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Pea Aphid
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Homoptera: Sternorhyncha Aphididae Parthenogenic females are produced rapidly in both winged and unwinged generations the latter allowing for rapid dispersal of the bugs. The overwintering forms can store eggs. The hormonal balance may inhibit winged forms from developing. The bug may weaken plants by feeding or spread disease from one plant to another. The russian wheat aphid has caused severe damage in the midwest plains states.
Stylets penetrate leaf tissue and suck cell sap producing honeydew from excess carbohydrates. Cornicles produce an alarm pheromone — not the honeydew. Aphids have extremely high reproductive potential via parthenogenesis. Ants protect corn root aphids for the honeydew production. The aphid eggs may be overwintered in the ant nest; new generation of aphids placed on corn roots. The ants prevent parasite complex from controlling aphids. Aphids vector wilts, mosaics, dwarf diseases, plant cankers, galls. The green peach aphid transmits at least 12 viruses that attack such crops as potatoes, crucifers, beans, grapes, cucurbits, celery, lettuce, tobacco, sugarbeets and spinach. Thorzban treatment of irrigation lines in orchards. 4000 spp described; 30 spp are pests. 3 genera life styles:
Aphids Mainly:
There are many species which attack vegetable crops; they are frequently called plant lice. Populations can build up very quickly particularly under warm moist conditions. They are often important as carriers of virus from diseased to healthy plants. Large populations can damage young plants or make lettuce unmarketable.
Aphids feed by sucking plant sap. Saliva injected while feeding may carry plant viruses or may be toxic to the host plant. Feeding by large numbers discolors foliage, curls leaves and damages developing buds. The plants may be covered by a sticky substance — honey dew — which is excreted by the aphids.
Aphids are small, soft-bodied, slow-moving insects. They are often found in large colonies on the undersurface of leaves. A colony consists of winged and wingless adults and various sizes of nymphs. Aphids may be black, yellow, or pink, but mostly are various shades of green.
Most aphids overwinter as eggs on woody plants. Depending on the species of aphid, the entire season may be spent on one plant species or they migrate to one or more alternate hosts. Nymphs from overwintered eggs develop into wingless females which give birth to living young. These develop into wingless females. In early summer, winged females develop and fly to new host plants. In the fall, males develop. Mated females lay winter eggs.
There are no trap devices available. Monitoring consists of walking through the field and looking for the black aphids on beans, grayish mealy aphids on cole crops, green peach aphids on most vegetable crops, green pea aphids on peas, and pinkish aphids on the inside of lettuce heads. Presence of aphids early in the growth of plants can cause severe yield reduction or even crop failure. Close to harvest, aphids may not affect yield but may present a contamination in a processing or fresh market crop.
Infestation early in a plants life must be controlled to avoid crop failure. Infestation close to harvest must be controlled to avoid a contamination (e.g. green beans). High volume spraying is required to cover all parts of the plants thoroughly. Name: Gilkeson,
Linda A. Title: Integrated Pest Management Coordinator Reference Text: Aphids Most gardeners are familiar with aphids — the tiny, numerous pear-shaped insects that suck plant sap. There are hundreds of species of aphids, of many different colors, but they all have long antennae and a characteristic pair of short tubes extending backwards like tailpipes from their abdomens. They are usually found in crowded colonies on undersides of leaves and on tender shoots and tips of branches. Aphids are common pests on roses, cabbage family plants, beans, celery, fruit and shade trees, ornamental shrubs and flowers. They suck plant sap, which distorts leaves and new growth and may weaken the plant. Some aphids spread plant viruses and most aphids secrete copious amounts of honeydew as they feed, which leaves a sticky coating on leaves and fruit (or your car!) below. Unsightly, but harmless, black sooty molds often grow on the honeydew. Although some, like the cabbage or maple aphids, attack only one kind of plant, others, like the green peach aphid thrive on many different plants. It is important to realize that the presence of aphids is not always a problem — some plants are damaged very little by aphid attacks. Aphids feeding on shrubs and trees in late summer can help harden off new growth before winter.
Aphids reproduce in two different ways: in the spring, overwintered eggs hatch into females that do not mate, but who give birth to live nymphs continuously (up to 10 or more per day) during the growing season. In the fall, these "stem-mothers" produce male and female aphids that mate and produce eggs that overwinter. When the colonies become too crowded some of them develop wings and migrate to new plants.
Aphids are difficult to control using sprays because any survivors quickly develop new colonies. Aphid populations also become resistant to insecticides used repeatedly. The best long-term control for aphids is enlisting the aid of their natural enemies. An aphid infestation that is ignored by the gardener almost always disappears thanks to the action of hundreds of native species of predatory bugs, beetles, flies, lacewings, midges and numerous tiny parasitic insects. You can attract this army of native beneficial insects to the garden by planting flowers and herbs among the vegetables; protect them by not using insecticides. If you want to speed the disappearance of an aphid infestation, choose from the following list:
As a last resort, spray with domestic garden products containing pyrethrins, which are extracted from pyrethrum daisies*, or rotenone (use wettable powder formulations). Although these botanical insecticides break down quickly in the environment, they are as toxic at the time of application as other, more persistent chemicals. Always wear protective clothing, rubber gloves and a tight-fitting dust mask to spray pyrethrins or rotenone. Never use these insecticides near ponds or waterways because they will poison fish. *Tanacetum (=Chrysanthemum) cinerariifolium or T. coccineum.
