- Willow Tree Care and Diseases
- Giant Bark Aphid
- Description of giant bark aphids
- Damage caused by giant bark aphids
- Management of giant bark aphids
- Giant Bark Aphid (Longistigma caryae)
- In the Aphid world, the Giant Bark Aphid has legs that go on for miles and has the honor of being the largest of its kind in North America.
- How to Manage Pests
- Pests in Gardens and Landscapes
Willow Tree Care and Diseases
- “During a terrible rain/wind storm, a huge, old, double oak tree split and came crashing down in my next door neighbor’s driveway. I was given Brian Brunsch’s number at SavATree. They did meticulous work. With the exception of the stump still remaining for insurance evaluation, it doesn’t look like anything happened. A lesson that was learned is to have your trees monitored by a tree expert and SavATree is the company to call.”
Mortgage Professionals, Inc.
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Silver Spring, MD
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New Rochelle, NY
- “Many, many thanks for the work you did at Updike Farm. The care you showed our fruit trees, maples, and ornamental cherries will offer them a chance to recover from years of neglect. With so many challenges facing the Society at the farm, it is reassuring to know that many of the trees have been professionally cared for.”
Gail S., Director
Historical Society of Princeton
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Old Lyme, CT
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J. Todd Lamm
NJ Tree Expert
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- “The only problem I ever had was of the branches that were trimmed, some remained in the tree. The crew came back and got them all out. Ann and co. are all wonderful. I love them and your company.”
- “Let me say that Vassar’s association with SavATree has been very positive and we are achieving great success in managing our campus trees in terms of safety and aesthetics. And our insurance carrier is quite pleased with this effort. Vassar is pleased with SavATree and the work being performed on campus.”
Jeffrey H., Vassar College
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Jerry and Sue F.
- “I am a highly satisfied customer of SavATree. I have never had a tree company that gave me such fine service. I attribute this to my arborist, Scot Boyce. He won me for life as a customer. I asked him to come look at a that was shading my terrace and discuss pruning it, but when he saw how beautiful it was, he advised me to leave the tree alone – a loss of business for your company, but a long term investment in customer loyalty.”
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Pleasantville Country Club Corporation, Inc.
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John K., Southbury, CT
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- “Allan Fenner gave me a mental vision of what the finished product would look like. During the day of the pruning, he came to the site a couple of times to offer further explanation of what the tree climbers were doing at the time and what was to follow. They were all very polite, competent in what they do and truly enjoy their work; the clean-up in front and back was meticulous.”
West Hartford, CT
- “Alan and crew did a tremendous job at our house. With great skill, they removed two large trees, trimmed another tree plus three other smaller projects. Alan engineered the project with with careful attention to safety. I appreciated his friendly helpful manner throughout the day and his willingness to accommodate us. Our thanks to them for a job well done.”
- “It is always a pleasure working with SavATree as your company provides the best plant, tree and lawn health care that we have experienced at the Ives. Always professional, courteous and responsive to our needs, SavATree’s services have provided our employees and patrons with pleasant outdoor experiences in an insect free environment for several years. Not only are SavATree’s treatments most effective but also delivered on time and with the utmost professionalism. In this business the show must go on and SavATree always ensures that it does!”
Kathleen G. Gallagher, Executive Director
The Charles Ives Center for the Arts
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Kimberly and Bruce W.
Cape Cod, MA
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Kristin C., CPO
Evergreen Woods North
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Asbury Park, NJ
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- “For over 14 years, I have entrusted the care of my trees, plants and orchard to SavATree. Their highly qualified arborists have exacting standards and understand how to maintain the health and form of the various species of trees on my property. I admire the artistic skill that goes into the pruning and love the colorful blossoms, fruits and foliage that flourish as a result of their impeccable care.”
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Hyannis Port, MA
- “I continue to work at SavATree because being able to work with true professionals daily to help clients achieve the vision that they desire on their landscapes while growing along with the company and always striving to be the best choice in the industry to service landscapes…that is what drives and motivates me daily and why I choose to have my career at SavATree/SavaLawn.”
- “My wife and I are very pleased with the professionalism and expertise of SavATree. The office manager was pleasant and professional during each of my calls. understood the tree services we needed and was very knowledgeable. Additionally, the professionals who performed the tree services were diligent, efficient and friendly. I would not hesitate to hire SavATree again and recommend their services without reservation.”
Dix Hills, NY
- “SavATree has worked closely with the National Trust for Historic Preservation to save and nurture trees at our historic sites. I appreciate the professionalism and dedication of SavATree’s knowledgeable arborists. Thank you for the work you have done to preserve and enhance the natural landscape of our historic sites.”
