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Home , Aphid, Brachycaudus helichrysi, Chaitophorus, Macrosiphum

on Shade Trees and

Ornamentals Fact Sheet No. 5.511 Series|Trees & Shrubs by W.S. Cranshaw1 (1/19) Aphids are the most common have intricate body patterning. All aphids Quick Facts found on trees, shrubs, and garden ornamen- are small, ranging from 1.5-5.0mm, with the tal plants. Over 350 different species larger species found on stems and branches. • Aphids are found on almost occur in the state but most can feed on only a Some aphids obscure their body by cover- all types of plants and a few few species of plants. However, with so many ing themselves with waxy threads. These are species can cause plant kinds of aphids, few plants grown in Colo- known as “woolly aphids.” The woolly injury. rado do not support at least one aphid. Most aphid is a common woolly aphid that clusters species rarely injure plants or even attract on the limbs of and crabapples. Aphids • Some aphid species can curl attention, but a few aphid species do cause that cluster within that curl, such as the new leaves of some types problems (Table 1). the leafcurl ash aphid, are wax covered as of plant. Aphids feed by sucking sap from plants. are most aphids that live on plant roots. On • Feeding aphids excrete When the number of aphids on a plant are a related group of insects occur, the , a sticky fluid very high for an extended period, their feed- adelgids, which similarly cover themselves ing can cause wilting and sometimes even with waxy threads. that can cause nuisance dieback of shoots and buds. Some aphids Colonies of aphids often consist of a problems. can cause curling when the insect infests mixture of winged and wingless forms. The • Natural enemies of aphids emerging leaves. great majority of aphids usually develop into include lady , flower fly Sometimes problems with aphids do not the wingless form to remain and reproduce larvae, lacewing larvae, and primarily involve plant injury but instead on the plant. More winged forms tend to be parasitic . their production of sticky honeydew. - produced when colonies get overcrowded, dew is the waste material excreted by aphids plants decline in quality, or environmental • Exposed aphids can be and certain other -sucking insects cues favor dispersal to new plants. controlled by , (e.g., soft scales, , some leafhop- Essentially all aphids, regardless of their insecticidal soaps and pers). It may cover leaves, branches, sidewalks form, are females. Males, if they do occur, are sometimes with a strong jet and anything that lies beneath a infested plant present only in late summer/early autumn, of water. material. Grayish sooty mold grows on the during the last outdoor generation. The nor- honeydew, further detracting from plant ap- mal habit of aphids is for a female to give live pearance. , yellowjacket wasps, flies, and to a genetically identical daughter aphid are usually attracted to plants that are through asexual (parthenogen- covered with honeydew. esis). The newly born aphid can develop rap- idly, typically becoming full-grown in about 10 to14 days. Adults usually can produce Life History and Habits three to five young per day over the course Aphids are small insects that may be of their lifetime, which may extend to about found on leaves, stems and sometimes a month but is usually shortened by natural branches of plants. They have an oval body enemy activities. form and a pair of pipe-like structures There is a shift in the life cycle of aphids to (cornicles) usually can be seen protruding handle the challenge of winter, when plants from the back of the body. Colors are widely are not active and cold temperatures would variable among the different aphid species – be lethal. At the end of the summer, differ- ranging from very pale yellow to dark, nearly ent forms of aphids are produced, including black. Most have shades of green or orange special sexual form males and females. After ©Colorado State University and a few species are even bright red. Upon mating, these females can lay , with they Extension. 4/96. Reviewed 1/19. close inspection, many aphids can be seen to typically lay eggs in crevices around buds or extension.colostate.edu on stems. This is the stage that the aphid 1Colorado State University Extension entomologist and professor, bioagricultural sciences and normally survives winter during outdoor management. 1/19 conditions in Colorado. Eggs hatch the fol- Table 1: Some common aphids associated with trees, shrubs and ornamentals in Colorado. Those marked with an * commonly cause leaf curling distortions in new growth. Scientific name(Common name) Host plant Acyrthosiphum pisum (pea aphid) , other legumes Aphis helianthi (sunflower aphid) Red twig dogwood, yucca and many flowering plants in summer (yellow milkweed aphid) Milkweeds (Asclepias) Aphis spiraecola (spirea aphid) Spirea Aphis viburnicola (snowball aphid) Snowball viburnum Figure 1. Aphids on the underside of an oak leaf. * helichrysi (leafcurl plum aphid) American plum Caveriella aegopodii (-carrot aphid) Various European populicola Chaitophorus populifolii Populus Chaitophorus viminalis Willows spp. (giant aphids) Pines, juniper, spruce * Cryptomyzus ribis (currant aphid) Currant * Dysaphis plantaginea (rosy apple aphid) Apple Dysaphis tulipae (tulip bulb aphid) Dutch iris, tulip Figure 2. Leafcurling produced by aphids on snowball (woolly apple aphid) , apple, crabapple viburnum. * Eriosoma americanum (woolly elm aphid) Elm, Amelanchier/serviceberry Essigella spp. Pines Eulachnus spp. Pines * tataricae (honeysuckle witches’ Tatarian honeysuckle broom aphid) (mealy plum aphid) Prunus rosae (rose aphid) Rose ( aphid) Rose, many flowers

