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Aphids RSS feed


written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- MAY 30, 2014


‘Help! My plant has curled leaves. What’s wrong?’ This is a question that I often get asked, but there is not an easy answer. Curled or distorted leaves can be caused by more than one thing. Aphids, weed killers and plant viruses all cause malformed leaves on plants.

You might think that aphids would be the easiest of these to diagnose. All you have to do is look for these little plant suckers inside the curled leaves. Aphids are pear-shaped soft-bodied insects that are fairly small, ranging in size from less than 1/16 inch to more than 1/8 of an inch long.

Aphids can be green, yellow, gray, pink-purple, or even black aphids. Typically, aphids are found in groups on tender new growth and buds. Their numbers can build up quickly because early in the season all the aphids are females that give birth to live females that produce more females and so forth.

Aphids feed on plants by sucking out plant sap with piercing, sucking mouth, sort of like a straw in a juice box. When aphid numbers are small, they don’t do much damage to plants, but large populations can stunt plant growth. Some aphids also inject a toxic saliva into the plant that causes distorted growth. These curled leaves then provide the aphids with protection from some predators and pesticide sprays.

Two aphids that often cause severe leaf curl in area gardens are the green peach aphid and the wooly ash aphid. However, when gardeners uncurl malformed leaves to look for these aphids, they may not find them. That is because the aphids have departed their early spring hosts and moved to summer hosts before they return in the fall. The green peach aphid which attacks plums, peaches, and nectarines in early spring spends the summer on weeds and vegetable crops.

The wooly ash aphid has a body covered with waxy secretions that makes it look ‘wooly.’ These aphids feed on new growth of ash trees in the spring and then spend the summer on the roots of the trees. They move back to the top of the trees to mate in fall.

In the past, when gardeners encountered clusters of aphids on their plants they would rely on chemicals to help manage the problem. Today, gardeners are encouraged to try non-chemical approaches first before using pesticides.

– Avoid applying high levels of nitrogen fertilizer which promote excessive vegetative or lush soft growth that favors aphid feeding.

– Knock aphids off a plant using a forceful stream of water, taking care not to the plant. The aphids will not climb back onto the plant.

– Learn to recognize and encourage natural predators and parasites that feast on aphids.

– Control ants feeding on the honeydew (sugary plant sap) secreted by the aphids. They actually protect aphids from predators.

If you do decide to use a pesticide spray, avoid broad spectrum insecticides that will also kill aphid predators. Insecticidal soaps and horticultural oils will effectively control aphids present and visible on plant shoots and leaves. These are contact insecticides and must come in direct contact with the aphid bodies to be effective. Because many aphids feed on the bottom sides of leaves, be sure to get good coverage when using these materials. Most aphids that feed on woody plants early in the season, such as the green peach aphid and the wooly ash aphid, are best controlled with delayed-dormant sprays in late winter just as the buds start to open.

Published: 5/30/2014 11:53 AM


written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA

What’s bugging you? Our mild winter and extraordinary cool weather this spring has allowed some garden insect pests to thrive. One group of these pests is what I call ‘nasty little suckers’ or aphids.

The thing that makes aphids so insidious is that most are ready and waiting to attack as soon as new growth starts to emerge in the spring, plus they have an extraordinary capacity to multiply quickly. A wingless adult female aphid is capable of producing 50 to 100 all female babies without needing to mate or lay eggs first.

These baby girl aphids quickly mature into adult females and start producing their own babies in about a week with each of those producing babies… and it goes on and on. It’s not hard to believe that just one overwintering aphid can translate into thousands within weeks. If gardeners aren’t vigilant, a small population of aphids can quickly get out of control.

Identifying aphids isn’t as easy as you might think, since they do vary in appearance. Many gardeners are familiar with green aphids and are surprised to find that there are also black, pink, yellow, blue-gray, and whitish aphids. Aphids have pear-shaped soft bodies and are usually less than 1/8 inch in length. Most aphids don’t have wings unless their population becomes crowded and they need to find a new feeding site.

Aphids have piercing-sucking mouthparts that allow them to tap into and suck out plant sap. They often excrete a sugary liquid called honeydew, leaving sticky, shiny spots on lower leaves and objects beneath, such as cars beneath aphid infested trees. When checking for aphids examine the stems and leaf undersides of new growth,. Aphids don’t scurry away like many other insects, they just keep sucking away.

Besides the bother of honeydew, aphid feeding can injure plants if an infestation is severe. As a result of heavy aphid feeding leaves may turn yellow. Many aphids also inject their saliva into the plant causing curling, stunting, puckering, and distortion of new growth. Aphids also damage some plants by transmitting viruses via their feeding.

What can you do about an aphid problem?

1. A forceful spray of water will knock aphids off a plant and those knocked off will not go back to the plant. Doing this periodically can keep modest populations under control.

2. Work with nature by encouraging natural predators like ladybugs and their larvae and not using pesticides harmful to beneficial insects.