National Trust for Historic Preservation
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Cortlandt Manor, NY
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Great Neck, NY
- “SavATree provides the best opportunity in the green industry for growth and great pay to support my family. The job is more challenging than what I was doing before but the workers are supported more here, than at other companies. I also appreciate that the company is more environmentally responsible compared to competitors. ”
- “I have been very happy with SavATree’s services. In particular, their Arbor Patrol program gives me peace of mind knowing that someone is regularly scouting for insect, disease and structural issues before they accelerate and threaten the health of our trees and plantings.”
- “Your support allowed us to provide an affordable community program and appreciation for our Veterans where over 3,000 people from this area came to celebrate the holiday season.”
- “Their arborists are very knowledgeable and make appropriate recommendations to enhance the safety and beauty of our grounds. The SavATree crew pruned, and placed cables and braces in our mature sugar maples which outline our driveway to the club to preserve their life and magnificent presence. SavATree is a professional group, conscientious, on time and easy to work with.”
Timothy J. Strano
Concord Country Club
- “SavATree’s crosscut sawing activity at Historic Hudson Valley’s River Day festival at Van Cortlandt Manor was a wonderful addition to the event and a huge hit with our visitors. As always, your staff did a superb job- the skill with which they interact with the public is just extraordinary. All of us at Historic Hudson Valley are most grateful for SavATree’s partnership.”
Historic Hudson Valley, NY
- “We appreciate the time and attention that your Arbor Patrol team takes to maintain the overall health and appearance of the trees, bushes and general grounds. You can only have one first impression and the impression the grounds make on both residents and visitors alike is always positive. Just as the trees continue to grow and blossom under your care, we hope our relationship with SavATree does the same.”
Chester County Resident
Up in the northern Sierra Nevada, the ecologist Richard Karban is trying to learn an alien language. The sagebrush plants that dot these slopes speak to one another, using words no human knows. Karban, who teaches at the University of California, Davis, is listening in, and he’s beginning to understand what they say.
Original story* reprinted with permission from Quanta Magazine, an editorially independent division of SimonsFoundation.org whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.*The evidence for plant communication is only a few decades old, but in that short time it has leapfrogged from electrifying discovery to decisive debunking to resurrection. Two studies published in 1983 demonstrated that willow trees, poplars and sugar maples can warn each other about insect attacks: Intact, undamaged trees near ones that are infested with hungry bugs begin pumping out bug-repelling chemicals to ward off attack. They somehow know what their neighbors are experiencing, and react to it. The mind-bending implication was that brainless trees could send, receive and interpret messages.
The first few “talking tree” papers quickly were shot down as statistically flawed or too artificial, irrelevant to the real-world war between plants and bugs. Research ground to a halt. But the science of plant communication is now staging a comeback. Rigorous, carefully controlled experiments are overcoming those early criticisms with repeated testing in labs, forests and fields. It’s now well established that when bugs chew leaves, plants respond by releasing volatile organic compounds into the air. By Karban’s last count, 40 out of 48 studies of plant communication confirm that other plants detect these airborne signals and ramp up their production of chemical weapons or other defense mechanisms in response. “The evidence that plants release volatiles when damaged by herbivores is as sure as something in science can be,” said Martin Heil, an ecologist at the Mexican research institute Cinvestav Irapuato. “The evidence that plants can somehow perceive these volatiles and respond with a defense response is also very good.”
Richard Karban, an ecologist at the University of California, Davis, studies how sagebrush communicate.
Plant communication may still be a tiny field, but the people who study it are no longer seen as a lunatic fringe. “It used to be that people wouldn’t even talk to you: ‘Why are you wasting my time with something we’ve already debunked?’” said Karban. “That’s now better for sure.” The debate is no longer whether plants can sense one another’s biochemical messages — they can — but about why and how they do it. Most studies have taken place under controlled lab conditions, so one of the major open questions is to what extent plants use these signals in the wild. The answer could have big implications: Farmers might be able to adapt this chatter, tweaking food plants or agricultural practices so that crops defend themselves better against herbivores. More broadly, the possibility that plants share information raises intriguing questions about what counts as behavior and communication — and why organisms that compete with one another might also see fit to network their knowledge.
Scientists are also exploring how the messages from these signals might spread. Just a few months ago, the plant signaling pioneer Ted Farmer of the University of Lausanne discovered an almost entirely unrecognized way that plants transmit information — with electrical pulses and a system of voltage-based signaling that is eerily reminiscent of the animal nervous system. “It’s pretty spectacular what plants do,” said Farmer. “The more I work on them, the more I’m amazed.”
Farmer’s study doesn’t mean that plants have neurons, or brains, or anything like the systems that animals use to communicate. We don’t do justice to them when we try to put their fascinating, alien biology into human terms, he said. But we may have dramatically underestimated their capabilities. As researchers begin to learn the language of plants, they are starting to get a whole new view of the leafy green world we live in.
