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Mon, June 17

Aphids are a pain, but infestations can be handled

SANJAY ACHARYA/Courtesy<br /><br /><!-- 1upcrlf2 -->Aphids are common garden invaders around the world, but there are many options when it comes to eliminating them or at least getting their population down.

SANJAY ACHARYA/Courtesy<br /><br /><!-- 1upcrlf2 -->Aphids are common garden invaders around the world, but there are many options when it comes to eliminating them or at least getting their population down.

KINGMAN - There are some bugs that are ugly and destructive and can be picked off and squashed or drown. There are others that are just plain a nuisance and simply nasty little critters. Aphids, in my opinion, are nasty little critters and a complete nuisance.

Aphids are the most common garden and landscape pest throughout the world, occurring in almost any plant zone. Summer, winter, spring and fall, as soon as you think you have them licked and under control, there they are again.

Aphids are soft-bodied, pear-shaped pests with long legs, long slender mouth parts and antenna. They are slow-moving and vary in length from 1/16 to 1/4 inch. Aphids can be almost any color, but green, black, red, white and gray are the most common.

Some are covered with a white threadlike material, which makes them appear woolly, while others may be covered with a fine dust. There are winged and wingless individuals of most species.

Aphids can be identified by a beak or rostrum that sits far back on the underside of the head. Their antennas are rather long and placed in the front of the head between the eyes. The feet are two-jointed and terminate in the claws. Many aphids have a pair of tubelike structures called cornicles projecting out of the hind end of their bodies through which they emit a sticky, protective substance commonly referred to as "honeydew."

Aphids live in large colonies and reproduce rapidly. Most aphids in mild climates reproduce asexually throughout most or all of the year, with adult females giving birth to live offspring (often as many as 12 per day) without mating.

The young aphids mature in 10 days and are called nymphs. They molt, shedding their skins about four times before becoming adults. There is no pupal stage.

Some species mate and produce eggs in fall or winter, which provides them a more hardy stage to survive harsh weather. In some cases, these eggs are laid on an alternative host, usually a perennial plant, or over winter in bark or ground litter for winter survival.

Life cycles vary by species but, generally, only female aphids are present during the summer. This wingless form of aphid is known as the stem mother. After one or two generations, winged forms are born and fly off to other plants.

Males are produced in the fall, at which time mating occurs. When the weather is warm, many species of aphids can develop from newborn nymphs to reproducing adults in seven to eight days.

On the average, an aphid lives for about one month and each female produces 80-100 offspring.

An aphid feeds on its host plant by sucking plant sap through a beaklike feeding tube inserted into plant tissue, thereby weakening stems and leaves.

Low to moderate numbers of leaf-feeding aphids are usually not damaging in gardens and trees. However, large populations cause curling, yellowing and distorted leaves and stunting of shoots; they can also produce large quantities of the so-called "honeydew," which sometimes turns black from the growth of a sooty mold fungus.

The honeydew attracts ants, flies, wasps and other insects. Some aphid species inject a toxin into plants, which further distorts growth.

A few species cause gall formations. Aphids may transmit viruses from plant to plant on certain vegetables and ornamental plants. Squashes, cucumbers, pumpkins, melons, beans, potatoes, lettuces, beets, chards and bok choy are crops that often have aphid-transmitted viruses associated with them.

These viruses cause mottling, yellowing or curling of leaves and stunting of plant growth.

Check your plants at least twice a week for aphids when plants are growing rapidly. Many species of aphids cause the greatest damage when temperatures are warm but not hot (65 to 80 degrees).

Catch infestations early. Once aphid numbers are high and they have begun to distort and curl leaves, it is often hard to control them because the curled leaves shelter aphids from insecticides or natural enemies.

On trees, clip off a few leaves from several areas to check for aphids. Also check for evidence of natural enemies such as lady beetles, lacewings, Syrphid fly larvae and mummified skins of parasitized aphids.

Ants are often associated with aphid populations, especially on trees and shrubs, and often are a tipoff that an aphid infestation is present.

High levels of nitrogen fertilizer favor aphid reproduction. Never use more nitrogen than necessary. Use less soluble forms of nitrogen and apply it in small portions throughout the growing season rather than all at once.

Because many vegetables are primarily susceptible to serious aphid damage during seedling stage, losses can be reduced by growing seedlings under protective covers in the garden or in a greenhouse. Protective covers will also prevent transmission of aphid-borne viruses.

Another way to reduce aphid populations on sturdy plants is to knock them off with a strong spray of water. Most dislodged aphids will not be able to return to the plant, and their honeydew will be washed off as well.

Insecticidal soap, neem oil and narrow-range oil (e.g. supreme or superior paraffinic type oil) provide temporary control if applied thoroughly to cover infested foliage.

To get thorough coverage, spray materials with a high volume of water and target the underside of the leaves as well as the surface.

These soaps and oils only kill aphids present on the day they are sprayed.

Do not use soap or oils on water-stressed plants or when the temperature is over 90 degrees.

Supreme or superior-type oils will kill overwintering eggs of aphids on fruit trees if applied as a delayed dormant application just as eggs are beginning to hatch in early spring.

These treatments will not give complete control of aphids and are probably not justified for aphid control alone. Earlier applications will not control aphids.

Many other insecticides are available to control aphids. They're for use on nonfood crops, including foliar application of Malathion, Permethrin and Acephate.

While these materials may kill higher numbers of aphids than soap and oils, their use should be limited because they also kill the natural enemies that provide long-term control of aphids and other pests. Repeated use of these materials may also result in the development of resistance to the material by the aphid.

The Farmer's Almanac listed the following suggestions for aphid control:

• Stir together one quart of water, one teaspoon of liquid dish soap and a pinch of cayenne pepper. Spray on plants, top and bottom of the leaves.

• Organic controls include alcohol spray (isopropyl alcohol, straight or diluted), soapy emulsion (can be mixed with alcohol) horticultural oil (read the directions) and pyrethrum spray.

• In a spray bottle, combine two parts rubbing alcohol, five parts water and a teaspoon of liquid dish soap. Spray leaves both top and bottom.

Fortunately, aphids have many natural enemies that are very effective.

Chief among these are lady beetles (lady bugs), with both adults and larvae dining on them. Other major predators include lacewings, small parasitic wasps, Syrphid flies (aka Hover flies) and soldier bugs.

When considering pesticides for aphid control, remember that moderate populations of many aphids attacking leaves will not cause long term damage.

Low populations can be tolerated in most situations and aphids will often disappear when natural enemies arrive.


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