeydew which creates an unattractive gray to black covering on the foliage or trunk. Ants are attracted to this sweet honeydew and will feed on it. Ants will also move aphids from plant to plant and protect them from natural enemies.

Life Cycle

Aphids have many generations in a single year. In milder climates they can reproduce asexually with adult females giving birth to live offspring often as many as 10-12 per day. The young aphids as nymphs look exactly like the adults and shed their skin about four times as they grow into adults. During warm weather aphids can develop from newborn nymphs to reproducing adults in 7-8 days and each adult can produce up to 80 offspring in a week, thus aphid populations can increase very quickly. Eggs are laid on a perennial host to overwinter.

Damage

When populations are low to moderate, the damage is usually slight, especially on larger plants and trees. When populations reach a high level, curling, yellowing, leaf distortion, and stunting may occur. Some species may inject a toxin into plants which can cause distortion or gall formations. The biggest concerns are viral exposure to landscape plants, honeydew formation, and the resultant sooty mold.

Management

The damage caused seldom leads to plant death; however, it can warrant the need for control. Several methods of control can be used. To avoid destroying beneficial insects non-chemical methods should be considered first.

The first step is to carefully monitor your plants at least twice a week for aphids as well as the presence of beneficial insects such as ladybugs. Catch infestations; once populations are high and distortion and curling have begun, control is much more difficult. Check the underside of leaves. Ants are often associated with aphids and can be an indication of populations building up. Watch for signs of natural enemies such as lacewings, syrphid flies and ladybugs. Plant disease and dead aphids can be present as well.

The next control would be biological (introduction of insects that feed on aphids). Besides the natural buildup or our placement of beneficial insects, some cultural controls can be used. Simple use of high pressure water from a hose, removal of aphid attracting weeds such as sow thistle and mustards, inspection of newly purchased plants, pruning of heavily infested branches, and the use of Tanglefoot® to deter ants are all effective ways of controlling aphids.

Several levels of chemical controls are available with some sprays considered biological. Insecticidal soaps, Neem oil, and horticultural oils (especially Ultra Fine Oil) are temporary controls. It is critical that the underside of leaves be sprayed when applying any spray. These are contact sprays which means aphids not physically exposed will repopulate the plant. Aphid problems originating from eggs that overwinter are best controlled with dormant oils. Do not use oils or soaps in temperatures over 90º F.

For most aphid problems, especially those associated with leaf curls, insecticides that move systemically within the plant provide the best control. These materials also won’t affect the natural enemies. The most common material in granular form is Disyston, often used in combination with plant food and worked into the soil and picked up by the roots. DO NOT USE systemics on food crops. Another systemic material new to the market is Merit which is effective on all sucking insects except spider mites. As with any chemical, read the label and then follow it. Contact insecticides are useful for aphid control when insects are exposed on the plants. A contact insecticide such as Malathion is good to use as a spray. Sevin does not control aphids very well except woolly aphid on evergreens. Diazinon and Dursban are no longer available for home use.

Remember that moderate populations of any insect, not only aphids, do not cause long term damage to ornamental trees and shrubs. Monitor your plants and determine when you need to step in or let Mother Nature handle it. Don’t let a few chewed up leaves be of concern.

1100 W. Moana Ln.

Reno, NV 89509

775-825-0600

www.moananursery.com

11301 S. Virginia

Reno, NV 89511

775-853-1319