In Utah, aphids
have been studied for many years. All true aphids belong to the
homopteran family Aphididae, which includes one of the most numerous
types of insects infesting plants. Over 550 Virtually everything man grows is attacked by one or more species of aphids, commonly called plant lice. They come in all colors including white, black, gray, yellow, red, pink, green, blue, or brown often with at least 2 combined colors. Some are immaculate, spotted or patterned, other are covered with various shapes and sizes of bumps, from dermal glands some secrete waxy white threads to hide under, and all produce sugary droplets of waste material called honeydew. The cornicles located on the dorsal side of the posterior abdomen secrete a defensive fluid. The honeydew excreted from the anus consists mainly of excess sap ingested by the insects, to which are added excess sugars and other waste material. This secretion falls onto leaves, twigs and fruit and stimulates the growth of a black, sooty mold. The mold not only mars the appearance of plants but may restrict photosynthesis. Honeydew also attracts certain ants and flies. The ants herd the aphids like cows, often protecting them from predators and parasites. The honeydew is collected from the aphids and used as food by the ants.
The life cycle of many aphids species is rather unusual and complex. Most species spend the winter in the egg stage, and these eggs hatch in the spring into females that produce living young parthenogenetically. Several generations may be produced during the summer season by females giving birth to live females. These females soon mature and also give birth to living females. Large populations of aphids can build up in a very short period of time by this method of reproduction. The first few generations often consist of wingless forms, but eventually winged individuals may be produced, that often migrate from the overwintering host to a different plant where this rapid reproduction continues. Later in the season winged females of most species migrate back to the original host where both males and females are produced, mate and lay overwintering eggs. Many variations can occur to this generalized pattern of reproduction depending on the species and t he environment.
Aphids feed by sucking fluids from their host plants, which may be damaged in one or more ways. Excessive fluid removal may cause wilting; stunting; yellowed leaves; decreased fruit size, yield, and quality; premature leaf drop; and even death to the plant. Many aphids inject toxins into the plant during feeding. In addition to the above symptoms, the toxins cause various plant distortion, leaf curling, leaf "burns" (due to accumulations of photosynthesis products in the leaves caused by blocked vascular tissues), and localized tissue death. Some host plants produce various types of galls in response to aphid feeding. These galls may or may not interfere with plant growth and fruit production. There are many species of aphids that inject live virus into the plant and serve as vectors of various plant diseases. In most cases the disease causes far more damage than does the aphid feeding. As aphids feed they extract nutrients from the plant fluids and excrete large quantities of water and dissolved sugars. This liquid material serves as a substrate for various saprophytic molds that may reduce the quality of the fruit, discolor and reduce photosynthesis in the leaves of plants. The excreted honeydew often drops from the trees onto cars, lawn furniture, sidewalks and other objects to create a sticky mess underneath the tree.
There are numerous non-insecticidal control strategies that may
be used to decrease aphid damage. They would be much more destructive
to vegetation were it not for their numerous parasites and
Migrating aphids may be attracted and captured in yellow pans of water (add a few drops of detergent to make the aphids sink) or yellow sticky traps. Conversely, they can be repelled from host plants by planting through holes in strips of aluminum foil or by placing strips of foil around plants or between the rows. These techniques are somearial useful during aphid migrations, but they are not particularly effective in reducing the overall problem. Regardless of the product used, read and follow all label directions. Check the label to make sure the material is registered for use on the plant or crop you wish to apply it on. Apply the material at the appropriate rate, at the proper time and use the recommended application techniques for all insecticides recommended in this fact sheet. The pesticide user is always responsible for the effects of pesticide residues on his plants as well as problems caused by drift from his property to other properties or plants. From: WVNGSSN@clust1.clemson.edu (WILANT VAN GIESSEN)
Dr. Debbie
Henderson, E.S. Cropconsult, Ltd. Vancouver, BC. Approximately 400 households were involved in a project initiated by the City of Vancouver in response to complaints about honeydew. Honeydew is a sticky substance excreted by aphids as they feed on plant sap. It leaves a sticky residue on sidewalks and cars parked beneath city trees. The objective of the project was to determine if there was a non-toxic or biological way to control aphids and thereby reduce property damage from honeydew. The city wanted to find alternatives to chemical controls that did not involve removing aphid affected trees. Two methods were tested in 1994:
The sticky bands were tested because they stop ants from climbing the tree trunks. Ants collect the sweet honeydew and protect aphids by removing predators from the aphid colony. It was hoped that controlling the ants would allow natural enemies to control the aphids. Plastic clipboards were laid on the ground under the trees to collect honeydew dropping from trees. Each week during the summer, the amount of honeydew was monitored. Trees were also periodically sampled for aphids. Neighbourhood residents assisted by preventing passersby from vandalizing the tree bands or removing clipboards. Early results showed that aphid numbers and honeydew quantity appeared to be lower in the areas where the Aphidoletes were released. The sticky bands seemed to have little or no effect. Insects other than aphids (such as scale insects) may have been contributing to the honeydew deposit. More work is needed to assess this method of controlling aphids and a similar project will continue in 1995 through the city of Vancouver. Cooperators on the project were: E.S. Cropconsult, Ltd., Applied Bio-Nomics, Ltd., The city of Vancouver and the federal Pest Management Alternatives Office. see also:
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