In recent years, honeysuckle shrubs have become prone to infestations of the honeysuckle aphid (Hyadaphis tataricae), whose feeding habits cause a serious distortion of growing tips known as “witches’ brooms.” While attacks from the honeysuckle aphid do not usually kill the plant, the production of witches’ brooms can decrease its overall health and greatly reduce its aesthetic value.
Growing to less than 1/16 inch in length and varying from a pale green to cream in color, the honeysuckle aphid can easily be missed during routine plant inspections. To aid in proper identification, look for a dark head and thorax and a white abdomen, which is often covered with a fine, powdery dust.
The aphid’s entire life cycle is completed on the host plant. As a non-migratory species, the honeysuckle aphid overwinters its eggs, preferably on buds and branch tips of previously infested plants. In early spring, just as new leaves are emerging, these eggs hatch, bearing the first of several generations that will be produced continuously throughout the summer. Initially, only wingless females develop, but in late summer, winged males and wingless females are born, at which time they mate and deposit their eggs on the shrub. In late summer, when the population of aphid colonies can reach in the hundreds, they can be found outside the damaged, curled leaves feeding on petioles and stems. Generally, adult aphids remain inside the folded leaves where they are protected from weather and predators.
The curled and dwarfed leaves, which result from early feeding, are typical of aphid damage. The aphids’ salivary secretions cause the stunting of both leaf and stem growth. As the season progresses and more generations are born, the destruction will involve several inches of the branches, resulting in small and weakened side shoots known as “witches’ brooms.” In autumn, the leaves on the witches’ brooms usually will turn brown and die before the shrub would normally produce its fall color. Often the damage inflicted throughout the season does not become noticeable until winter when remnants of the dead foliage and the unsightly witches’ brooms are more apparent.
While the damage done by the honeysuckle aphid is mostly aesthetic, the repeated production of witches’ brooms can diminish the host plant’s vitality, making it susceptible to other insects and diseases. The degree of injury varies between species and cultivars of honeysuckle (Lonicera spp.), however, Lonicera x. xylosteoides ‘Clavey’s Dwarf’ and Lonicera tatarica ‘Arnold Red’ are resistant. Planting of these species is not recommended as they are invasive in many areas.
As with other species of aphids, lady beetles will prey upon honeysuckle aphids in their adult and larval stages and, by late summer, many aphids will have been eaten by these natural predators. However, winged aphids can easily be blown in all summer to re-infest plants and deposit eggs for overwintering.
Removing infested branches 6 inches below any witches’ brooms remaining from the previous season can be an effective method of control. Do this during the winter while the plant is dormant or in early spring before the eggs have hatched. This will not only remove the unsightly witches’ broom, but will also help reduce the severity of future attacks by eliminating most of the early season population. Any pruning done after the eggs have hatched may result in fresh leaf growth, which is then susceptible to further aphid damage. In general, cultural practices that encourage the production of new plant growth can intensify aphid problems. It is often found that improperly pruned, irrigated, and over-fertilized plants have the highest aphid populations.
The successful application of any chemical measure is dependent upon an understanding of the aphids’ life cycle and attentive observation of the shrubs throughout the season, for often by the time any damage is noted, it is late in the summer and no insects remain with the injury. The best time to begin a spray control program is in the spring when the new leaves are developing and before the newly-hatched aphids begin their feeding cycle.
Contact the Plant Clinic (630-719-2424 or firstname.lastname@example.org) for current recommendations. Use pesticides safely and wisely; read and follow label directions. The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.