Secret Lives ————
Karban started off as a cicada researcher, studying how trees cope with the plague of sap-sucking bugs that descends upon them every 17 years. Back then, the assumption was that plants survived by being tenacious, adapting their physiology to hunker down and suffer through droughts, infestations and other abuse. But in the early 1980s, the University of Washington zoologist David Rhoades was finding evidence that plants actively defend themselves against insects. Masters of synthetic biochemistry, they manufacture and deploy chemical and other weapons that make their foliage less palatable or nutritious, so that hungry bugs go elsewhere. For Karban, this idea was a thrilling surprise — a clue that plants were capable of much more than passive endurance.
How does one leaf know it’s being eaten, and how does it tell other parts of the plant to start manufacturing defensive chemicals? To prove that electrical signals are at work, Ted Farmer’s team placed microelectrodes on the leaves and leaf stalks of Arabidopsis thaliana (a model organism, the plant physiologist’s equivalent of a lab rat) and allowed Egyptian cotton leafworms to feast away. Within seconds, voltage changes in the tissue radiated out from the site of damage toward the stem and beyond. As the waves surged outward, the defensive compound jasmonic acid accumulated, even far from the site of damage. The genes involved in transmitting the electrical signal produce channels in a membrane just inside the plant’s cell walls; the channels maintain electrical potential by regulating the passage of charged ions. These genes are evolutionary analogues to the ion-regulating receptors that animals use to relay sensory signals through the body. “They obviously come from a common ancestor, and are deeply rooted,” Farmer said. “There are lots of interesting parallels. There are far more parallels than differences.”
What Rhoades found next was even more surprising — and controversial. He was looking at how the Sitka willow altered the nutritional quality of its leaves in response to infestation by tent caterpillars and webworms. In the lab, when he fed the insects leaves from infested trees, the worms grew more slowly. But their growth was also stunted when he fed them leaves from undamaged willows that lived near the trees being eaten. The same biochemical change seemed to be happening in both groups of trees, and Rhoades’ conclusion, published in 1983, was that the untouched willows were getting a message from those under attack. That same year, Ian Baldwin and Jack Schultz from Dartmouth University found that seedlings of poplar and sugar maple began pumping out anti-herbivore phenols when placed in a growth chamber next to saplings with shredded leaves. They described it as plant communication. “People were really excited,” said Karban. “The popular press went wild with this.”
That reception made many scientists nervous. The 1979 film “The Secret Life of Plants” (after a 1973 book of the same name) had wowed audiences with time-lapse photography that made plants seem to writhe with vitality as they unfurled their leaves and pushed out roots. The film claimed that science had proven that plants were conscious and could sense human emotions. “It made people think the whole field was hokey,” said Farmer.
Then, in 1984, both talking tree papers were picked apart by the eminent ecologist John Lawton (who was later knighted). Lawton said that Baldwin’s study was poorly designed and that Rhoades must have accidentally spread an insect disease that slowed the bugs’ growth. His criticism nearly stopped the research dead in its tracks. Rhoades, whom Karban calls the “unheralded father of the field,” couldn’t get funding to replicate his studies and eventually quit science to run a bed and breakfast. People stopped talking about plant communication; the field went dark.
Airborne Messages —————–
Not everyone was swayed by Lawton’s criticism. Among the renitent was Ted Farmer, then a postdoc in the Washington State University lab of renowned plant hormone expert Clarence Ryan. Farmer and Ryan worked with local sagebrush, which produce copious amounts of methyl jasmonate, an airborne organic chemical that Ryan thought plants were using to ward off insect herbivores. In their experiment, when damaged sagebrush leaves were put into airtight jars with potted tomato plants, the tomatoes began producing proteinase inhibitors — compounds that harm insects by disrupting their digestion. Interplant communication is real, they said in a 1990 paper: “If such signaling is widespread in nature it could have profound ecological significance.”
When sagebrush is damaged by grasshoppers and other pests, it releases chemicals that seem to warn neighboring plants of danger.
The paper was “enormously carefully conducted, properly replicated and very convincing,” said Karban. But he still had his doubts. Does this really happen among wild plants, or is it an unusual phenomenon induced by lab conditions? Karban had just started work at a field station in a part of northern California that was thick with sagebrush and wild tobacco, a tomato cousin. He repeated Farmer’s experiment in the wild. When he clipped sagebrush plants, imitating the injuries caused by the sharp teeth of insects and inducing the plants to produce methyl jasmonate and other airborne chemicals, the wild tobacco nearby started pumping out the defensive enzyme polyphenol oxidase. This seemed to have real consequences. At the end of the season, these tobacco plants had much less leaf damage than others from grasshoppers and cutworms. Karban cautioned that it’s difficult to say definitely whether the airborne chemicals were directly responsible for the decrease in damage, but the results are nonetheless intriguing.