3. Aphids are fairly easy to kill, but many softer or organic insecticides such as insecticidal soap only work when they directly contact the aphids’ bodies. When using these materials its important to apply them where the aphids are located, often on the undersides of the leaves. If aphid feeding has already caused leaf distortion, the aphids stay protected inside the curled leaves and these materials are not very effective.

4. There are systemic insecticides available, applied as sprays to the leaves or as drenches to the roots, that get into the plant sap and kill the aphids when they feed. This is the only way to kill aphids protected by curled leaves. However, most of these products are only labeled for use on ornamental plants, not fruits or vegetables.

5. If the aphids are on a woody plant, consider applying a delayed dormant oil spray early in the spring just before the buds open. This can kill overwintering aphids before they get a chance to start feeding or multiplying.


Shhh! It’s the Secret Garden Tour. Next weekend is your opportunity to take a self-guided tour to see some of the prettiest and unique gardens in the area. The Academy of Children’s Theater (ACT) Secret Garden Tour is holding their 15th annual garden tour that will take you to six beautiful local gardens, each with a special title reflecting its theme. New this year, will be performances or demonstrations by a variety of local musicians and artists at each garden. The tour runs from 11:00 a.m. to 4:00 p.m. on Saturday, June 29th and Sunday, June 30th. You can purchase tickets for $15 at ACT (213 Wellsian Way in Richland), Heritage Nursery, Wood’s Nursery, or on-line at The funds raised by the tour support ACT’s programs and classes.

Published: 6/21/2013 2:55 PM


written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA

Last week we talked about when and how to prune roses. Since spring is right around the corner, now’s a good time to talk about the two rose problems that local gardeners often face… aphids and powdery mildew.

APHIDS: Aphids are small green or pinkish soft-bodied insects found in clusters on succulent new bud and stem growth. The aphids suck sap from the plant. When they’re present in high numbers, they damage growth. Rose aphids overwinter as eggs on buds and stems, emerging at the same time that new growth begins in the spring.

Horticultural oils can be used to help minimize aphids problems by smothering aphids eggs before the young aphids emerge. The oils are applied at the delayed dormant stage, when the buds start to emerge.

There are other least-toxic ways to discourage the buildup of aphid infestations on roses. Avoid excessive or unnecessary applications of nitrogen fertilizer. The nitrogen promotes vigorous, succulent growth where aphids like to feed. Using a slow-release or low nitrogen fertilizer can avoid lush early-season growth.

Another non-chemical option for managing aphids is water. A strong stream of water can be used to wash aphids off rose leaves and stems. Spraying roses regularly with water is an easy way to keep aphid populations down.

If these methods fail, there are a number of organic and inorganic pesticides for aphid control. The easiest to use are the systemic insecticide products that are mixed with water and applied to the soil for uptake by the roots. The Bayer Advanced product line includes several soil-drench products containing imidacloprid for use on roses.

POWDERY MILDEW: Powdery mildew is a fungus disease characterized by a white powdery coating on leaves and buds. You can minimize powdery problems by not encouraging succulent growth which is most vulnerable to infection by powdery mildew. Also, sprinkling plant leaves with water helps by washing spores off the plant.

One new ‘organic’ spray that gardeners have been reading about for control of powdery mildew is milk, yes the stuff that comes from a cow. However, while this recommendation has appeared in various gardening publications, Linda Chalker-Scott, WSU Extension Horticulturist, points out that there have been no published scientific studies investigating the use of milk to prevent powdery mildew on roses or other ornamental plants. There have been studies on the effectiveness of milk spray applications for the control of powdery mildew on melons, cucumbers, and squash. These studies indicate that whole milk does provide some control of powdery mildew.

Chalker-Scott notes that the only anecdotal evidence, not scientific research, indicates that milk is effective in controlling powdery mildew on roses. She also points out the drawbacks of using milk for powdery mildew prevention include the unpleasant odor of the milk fat as it breaks down, the growth of benign fungal organisms that colonize the leaves as part of the break down process, and that milk may only be effective if it’s applied prior to powdery mildew developing.

With those drawbacks, you may prefer to use an organic or inorganic fungicide for control of powdery mildew on roses Most of these require frequent (every seven to ten days) application to protect new growth as it develops. However, tebuconazol can be applied as a soil-drench for uptake by the roots. Several Bayer Advanced rose care products contain both tebuconazol and imidacloprid, providing aphid and powdery mildew control for ‘up to six’ weeks. These products are a bit pricey, but they avoid the risk of spray drift and don’t require spray equipment or frequent re-application.
Published: 3/9/2012 11:33 AM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Last week a frustrated gardener came in and said that the spinosad pesticide product that he had purchased wasn’t doing anything to control the aphids on his roses. I wasn’t surprised. Spinosad is most effective in controlling chewing insects, such as caterpillars, leaf beetles, leaf rollers, and thrips. Aphids are a sucking insect. There are other materials that are much more effective against aphids.