Macrosiphum albifrons (lupine aphid) Lupine Figure 3. Honeydew produced by aphids covering * Meliarhizophagous fraxinifolii (leafcurl ash Green ash oak leaves. Photograph courtesy of Jim Kalisch, University of Nebraska. aphid) Monellia caryae (American walnut aphid) Walnut Myzocallis tiliae (linden aphid) Linden Myzocallis alhambra (western dusky-winged oak Bur oak aphid) Myzocallis ulmifolii (elm leaf aphid) Elm * (black cherry aphid) Tart Cherry * (green peach aphid) Peach, apricot, other Prunus Nasonovia aquilegiae (columbine aphid) Columbine Nearctaphis bakeri (shortbeaked aphid) Hawthorn Figure 4. Sooty mold growing on a wall and walkway underneath a linden tree that is chronically infested Periphyllus lyropictus (Norway aphid) Norway maple with linden aphid. fagi (woolly beech aphid) Beech Pterocomma bicolor Populus Pterocomma smithiae (black willow aphid) Willow cerasifoliae (chokecherry aphid) Chokecherry, pin cherry (water lily aphid) Prunus, various aquatic plants Thecabius lysimachiae (moneywort aphid) Black poplar, moneywort (Lysimachia) (giant willow aphid) Willow sp. Many flowers Figure 5. Yellowjacket feeding on honeydew produced by linden aphid. lowing spring, shortly after bud break, and Table 2: Some common Colorado aphids that alternate between woody and herbaceous hosts. the normal life cycle resumes. Aphid Overwintering Host Summer host Some aphids have even more complicat- Black cherry aphid Woolly elm aphid Wild mustards ed life cycles that involve alternating among host plants. With these species, eggs are laid Currant aphid Currant Wild mustards at the end of the growing season on a tree Green peach aphid Peach, plum, apricot Peppers, , potato, many or shrub (winter host). The eggs hatch on garden plants this plant in the spring and the aphids have Leafcurl plum aphid Plum Various aster-family plants, several generations on this plant. Later, clover, vinca, thistle all winged forms are produced and the leave the winter host and move to feed on Mealy plum aphid Plum Cattail, reeds a different kind of plant (summer host). Potato aphid Rose Potatoes, tomatoes and many The summer hosts of these plants include other garden plants several garden plants and weeds. Some of Rosy apple aphid Apple, pear, mountain-ash Plantain the more common aphids that have host Shortbeaked clover aphid Hawthorn Legumes alternation in Colorado are listed in Table 2. Sunflower aphid Dogwood Sunflower, yucca, parsley, cilantro, pigweed, many other Management herbaceous plants Natural Enemies Thecabius lysimachiae Black poplar Moneywort (Lysimachia) Aphids are quite defenseless and there Water lily aphid Plum, other Prunus Water lily and many other are numerous insects that feed on them aquatic plants (Fact sheet 5.550, Beneficial Insects and Willow-carrot aphid Willow Carrot, parsley, dill Other ). The best known of Woolly elm aphid American elm Serviceberry (roots) these natural enemies are lady beetles, with lady larvae being particularly vora- cious predators of aphids. Other common aphid predators include the larvae of green lacewings and flower (syrphid) flies. Several species of minute stingless wasps parasitize aphids. These wasps insert their eggs into the body of the aphid and the larvae consume it internally. Aphids that have been killed by parasitoid wasps (“aphid mummies”) have a conspicu- Figure 8. Leafcurl ash aphids, a type of woolly aphid. ous appearance, becoming bloated, turning These aphids curl the leaves of green ash. light brown or black and sticking to the plant. Physical and Cultutral Controls On shrubs and garden plants, aphids can sometimes be managed by simply washing them off of plants with a force- Figure 6. Giant willow aphids that develop on willow ful jet of water. Hosing plants may lethally stems are the largest aphids found in Colorado. injure aphids and very few surviving aphids Photograph courtesy of Jim Kalisch, University of that are knocked to the ground can suc- Nebraska. cessfully find their way back onto their host Figure 9. Aphid on cottonwood giving live birth to a plant. daughter aphid. Some flowers that are perennial, but dieback to the ground in fall, have prob- lems with aphids in the spring. Columbine, lupines and perennial asters are examples. With these plants the eggs of the aphids are laid on the leaves and stems in fall. The eggs hatch in spring and if new growth has emerged at that time some of the newly Figure 10. Winged and wingless forms of the green hatched aphids can make it to the growing peach aphid. plant. This can be prevented by removing the old top growth that contains the eggs Figure 7. Colony of aphids on the leaves of willow. before plants emerge in spring. This plant synthetic derivatives of the natural product material can then be safely composted or pyrethrins, which is extracted from flowers piled elsewhere as any aphids that hatch of the daisy/Dalmatian daisy.) from the eggs will only be able to move very can be identified by looking short distances (inches) before dying. at the active ingredients. Those that end in “thrin” are some : bifenthrin, Chemical Controls cypermethrin, cyhalothrin, cyfluthrin, per- Where