During the next decade, evidence grew. It turns out almost every green plant that’s been studied releases its own cocktail of volatile chemicals, and many species register and respond to these plumes. For example, the smell of cut grass — a blend of alcohols, aldehydes, ketones and esters — may be pleasant to us but to plants signals danger on the way. Heil has found that when wild-growing lima beans are exposed to volatiles from other lima bean plants being eaten by beetles, they grow faster and resist attack. Compounds released from damaged plants prime the defenses of corn seedlings, so that they later mount a more effective counterattack against beet armyworms. These signals seem to be a universal language: sagebrush induces responses in tobacco; chili peppers and lima beans respond to cucumber emissions, too.
Plants can communicate with insects as well, sending airborne messages that act as distress signals to predatory insects that kill herbivores. Maize attacked by beet armyworms releases a cloud of volatile chemicals that attracts wasps to lay eggs in the caterpillars’ bodies. The emerging picture is that plant-eating bugs, and the insects that feed on them, live in a world we can barely imagine, perfumed by clouds of chemicals rich in information. Ants, microbes, moths, even hummingbirds and tortoises (Farmer checked) all detect and react to these blasts.
Eavesdropping Plants ——————–
Despite the growing evidence that plants are capable of communication, many plant scientists still question whether this cross talk is biologically meaningful. “Interplant communication through volatiles works well in the lab, but nobody’s convincingly shown it works in the field,” said Farmer. Even though he was one of the first to publish evidence that plants are capable of exchanging information, he calls himself a “skeptic” — he thinks there’s not yet enough evidence that this actually plays a significant role in plant lives. “But I wouldn’t want to stop people working on it,” he added. “I think it’s promising and exciting.”
Ian Baldwin, an ecologist at the Max Planck Institute in Germany, thinks we should try to think like plants rather than anthropomorphize them.
C. Diezel / MPI for Chemical Ecology
For both Karban and Heil, the outstanding question is evolutionary: Why should one plant waste energy clueing in its competitors about a danger? They argue that plant communication is a misnomer; it really might just be plant eavesdropping. Rather than using the vascular system to send messages across meters-long distances, maybe plants release volatile chemicals as a faster, smarter way to communicate with themselves — Heil calls it asoliloquy. Other plants can then monitor these puffs of airborne data. Bolstering this theory, most of these chemical signals seem to travel no more than 50 to 100 centimeters, at which range a plant would mostly be signaling itself.
The possibility that plants routinely share information isn’t just intriguing botany; it could be exploited to improve crop resistance to pests. A 2011 report found that commercial corn hybrids seem to have lost the wild maize plant’s ability to release chemicals that attract parasitic wasps that kill stem borer moths. If these defensive traits could be bred back into crops, they could reduce the need for pesticides.Another possibility might be to grow plants with particularly sensitive or potent defensive responses alongside field crops. Like a canary in a coal mine, these sentinels would be the first to detect and react to danger, alerting neighboring crops.
Whether or not such practical applications come to pass, the science of plant talk is challenging long-held definitions of communication and behavior as the sole province of animals. Each discovery erodes what we thought we knew about what plants do and what they can do. To learn what else they’re capable of, we have to stop anthropomorphizing plants, said Baldwin, who is now at the Max Planck Institute in Germany, and try instead to think like them, to phytomorphize ourselves. Imagining what it’s like to be a plant, he said, will be the way to understand how and why they communicate — and make their secret lives a mystery no longer.
Giant Bark Aphid
Description of giant bark aphids
These very large aphids are commonly noticed on the bark of deciduous trees in the late summer. The aphids are grayish black, and found in dense clusters on the bark of 1-3 year old stems on infested trees. The aphids may only be noticed when they become a nuisance by wandering from infested trees or shrubs and onto sidewalks, decks and patios. The aphids leave an iodine-colored stain when crushed.
The giant bark aphid may be found on a variety of trees such as elm, sycamore, oak, maple, basswood, birch, walnut and willow. This is our largest aphid, measuring one-quarter inch in length. Its long legs make it appear even bigger. Giant bark aphid may be found throughout the growing season, but populations are largest and most easily noticed during late summer.
The giant willow aphid is found only on the stems of willow (including pussy willow and Austree). The size is approximately 3/16 of an inch with long legs that make it look even larger. Other than its size the most distinctive feature of this aphid is a large dorsal tubercle (function unknown).
Damage caused by giant bark aphids
Bark aphids feed on sap from inside the twigs. Heavy infestations and severe sap loss may result in stunting or more severe injury including twig dieback. However, otherwise healthy trees often sustain very large populations without any observable affects.
Management of giant bark aphids
Controlling aphids in late summer or fall is usually not warranted. However, observable populations in early summer, especially on young or stressed plants should be controlled. Spraying before the aphids become heavily established will be much more effective. Insecticides are more effective when temperatures are warmer.
