APHIDS


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MEET THE PEST

Aphids are pests of vegetables, field crops, shrubs, flowers and ornamental trees. They like to feed on cabbage, peas, potato, tomato, beans, roses, ornamental flowers, trees and shrubs (birch, elm, ash, maple, oak and pine). Healthy plants can tolerate a small number of aphids, however, damage results when large numbers are present. The aphid uses its needle-like mouth piece to suck sugar-rich sap from the plant.

Aphids are small (less than 1/10 inch or 2 3/5 mm long), have long antennae, and are most commonly green in colour but can be yellow, pink, red, grey, black or brown. A short pair of tubes which are located on the abdomen are used for defensive purposes as they produce a spray warning when the aphid is threatened. Most aphids are wingless. However, when the temperature is not suitable or over-crowding takes place, some species can form wings and move to new areas.

When a plant is attacked by a large population of aphids, damage such as reduced growth, wilted leaves, drying branches, stunted needles, curled, yellowed or downward cupped foliage may result. Many aphids remove excess sap from plants and excrete it. This clear, sticky, sweet substance, called honeydew is found below the host plant and may act as an attractant for other insect pests such as ants. The excess honeydew also acts as a host for a harmless black sooty mold which often grows in the secretion. Some species of aphids are also known to transmit viruses to the host plant upon which it feeds.

LIFE CYCLE

The aphid has three stages: egg, nymph and adult. Aphid populations can reach high numbers very quickly. This is possible because they have a high reproductive rate, some females can give birth to nymphs without mating and a large percentage of the offspring are females.

Eggs overwinter on the host plant and a generation of females hatch in the spring. Within ten days of being born, the female can give birth asexually (without mating) to a second generation of females. This process can continue until the fall, when winged males are produced to mate with remaining females. The eggs which are produced from this union overwinter. The following spring, the cycle continues.

CONTROL

Biological

There are several natural enemies which feed on aphids. Included in this list are ladybugs, lacewings, assassin bugs, syrphid fly larvae, adult wasps, spiders and chickadees. Of this list, ladybugs consume the largest number of aphids. Parasitic wasps are also very effective in aphid control. The parasitic wasp deposits an egg inside the body of the aphid. The egg hatches into a larva that consumes the aphid, leaving only an empty shell. Biological control can only be effective if natural enemies are present. Thus, it is important to attract and protect them. Tansy and marigold plants can be used to attract beneficial insects.

Additional ladybugs can be purchased to increase populations. Check with your local garden center representative for ordering and availability.

Physical

There are several physical control methods to use in controlling aphid populations. One such method is to spray a steady stream of water at the host plant to knock aphids off. Once on the ground, the fallen aphids will be available to ground predators and this will also make their return to the host difficult. Prune affected areas of trees to remove aphids and overwintering aphid eggs. Rub or hand pick aphids from affected plants to reduce populations.

Aphids are attracted to the colour yellow. Try controlling aphids by using yellow sticky traps which can be bought or made. To make a sticky trap, spread petroleum jelly over a yellow index card and place in the area where aphids have been observed. Another option is to fill yellow pan traps with soapy water and place the trap close to the host plant. The aphids will be attracted to the trap. The soap breaks the surface tension of the water causing the aphid to sink and drown.

Another physical control measure involves using aluminum foil sheets as mulch. Place the aluminium at the base of low plants. The reflection confuses the winged aphids, making landing difficult.

If a plant is heavily infested, it may be necessary to destroy it. This will cut down on overwintering sites and reduce future populations. Another option is to place row covers over plants because they serve as a barrier to aphids while allowing light, water and air to reach the plant.

Chemical

If biological and physical control measures are not effective, use a pesticide which will have a minimal impact on both you and the environment. Insecticidal soap can be sprayed on infested areas of plants to control aphid populations. Pyrethrum can also be sprayed on infected plants. During the fall, applying dormant oil helps to kill overwintering eggs.

If the above measures are not effective, consult with an expert at a garden center for additional pesticides available. Before using pesticides, consult the Backyard Bug Brigade Brochure which contains information on safe pest control.

Always use a registered domestic class pest control product labelled for aphid control and carefully follow the label directions.


[ First Page | Aphids | Biting Flies (Mosquito & Black Fly) | Carpenter Ants | Chinch Bugs | Cockroaches | Cutworms | Earwigs | Eastern Tent Caterpillars | European Marsh Crane Flies | Fleas | Mice & Rats | Silverfish | Wasps (Yellow Jacket) | Turf Weeds | White Grubs | Pesticide Regulations ]