While it’s sometimes hard to find knowledgeable staff at stores that sell pesticides, the pesticide label is a great source of information. It will tell you what types of plants you can use the product on, how to apply the material, and what type of pests it will control. This gardener’s spinosad container was empty so he gave us the label. Did you know that pesticide label print is so minuscule that just trying to read it can be frustrating?

If you can decipher the tiny print, you should be able to find out what pests the product will supposedly control effectively. I could find no aphids listed on the label anywhere. If the type of target pest that’s troubling your plants is not on the label, don’t buy it… even if the store clerk says it “should work.”

The label will give instructions for the amount of material to use for application and how to mix it. In addition, the label will provide you with any special precautions you should take to protect yourself, your plants, or wildlife. Even if a material is considered “organic” and relatively benign, it can pose a hazard. Spinosad, as noted on the label, is highly toxic to bees. The label warns not apply it to blooming plants.

Another part of the label that should be heeded is the minimum number of days you must wait from your last application until you harvest the fruits or vegetables. This varies from crop to crop. For example, you must wait seven days to harvest apples after spraying them with this spinosad product, but you only have to wait one day after treating tomatoes. Even if a material is designated as an “organic” material, it doesn’t mean you can eat treated crops right after application. For any type of insecticide or fungicide, check the label when treating food crops for how long you must wait.

This spinosad label also directs you as to the maximum times you may use it in one season on the same plant and the minimum days to wait before reapplying it. These are aimed at preventing insects from building-up resistance to the material.

So what should have the “frustrated” gardener used instead of spinosad to kill aphids on his roses. If he wanted to use an “organic” or less toxic material, I would recommend an insecticidal soap or neem oil product. Thorough coverage of infested plants is crucial in achieving success with these. Since this is a non-food crop, there are other non-organic, more toxic products that will also kill aphids effectively. Products containing acephate, cyfluthrin, or imidacloprid should provide good rose aphid control.

When selecting any pesticide product read the entire label, even though the print is much to small to make this easy. Make sure the pest is listed on the label. Make sure the type of crop or plant is listed on the label. Read and follow all precautions for that product’s safe use in your garden and landscape, whether the material is organic or non-organic. This will protect your garden from pests and you from becoming a frustrated gardener.

Published: 8/14/2010 8:48 AM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

One insect pest plaguing area gardens are aphids. These little suckers must have been awaiting spring just as much as area gardeners. I can imagine them perched next to buds just before new growth emerged, hungrily drooling with wicked smiles on their little faces.

Yes, aphids are little suckers. They have piercing-sucking mouthparts that allow them to pierce plant tissues and tap into sap containing sugars and amino acids. Because the sap is high in sugar content and low in amino acids, the aphids must process large amounts of sap to get the nitrogen they need from the amino acids. They’re not able to utilize all the sugar, so they excrete it as honeydew, a sugary liquid. It’s this “honeydew” excrement that leads to sticky plant leaves and “drippy” trees. In addition to sucking on plant sap, some aphids also inject toxins into the plant tissues on which they are feeding. These toxins cause curled leaves, stunted, and abnormal growth.

It’s amazing how quickly aphids can multiply and become a problem on plants. In just a few weeks a few aphids can become a big problem. Let’s do the math with just one wingless adult female aphid. She is capable of producing 40 to 60 babies. These “babies” mature quickly and in seven to ten days and then start producing baby aphids of their own. In the short span of a few weeks, a dozen aphids can develop into an infestation of thousands of aphids.

Prevent aphids from becoming a big problem by inspecting plants and employing control strategies before their population explodes and causes significant damage to your plants. There are both non-chemical and chemical ways to control aphids:

1. One of the simplest ways to discourage aphids is with a forceful spray of water. Periodic spraying will knock off and kill a number of aphids.

2. Recognize and encourage predators. I’ve already seen ladybird beetle (a.k.a. ladybugs) adults and larvae, syrphid fly (a.k.a. hover flies) larvae, and lacewings at work eating aphids. To protect these beneficial insects, only use “soft” insecticides (such as insecticidal soaps and horticultural oils) that will kill aphids, but leave the beneficial aphid-eating insects alive.

3. There are a number of insecticides on the market that will effectively kill aphids. Some work by direct contact with the aphids. These materials must be sprayed directly on the aphid’s body to be effective. If you use a contact insecticide, keep in mind that most aphids are found on the undersides of the leaves, so be sure to spray the bottoms of leaves too.

Systemic insecticides are sprayed on the leaves and taken into the plant sap, poisoning the aphids as they feed. Some systemics are applied early in the season as a drench to the soil and taken up into the plant by the roots. Systemics applied to the leaves are particularly effective when leaves have already curled around the feeding aphids, protecting them from contact sprays. Before you buy or use an aphid control product, read the label to make sure it can be used on the type of plant where you have an aphid problem. Many systemic insecticides can’t be used on vegetable or fruit crops.

Published: 6/6/2009 9:16 AM



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