Almost all garden and landscape insecticides are appropriate for treating aphids on trees. Common synthetic insecticides such as malathion, Orthene, Sevin permethrin or esfenvalerate could be used, as well as alternative choices such as insecticidal soap or horticultural oil. Check the label of the product you are considering to make sure the tree you intend to spray is listed. Thorough coverage is essential for control. Spray the lower branches of large trees to reduce some of the annoyance wandering aphids will cause, even if the entire tree cannot be treated.
Do you live in Iowa and have an insect you would like identified?
The Iowa State University Plant & Insect Diagnostic Clinic will identify your insect, provide information on what it eats, life cycle, and if it is a pest the best ways to manage them. Please see our website for current forms, fees, and instructions on preserving and mailing insects.
Contact information for each states diagnostic laboratory for U.S. residents. If you live outside of Iowa please do not submit a sample without contacting the Plant & Insect Diagnostic Clinic.
Giant Bark Aphid (Longistigma caryae)
In the Aphid world, the Giant Bark Aphid has legs that go on for miles and has the honor of being the largest of its kind in North America.
Giant Bark Aphids are big as far as aphids are concerned, but they are still small insects. Females may or may not have wings; egg-laying females lack them. Males always have them. The long black wings have small white specks on them, and the red-orange and black legs are quite long. It is easy to mistake one for a mosquito. Mosquitoes are more hump-backed, and they overlap their wings when resting. This aphid has straighter posture and touches just the wing tips together when resting them. The bulbous abdomen is actually black, but it is often covered in a dusty gray or bluish white waxy secretion. This may make the abdomen look like it sports rows of black dots.
This insect only drinks the liquids from trees and is no threat to people. The type of tree greatly varies and is likely based on availability. Hickory, oak, pecan, walnut, sycamore, basswood, elm, maple, birch, chestnut, and willow are all suitable host plants. Females lay yellow fertilized eggs in cracks found in tree bark. These eggs overwinter, turning black as they age. Multiple generations are produced each year, but their feeding is generally not taxing to the tree.
What does create a problem is the sticky, sugar-laden excretion Giant Bark Aphids leave behind. This liquid excrement is called honeydew and it is only related to the melon of the same name because both are sweet. Honeydew gets left all over the tree on leaves, stems, and the trunk. The sugar in honeydew becomes mildewed, turning it black, and this creates a dark, sooty covering on those leaves, stems, and trunk. Before spoiling, honeydew can drip off of tree leaves onto things below it, like cars, patios, furniture, and other things left under a tree’s shade. The subsequent mildew can ruin the finish on cars and patio furniture if left unwashed. For this reason, the Giant Bark Aphid is considered a nuisance.
How to Manage Pests
Pests in Gardens and Landscapes
In this Guideline:
Wingless adults and nymphs of the potato aphid.
Some common aphids
- Aphids on Vegetables and flowers: Table 1
- Aphids on Fruit Trees: Table 2
- Aphids on Woody Ornamentals: Table 3
Woolly apple aphid adults showing waxy coating.
Some aphids overwinter as eggs such as the mealy plum aphid on plums.
Sooty mold, growing on honeydew produced by the hackberry woolly aphid.
Leaf curling caused by rosy apple aphid.
Mummified aphid bodies indicate that they have been parasitized. The parasitic wasp (center) has emerged from the circular hole in the top left mummy.
Aphids are small, soft-bodied insects with long slender mouthparts that they use to pierce stems, leaves, and other tender plant parts and suck out fluids. Almost every plant has one or more aphid species that occasionally feed on it. Many aphid species are difficult to distinguish from one another; however, management of most aphid species is similar.
Aphids have soft pear-shaped bodies with long legs and antennae and may be green, yellow, brown, red, or black depending on the species and the plants they feed on. A few species appear waxy or woolly due to the secretion of a waxy white or gray substance over their body surface. Most species have a pair of tubelike structures called cornicles projecting backward out of the hind end of their body. The presence of cornicles distinguishes aphids from all other insects.
Generally adult aphids are wingless, but most species also occur in winged forms, especially when populations are high or during spring and fall. The ability to produce winged individuals provides the pest with a way to disperse to other plants when the quality of the food source deteriorates.
Although they may be found singly, aphids often feed in dense groups on leaves or stems. Unlike leafhoppers, plant bugs, and certain other insects that might be confused with them, most aphids don’t move rapidly when disturbed.
Aphids have many generations a year. Most aphids in California’s mild climate 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. Young aphids are called nymphs. They molt, shedding their skin about four times before becoming adults. There is no pupal stage. Some species produce sexual forms that mate and produce eggs in fall or winter, providing a more hardy stage to survive harsh weather and the absence of foliage on deciduous plants. In some cases, aphids lay these eggs on an alternative host, usually a perennial plant, for winter survival.
