Fruit IPM Fact Sheet Fruit IPM Fact Sheet
Rosy Apple Aphid
Dysaphis plantaginea (Passerini)
Adapted from: Common Tree Fruit Pests NCR 63. by: Angus
Howitt, 1993.
Michigan State University
This is an old European species introduced into the United States about 1870. It became a major pest of apples near the end of the 19th century. To thrive, this species must have an abundance of its summer host plant, the narrow-leaved plantain. A remarkable parallelism exists between the introduction and spread of rosy apple aphid and the narrow leaved plantain. This aphid occurs throughout the fruit-growing areas of the United States.
Life Stages
Egg: The egg is oval and slightly flattened on the side next to the bark. The length varies from 0.49 to 0.56 mm. When first laid, it is bright yellow and covered with a glutinous substance that hardens with age. The color gradually changes to greenish yellow and finally to a shiny jet black. The time required for this change in color varies under normal outdoor conditions from about nine days to more than two weeks.
Nymph: The individuals that hatch from the eggs are all viviparous wingless females. There are five instars. The last is the mature stem mother, which shortly after the fourth instar, begins to produce living young parthenogenetically. She produces an average of five to six young per day. The nymphs of the second generation, all of which are females, reach maturity in two to three weeks. The great majority of the nymphs begin to reproduce on apple, though a few may develop wings and migrate to the plantain.
The third generation is produced in June and early July. The majority of this generation develop wings and migrate to the narrow-leaved plantain. In some seasons, wingless females of the third generation produce a fourth generation on apple. In recent years, it has been observed in some areas that damaging populations of rosy apple aphid have persisted in orchards until midsummer or later. It is not known whether this change is due to the selection process, changes of habit or lack of need for an alternative host.
Adult: The adult varies considerably in color markings. The general color is rosy brown, with a pinkish cast due to a powdery covering. Some of the older adults are purple, while the younger adults are decidedly reddish pink.
Host Range
Apple is the preferred host, but the aphid also feeds on pear and hawthorn. Cortland, Golden Delicious, Rhode Island Greening and Ida Red are all particularly susceptible apple varieties. The aphid is found in all fruit-growing areas of the United States and Canada.
Injury or Damage
Rosy apple aphid feeding often causes apple leaves to curl, starting at petal fall. These leaves may later turn bright red. Feeding on the leaves around fruit clusters often results in the bunching, stunting and malformation of the developing fruit. These abnormalities become worse as fruit develops and can eventually render the fruit unsalable.
Large aphid populations may produce large amounts of honeydew as waste from the sap on which they feed. Honeydew excreted onto fruit will serve as a growing ground for sooty mold fungus, which will affect the finish of the apple. Toxins in the aphids' saliva also serve as a "stop drop," preventing the fruits' abscission (natural separation from the tree) at normal harvest.
Factors Affecting Abundance
Untrimmed trees render favorable conditions for the aphids and greatly handicap methods of control. A cool, wet spring favors aphid development because it provides conditions unfavorable for aphid parasites and predators. A large proportion of the overwintering eggs do not hatch. Mortality can be caused by temperature (either low temperature or sudden changes during the winter or during the hatching period); moisture ) cold rains at or just before hatching time, causing young aphids to die before leaving the eggs); predaceous insects and birds that destroy large numbers of eggs during late fall, winter and early spring; and non-fertilization of eggs.
Males are scarce and make up only a small portion of the total population. Many females deposit eggs before mating, and these eggs do not hatch in the spring.
Life History
The aphid passes the winter in the egg stage. Hatching occurs early in the spring, about a
week to 10 days later than the apple grain aphid and at about the same time as the apple
aphid. The eggs hatch when the buds start opening in the spring, over a period of two
weeks. As soon as they hatch, the young seek out the opening buds of the apple; they seem
to prefer the fruit buds. They feed on the outside of the leaf bud and fruit bud clusters
until the leaves begin to unfold. Then they work their way down inside the clusters and
begin sucking the sap from the stems and newly formed fruits.
Their feeding causes the leaves to curl, protecting the aphids from sprays and some enemies. The severe curling of the foliage caused by this species is probably the most characteristic feature of its work. A single stem mother located on the underside of a leaf near the midrib will cause the leaf to fold tightly. It takes only a few stem mothers to cause a severe curling of all leaves surrounding an opening flower bud, providing ideal protection to the rapidly developing aphids. The stem mothers reach maturity when apple trees are coming into bloom.
The mature stem mothers are very inactive. They settle down and feed and produce young at a rapid rate. When distributed, they quickly remove their beaks from plant tissues and seek out another spot in which to continue. The stem mothers mature about two weeks after hatching. The length of time depends largely on weather conditions. The production of young usually begins two or three days after the last molt and continues without interruption for more than a month.
The total production by a single female averages about 185. Normally, the period of reproduction extends from about early May to June. Usually, the maximum period of reproductive activity is around the last week of May and the first week of June, when the young fruits are beginning to set and start active growth. Rosy apple aphid is rarely found attacking the young and rapidly growing shoots. It restricts itself to the foliage, the flower stalks and the young fruits.
One of the characteristic features of this species is the congregation of the young about the mother. Each individual stem mother or group of mothers will have massed about it hundreds of young. The infested leaves may soon be covered-in some cases, by more than one layer of aphids. This habit of congregating soon kills the infested leaves and causes the forced migration of the aphids. The young move actively and hurriedly, seemingly anxious to locate a suitable feeding ground. They are frequently found during this period congregated on the forming fruits or attacking the new, succulent unfolding foliage.
The second generation required four to 40 days to reach maturity and produce young. The majority of the second generation is wingless females. The average total production of each individual in the second generation about 119. The habits and activities of the third generation do not differ from those of the second. The aphids congregate in immense numbers on the undersides of the foliage, causing severe curling. They also attack the setting and developing fruits, producing characteristic injuries.
The majority of this third generation acquires wings and migrates to narrow-leaved plantain, the summer host plant. A fourth generation may be produced. All of these produce wings and migrate to the narrow-leaved plantain. After the last molt, the winged adults are very tender and inactive. They remain secreted in the curled leaves for two or three days before venturing on their migratory flight. Just before flying, they become very active and nervous, running about or moving their wings up and down in anticipation of their flight.
The body of this aphid has a very waxy coating and usually a slight purplish or rosy tinge, which gives it its name. Aphids are on the apples during May and, in smaller numbers, through June and July, though in recent years greater numbers appear to be staying on the apple trees and reproducing in large numbers until later in the summer. They feed and reproduce on the plantain until fall. In the fall, the winged females fly back to the apple trees. Darker than the migrants that left the trees in the spring, these females lay eggs. Males also develop from these eggs. The males mate with the females, after which the females deposit eggs that hatch the following spring. The eggs of the apple grain aphid, apple aphid and rosy aphid are so similar that it is not possible to distinguish one from the others.
Monitoring
Selecting trees such as Golden Delicious that are susceptible to aphids. From tight cluster through petal fall stages, examine 100 fruit clusters in the center of susceptible apple blocks. Treatment is recommended if an average of one colony or more per tree is found in the susceptible varieties.
Control
Apply pre-blossom applications of contact or systemic aphicides. Apply foliage applications of systemic compounds in early season or summer. Early applications, when the aphids are fully exposed and before they curl the leaves, are most effective. Systemic pesticides are required once leaf curling has occurred.
