Pests of Boxwoods

Boxwood Leafminers

Boxwood leafminers feed and develop within plant leaves. Heavily mined leaves usually turn yellow and may drop prematurely, but the leaf drop usually doesn’t have a significant impact on otherwise healthy plants.

Figure 1. Light areas on undersides of leaves are signs of boxwood leafminer activity. (Photo: Lee Townsend, UK)

Figure 2. Lower leaf tissue were removed from this leaf in order to show the boxwood leafminer larva (a maggot). The insect pupates and the adult (a small gnat) emerges in late April to early May. (Photo: Lee Townsend, UK)

Management

Natural enemies can be effective in managing infestations. If this insect has been a problem, application of insecticides such as carbaryl (Sevin), cyfluthrin (Bayer Multi-Insect Killer Concentrate, or permethrin (Bonide Borer Miner Killer, and others) about the time of Weigela bloom should provide preventive control. Products containing acephate (Orthene and others) can give some control if mines are developing.

Boxwood Psyllids

Boxwood psyllids are flat, green, sap-feeding insects that cause spring terminal growth to cup (Figure 3). The damage is especially noticeable on American boxwood. While the small nymphs (Figure 4) blend well with the foliage, the white waxy strands that they produce are very easy to see (Figure 5). These insects affect the appearance of the plant but are not a threat to plant health or vigor. Fortunately, distorted leaves usually fall off in about a year and the plants can recover. More information is available in Boxwood Psyllids (EntFact-454)

Figure 3. Cupped leaves are a classic symptom of boxwood psyllids. (Photo: Lee Townsend, UK)

Figure 4. Psyllid nymph with white exudate visible on its abdomen. (Photo: Lee Townsend, UK)

Figure 5. Psyllids with white waxy strands visible between cupped leaves. (Photo: Lee Townsend, UK)

 

By Lee Townsend, Extension Entomologist

 

 

 

 

Posted in Landscape Trees & Shrubs