When the weather is warm, many species of aphids can develop from newborn nymph to reproducing adult in seven to eight days. Because each adult aphid can produce up to 80 offspring in a matter of a week, aphid populations can increase with great speed.
Low to moderate numbers of leaf-feeding aphids aren’t usually damaging in gardens or on trees. However, large populations can turn leaves yellow and stunt shoots; aphids can also produce large quantities of a sticky exudate known as honeydew, which often turns black with the growth of a sooty mold fungus. Some aphid species inject a toxin into plants, which causes leaves to curl and further distorts growth. A few species cause gall formations.
Aphids may transmit viruses from plant to plant on certain vegetable and ornamental plants. Squash, cucumber, pumpkin, melon, bean, potato, lettuce, beet, chard, and bok choy are crops that often have aphid-transmitted viruses associated with them. The viruses mottle, yellow, or curl leaves and stunt plant growth. Although losses can be great, they are difficult to prevent by controlling aphids, because infection occurs even when aphid numbers are very low; it takes only a few minutes for the aphid to transmit the virus, while it takes a much longer time to kill the aphid with an insecticide.
A few aphid species attack parts of plants other than leaves and shoots. The lettuce root aphid is a soil dweller that attacks lettuce roots in spring and summer, causing lettuce plants to wilt and occasionally die. In fall, this species often moves to poplar trees, where it overwinters in the egg stage and produces leaf galls in spring. The woolly apple aphid infests woody parts of apple roots and limbs, often near pruning wounds, and can cause overall tree decline if roots are infested for several years. Heavy infestations of crown and root aphids on carrots may weaken tops, causing them to tear off when carrots are harvested.
Although aphids seldom kill a mature plant, the damage they do and unsightly honeydew they generate sometimes warrant control. Consider the nonchemical controls discussed below, as most insecticides will destroy beneficial insects along with the pest. On mature trees, such as in citrus orchards, aphids and the honeydew they produce can provide a valuable food source for beneficial insects.
Check your plants regularly for aphids—at least twice a week when plants are growing rapidly—in order to catch infestations early, so you can knock or hose them off or prune them out. Many species of aphids cause the greatest damage in late spring when temperatures are warm but not hot (65°-80°F). For aphids that cause leaves to curl, once aphid numbers are high and they have begun to distort leaves, it’s often difficult to control these pests, because the curled leaves shelter aphids from insecticides and natural enemies.
Aphids tend to be most prevalent along the upwind edge of the garden and close to other infested plants of the same species, so make a special effort to check these areas. Many aphid species prefer the underside of leaves, so turn leaves over when checking for aphids. On trees, clip off leaves from several areas of the tree. Also check for evidence of natural enemies such as lady beetles, lacewings, syrphid fly larvae, and the mummified skins of parasitized aphids. Look for disease-killed aphids as well; they may appear off color, bloated, flattened, or fuzzy. Substantial numbers of any of these natural control factors can mean the aphid population may be reduced rapidly without the need for treatment.
Ants are often associated with aphid populations, especially on trees and shrubs, and frequently are a clue that an aphid infestation is present. If you see large numbers of ants climbing your tree trunks, check higher up the tree for aphids or other honeydew-producing insects that might be on limbs and leaves. To protect their food source, ants ward off many predators and parasites of aphids. Managing ants is a key component of aphid management. (See Cultural Control.)
In landscape settings, you can monitor aphids by using water-sensitive paper to measure honeydew dripping from a tree. This type of monitoring is of particular interest where there is a low tolerance for dripping honeydew, such as in groups of trees along city streets or in parks and for tall trees where aphid colonies may be located too high to detect. (See Pests of Landscape Trees and Shrubs in References for more details.)
Natural enemies can be very important for controlling aphids, especially in gardens not sprayed with broad-spectrum pesticides (e.g., organophosphates, carbamates, and pyrethroids) that kill natural enemy species as well as pests. Usually natural enemy populations don’t appear in significant numbers until aphids begin to be numerous.
Among the most important natural enemies are various species of parasitic wasps that lay their eggs inside aphids. The skin of the parasitized aphid turns crusty and golden brown, a form called a mummy. The generation time of most parasites is quite short when the weather is warm, so once you begin to see mummies on your plants, the aphid population is likely to be reduced substantially within a week or two.
Many predators also feed on aphids. The most well known are lady beetle adults and larvae, lacewing larvae, soldier beetles, and syrphid fly larvae. Naturally occurring predators work best, especially in garden and landscape situations. For photos and more information about aphid natural enemies, see the Natural Enemies Gallery.
Lady Beetle Releases
Applying commercially available lady beetles (the convergent lady beetle, Hippodamia convergens) may give some temporary control when properly handled, although most of them will disperse from your yard within a few days.