high numbers of aphids regu- methrin. None of these move systemically larly occur and injure plants or outbreaks in the plant so they are not effective for are not sufficiently controlled by biological aphids present in curled leaves. Malathion controls, insecticides can be used to man- is another that can kill aphids on Figure 11. Eggs of the Norway maple aphid tucked contact, although its availability is dimin- around the base of buds. Photograph courtesy of Ken age aphids. These are used in several ways. Gray Collection, Oregon State University. Dormant Season Oil Applications. ishing. Horticultural oils (Fact sheet 5.569, Insect Because of their persistence these Control: Horticultural Oils) have a special insecticides may give better initial control place in aphid control, to kill egg stages of aphids than a non-persistent insecticide. during the dormant season. Horticultural However, they can have serious effects on oils act largely by smothering insects their the natural enemies of aphids, which may use for aphid control would require that diminish longer term control. Persistent they cover the eggs, which are the overwin- insecticides cannot be applied to plants that tering stage on some kinds of aphids on are in bloom and being visited by bees. trees and shrubs. They would be applied as Systemic Insecticide Sprays. A few sprays sometime before bud break, during types of insecticides have the ability to the dormant season. move into the plant and move systemically. Most aphids on fruit trees, aspen/pop- Because of this mobility these systemic lars, willows, poplars, pines, rose, lindens, insecticides can provide better plant cover- , oaks, hawthorn and viburnum age and often provide better control of survive winter as eggs on the plant and can aphids than do non-systemic insecticides. be controlled with horticultural oils. Other Systemic insecticides are also able to kill aphids, such as the leafcurling aphids on aphids that are protected within a leaf they Figures12a-b. Adult (a) and (b) of a lady beetle ash, do not survive winter in this stage and have curled. Acetamiprid and cannot be controlled with horticultural oils. are the active ingredients of systemic insec- Non-persistent Contact Insecticide ticides can purchase and use as Sprays. Insecticidal soaps and pyrethrins are spray. Both may continue to kill insects for two commonly available and popular insec- a couple of days to a couple of weeks after ticides that can be used to control aphids. application. Neither of these persists for long (minutes Sprays of systemic insecticides come to hours) on the foliage. Only insects that with the same limitations as the non- are covered with sprays during application systemic persistent insecticides mentioned can be killed with these types of products. above – they may kill natural enemies of Neither will move systemically in the plant aphids and pose risks to pollinators if ap- and they cannot control aphids that have plied to plants in bloom. curled leaves and cannot be reached with Soil-Applied Systemic Insecticides. sprays. The systemic insecticideimidacloprid A main advantage of both insecticidal can be applied to the soil where it may soaps and pyrethrins is that they are selec- be picked up by plant roots then moved tive in their effects, posing minimal hazard through the plant, concentrating in the to beneficial insects (e.g. pollinators, natural newer leaves. This insecticide is widely Figures 3a-b. Larvae of a green lacewing (a) and a enemies of pests) and have very low toxicity available at retail and sold under several dif- flower fly (b) to mammals and birds. ferent trade names. In some formulations Persistent Contact Insecticide Sprays. used on trees it is combined with a second Many of the insecticides sold at retail stores systemic insecticide, chlothianidan. will persist for awhile in their ability to kill These insecticides are normally mixed aphids – and other insects. Some may be with water, then poured around the base able to continue to kill insects for several of the plant. If mulch is present over the hours, some for several days. treated area, that must be removed before Most of these types of insecticides found application, but can then be replaced. After application the soil needs to be kept a bit on for sale to control aphids are some type Figure 14. Adult of a next to two of pyrethroid insecticide. (Pyrethroids are moist to allow the insecticide to move to aphid mummies. and be absorbed by roots. There will be some delay between the time of application and when insects will be killed by a soil application of imidacloprid. Normally this will take a couple of weeks if conditions are suitable for root uptake (warm tempera- tures, moist soil). Once the insecticide has moved within the plant these treatments will usually be able to kill aphids – and other susceptible insects – for several weeks, perhaps a couple of months. This long persistence can provide very good aphid control. How- ever, it also can increase potential to harm beneficial insects. At particular risk are insects that feed on pollen and nectar, such as bees and some insect natural enemies, since imidacloprid can occur in pollen and nectar. To prevent injury to pollinators, soil- applied systemic insecticides should not be applied to plants that are flowering or soon will be flowering.

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