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Aphids

Photo courtesy of University of Nebraska, Dept of Entomology

Description
Aphids may be green, black, brown, red, pink, or some other color depending on the sap color of the host plant. They are usually slow-moving insects with somewhat pear-shaped bodies ranging from 1 /16 to 1 /8 inch long. There may be various sizes of wingless aphids (nymphs and adults) in a dense colony on a stem, on the underside of the foliage, or on the flowers. Later in the season, some may have relatively large, transparent wings. The slender antennae are conspicuous, and near the rear end of the abdomen there are two tubes called cornicles.


Figure 1. Aphid Life Cycle Texas Extension
Aphids on Pittosporum
Figure 2. Aphids on Pittosporum
Life History
The life history of aphids is somewhat complicated and varies with the species. One of the less complicated life histories proceeds as follows: Overwintering eggs on branches and stems hatch in the spring to produce a wingless form known as the stem mother. The unfertilized stem mother gives birth to living young in great numbers. Several generations may occur in this fashion, but in due time some individuals will develop wings (alates) and migrate to another host. Here they may deposit eggs for the winter or, after a few generations, migrate back to the original host to lay eggs.
Damage
Aphids are sucking insects that feed by thrusting a long beak into the plant tissue. They withdraw great quantities of sap, some of which they execrete as "honeydew". The honeydew makes the plant sticky. When trees are heavily infested with aphids, sidewalks, lawn furniture, and automobiles may become wet with honeydew. A sooty mold often develops with the honeydew blackening stems and foliage. This fungus is not parasitic to the plant, but reduces the amount of photosynthetic area. Leaves of plants may be distorted by aphids feeding on the undersides. Succulent stems may wilt or growth may be arrested by colonies of aphids. On the other hand, damage caused by aphids feeding on the bark of trees or woody shrubs cannot be readily seen.
Aphids on Milkweed
Figure 3. Aphids on Milkweed
Green Peach Alphids on Mustard Leaf
Figure 4. Green Peach Aphids on Mustard Leaf
Nonchemical Control
Plants that are well established and vigorously growing usually can tolerate low to medium aphid population levels. Newly transplanted trees or stressed plants are more vulnerable to aphid damage and control should be considered. Aphid populations are usually controlled later in the season by natural enemies such as parasites, predators, and pathogens. In some cases, populations may crash literally overnite due to weather conditions.

Aphids or Plant lice are most commonly green; however some species are black, pink, or yellow. They are small (only 2 tenths inch) soft-bodied insects. Clusters of aphids are commonly found on peas. They damage plants by sucking the sap out of the stems, curling and yellowing the leaves. While feeding they can inject poisonous saliva or organisms which can cause diseases. The insect secretes a liquid called honeydew which can grow mold fungus.

The cabbage aphid, Brevicoryne brassicae, is a small green aphid that feeds mainly on the brassica vegetables (mustard, cabbage, brussels sprouts.

The green peach aphid, Myzus persicae, is a lighter colored insect which feeds on over 300 species of plants.

Organic Controls:

Spray with soapy water, such as Dr. Bonners Peppermint soap.

Pick off individual aphids by spraying with water or squashing between fingers.

Beneficial Insects:

Ladybugs, lacewings, and wasp parasites.

Aphids--least toxic way to control


Aphids are tiny, soft-bodied, plant-sucking insects. They can be just about any color. Most are "naked," without a hard exoskeleton, but some species have a soft cottony substance over their bodies. Some have wings and some do not.

About one-10th of an inch long, aphids have long hypodermic needle-like mouth parts, adapted to pierce and suck out plant juices. Most secrete honeydew, a sweet, sticky substance which is a food source for ants, bees and flies.

Some kinds of aphids may spread plant viruses from one host to another. Dripping honeydew also encourages sooty mold growth on many plants.
  • Use smart landscape design. Do not have aphid-attracting plants where aphids or their honeydew will do harm. For example, birches are notorious aphid-attractors. Don't plant birches near driveways or decks, or your vehicles and deck will be sticky with honeydew.
  • Keep plants healthy. Plants with adequate supplies of nutrients, water and light can fend off aphids more easily than sickly or stressed plants. Avoid over-fertilizing. Succulent new growth attracts aphids. The use of slow-release or organic fertilizers helps avoid an overdose of nutrients to the plants.
  • Remove aphids physically from the plants they feed on. A periodic strong spray of water with the garden hose can work wonders with aphids on rose shoots and buds, bean plants, young broccoli and cabbage shoots and other tender garden foliage. Prune off badly damaged foliage. Also, yellow sticky aphid traps, sold in garden stores, trap flying aphids in a non-toxic sticky substance. Quarantine aphid-infested house plants.
  • Introduce or encourage natural aphid predators. Avoid the use of broad spectrum pesticides which kill aphid predators such as ladybugs and green lacewings. Do not purchase adult ladybird beetles, as they tend to disperse on release. A better predator to purchase may be the green lacewing, available for sale as eggs or larvae.

The best strategy is to grow plants that attract and foster natural predators, she said. These include yarrow, wild buckwheat, white sweet clover, tansy, sweet fennel, sweet alyssum, spearmint, Queen Anne's lace, hairy vetch, flowering buckwheat, crimson clover, cowpeas, common knotweed and caraway.
"This means you have to spray the soap solution directly on the aphids to eliminate them," said Gredler. "Make sure to check the underside of leaves and other hard to see areas for aphids. And remember - the soap spray is only effective as an insecticide until it dries. For plants that are in the sun, test an inconspicuous part of the plant first to see whether it will cause leaf burning. Always follow label instructions."

Using insecticidal soap on aphids allows predator insects with harder bodies to survive and naturally control aphids. Commercial formulations of these soaps have been extensively tested on plants so they are safer than homemade solutions, she added.

Aphids can be removed by hand if the infestation isn't severe. Spraying plants with a stream of water from a hose also defeats aphids, or simply knock them to the ground by brushing off leaves and stems.

Insecticidal soaps are another control alternative.

"Before applying sprays, be aware that nature supplies some checks on aphid populations in the form of insect predators," McNeilan said. If ladybugs or lacewing flies are present in the home landscape they will feed on and eliminate some of the aphids.

Aphids Soap Spray

1 cup vegetable or white mineral oil
1 1/2 cup water
2 teaspoons dish soap or Murphy’s soap

Spray this homemade aphid control mixture on the aphids every few days until the aphids recede. This home remedy to get rid of aphids will suffocate the aphids. Make sure that plants that are treated with this solution are keptout of direct sunlight as the oil may magnify the sunlight and burn the plants.

Predators to control aphids

Aphid predators are a natural way to kill aphids. These include lacewings, ladybugs and aphid predator (which is an actual bug called that). Introduce these beneficial bus to your garden as a natural way to kill aphids. Planting mint, fennel, dill, yarrow, clover and dandelions will also attract these insects to your garden.

Grow plants for a homemade aphid control

Growing plants that are especially attractive to aphids can actually help with a serious aphid infestation. Plants like nasturtiums, asters, mums, cosmos, hollyhocks, larkspur, tuberous begonias, verbena, dahlias, and zinnias are very attractive to aphids and are especially good for organic control of aphids. Grow these plants away from the plants you wish to keep aphids off. They will act as a lure, keeping the aphids away from the plants you wish to keep aphid-free.

You can also try planting garlic or onion plants nearby teh infested plants. The smell of these plants drives the aphids away. You can plant garlic and onions in pots for mobile homemade aphid control.

Spray hose to get rid of aphids

If you find an aphid infestation, you can spray the plant with you garden hose to knock the aphids off. Spray the plant every day until the plant is aphid free.


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