If releasing lady beetles, keep them refrigerated until just before letting them go, doing so at dusk, as those released in broad daylight will fly away immediately. Mist the lady beetles with water just before release, and also mist the surface of the plant you are releasing them onto. Place the lady beetles at the base of infested plants or in the crotches of low branches. Lady beetles will crawl higher into the plant in search of aphids. University of California research indicates that high numbers of lady beetles are required to control aphids. One large, heavily infested rose bush required two applications, spaced a week apart, of about 1,500 lady beetles each. For more information about making lady beetle releases, see UC IPM’s convergent lady beetle page in the Natural Enemies Gallery.
Aphids are very susceptible to fungal diseases when it is humid. These pathogens can kill entire colonies of aphids when conditions are right. Look for dead aphids that have turned reddish or brown; they’ll have a fuzzy, shriveled texture unlike the shiny, bloated, tan-colored mummies that form when aphids are parasitized.
Weather can also impact aphids. Summer heat in the Central Valley and desert areas reduces the populations of many species, and aphid activity is also limited during the coldest part of the year. However, some aphids may be active year-round, especially in the milder, central coastal areas of California.
In some situations ants tend aphids and feed on the honeydew aphids excrete. At the same time, ants protect the aphids from natural enemies. If you see ants crawling up aphid-infested trees or woody plants, put a band of sticky material (e.g., Tanglefoot) around the trunk to prevent ants from climbing up. (Don’t apply sticky material directly to the bark of young or thin-barked trees or to trees that have been severely pruned, as the material may have phytotoxic effects. Wrap the trunk with fabric tree wrap or duct tape and apply sticky material to the wrap.) Alternatively, ant stakes or containerized baits may be used on the ground to control ants without affecting aphids or their natural enemies. Prune out other ant routes such as branches touching buildings, the ground, or other trees.
Before planting vegetables, check surrounding areas for sources of aphids and remove these sources. Some aphids build up on weeds such as sowthistle and mustards, moving onto related crop seedlings after they emerge. On the other hand, these aphid-infested weeds can sometimes provide an early source of aphid natural enemies. Always check transplants for aphids and remove them before planting.
Where aphid populations are localized on a few curled leaves or new shoots, the best control may be to prune out these areas and dispose of them. In large trees, some aphids thrive in the dense inner canopy; pruning out these areas can make the habitat less suitable.
High levels of nitrogen fertilizer favor aphid reproduction, so never use more nitrogen than necessary. Instead, use a less soluble form of nitrogen and apply it in small portions throughout the season rather than all at once. Slow-release fertilizers such as organic fertilizers or urea-based time-release formulations are best.
Because many vegetables are susceptible to serious aphid damage primarily during the seedling stage, reduce losses by growing seedlings under protective covers in the garden, in a greenhouse, or inside and then transplanting them when the seedlings are older and more tolerant of aphid feeding. Protective covers will also prevent transmission of aphid-borne viruses.
Silver-colored reflective mulches have been successfully used to reduce transmission of aphid-borne viruses in summer squash, melon, and other susceptible vegetables. These mulches repel invading aphid populations, reducing their numbers on seedlings and small plants. Another benefit is that yields of vegetables grown on reflective mulches are usually increased by the greater amount of solar energy reflecting onto leaves.
To put a reflective mulch in your garden, remove all weeds and cover beds with mulch. Bury the edges with soil to hold them down. After the mulch is in place, cut or burn 3- to 4-inch diameter holes and plant several seeds or a single transplant in each one. In addition to repelling aphids, leafhoppers, and some other insects, the mulch will enhance crop growth and control weeds. When summertime temperatures get high, however, remove mulches to prevent overheating plants.
Ready-to-use reflective mulch products include silver-colored plastic sold in rolls. You can also make your own by spray-painting construction paper, landscape fabric, or clear plastic. If you use plastic mulches, you will need to use drip irrigation underneath. Landscape fabric and most paper mulches will allow water to flow through.
Another way to reduce aphid populations on sturdy plants is to knock off the insects with a strong spray of water. Most dislodged aphids won’t be able to return to the plant, and their honeydew will be washed off as well. Using water sprays early in the day allows plants to dry off rapidly in the sun and be less susceptible to fungal diseases.
When considering whether to apply insecticides for aphid control, remember that most larger plants can tolerate light to moderate levels of aphids with little damage. Larger aphid populations often rapidly decline due to biological control or when hot temperatures arrive. Often a forceful spray of water or water-soap solution, even on large street trees, when applied with appropriate equipment, will provide sufficient control.
If insecticides are needed, insecticidal soaps and oils are the best choices for most situations. Oils may include petroleum-based horticultural oils or plant-derived oils such as neem or canola oil. These products kill primarily by smothering the aphid, so thorough coverage of infested foliage is required. Apply these materials with a high volume of water, usually a 1 to 2% oil solution in water, and target the underside of leaves as well as the top. Soaps, neem oil, and horticultural oil kill only aphids present on the day they are sprayed, so applications may need to be repeated. Although these materials can kill some natural enemies that are present on the plant and hit by the spray, they leave no toxic residue so they don’t kill natural enemies that migrate in after the spray.
These and other insecticides with contact-only activity are generally ineffective in preventing damage from aphids such as the leaf curl plum aphid or the woolly ash aphid, which are protected by galls or distorted foliage. Also, don’t use soaps or oils on water-stressed plants or when the temperature exceeds 90°F. These materials may be phytotoxic to some plants, so check labels and test the materials on a portion of the foliage several days before applying a full treatment.
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. (On plums dormant applications right after leaves have fallen in early November are preferred.) These treatments won’t give complete control of aphids and probably aren’t justified for aphid control alone but will also control soft scale insects if they are a problem. Common aphid species controlled with these types of oils include the woolly apple aphid, green apple aphid, rosy apple aphid, mealy plum aphid, and black cherry aphid.
Many other insecticides are available to control aphids in the home garden and landscape, including foliar-applied formulations of malathion, permethrin, and acephate (nonfood crops only). While these materials may kill higher numbers of aphids than soaps and oils, their use should be limited, because they also kill the natural enemies that provide long-term control of aphids and other pests, and they are associated with bee kills and environmental problems. Repeated applications of these materials may also result in resistance to the material.
Insecticides such as oils and soaps are also safer to use when children and pets may be present. Formulations combining insecticidal soaps and pyrethrins may provide slightly more knockdown than soaps alone yet have fewer negative impacts on natural enemies than malathion, permethrin, and acephate, because pyrethrins break down very quickly.
Systemic insecticides are also available for aphid management, primarily for woody ornamentals. These materials, including imidacloprid, are very effective and are especially useful for serious infestations of aphids such as the woolly hackberry aphid, which is often not effectively controlled by biological control or less toxic insecticides. Imidacloprid can have negative impacts on predators, parasitoids, and pollinators, so its use should be avoided where soaps and oils will provide adequate control. To protect pollinators, don’t apply imidacloprid or other systemic insecticides to plants in bloom or prior to bloom.
Home-use soil-applied imidacloprid products are often diluted with water in a bucket and poured around the base of the tree or plant. Professional applicators can use soil injectors, which provide better control with less runoff potential. Applications are usually made in spring when aphids first become apparent.
Adequate rain or irrigation is required to move the product through the soil to the roots and up into large trees, and it may take several weeks to see an effect on aphids feeding on leaves. One application on hackberry is enough to control hackberry woolly aphid for two to three years. See Pest Notes: Hackberry Woolly Aphid for more discussion about control methods using imidacloprid.
|Common name||Scientific name||Common hosts|
|Aphis fabae||Legumes, various woody ornamentals, and flowers|
|Brevicoryne brassicae||Cole crops and other mustard family plants|
Green peach aphid
|Myzus persicae||Peppers, spinach, tomato, cucurbits, carrot, lettuce, legumes, corn, flowers, flowering plum, and stone fruit|
Melon (cotton) aphid
|Aphis gossypii||Cucurbits, carrot, citrus, many flowers, and various woody landscape ornamentals|
|Macrosiphum euphorbiae||Potato, spinach, lettuce, tomato, and many others|
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|Common name||Scientific name||Common hosts|
Green apple aphid
|Aphis pomi||Apple, pear, hawthorne, cotoneaster|
Leaf curl plum aphid
|Brachycaudus helichrysi||Plum, prune||Curls leaves, goes to Asteraceae in summer|
Mealy plum aphid
|Hyalopterus pruni||Plum, prune||Curls and stunts leaves, goes to cattails and reeds in summer|
Rosy apple aphid
|Dysaphis plantaginea||Apple||Curls leaves, goes to plantain in summer|
Woolly apple aphid
|Eriosoma lanigerum||Apple, pear, pyracantha, hawthorn||Primarily found on wood or roots, creates galls in roots and waxy deposits|
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|Common name||Scientific name||Common hosts|
Ash leaf curl aphid
|Prociphilus species||Ash (other Prociphilus species attack other trees)||Causes leaves to curl, distort, and form pseudo-galls|
|Sarucallis kahawaluokalani||Crape myrtle|
Giant conifer aphid
|Cinara species||Fir, pine, spruce, cedar||May be mistaken for ticks|
Hackberry woolly aphid
|Shivaphis celti||Hackberry||Produces waxy tufts|
|Aphis nerii||Oleander, milkweed|
WARNING ON THE USE OF PESTICIDES
Pest Notes: Aphids
Author: M. L. Flint, UC Statewide IPM Program and Entomology, UC Davis
Editor: C. Laning
Crapemyrtle aphid photo by Jim Baker, North Carolina State University, Bugwood.org
Produced by University of California Statewide IPM Program
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