Boxwood Leafminer
Host: Common Boxwood (Buxus sempervirens)
Symptoms
- Conspicuous egg punctures in leaves. Mines are not evident for several weeks.
- Oval, water-soaked swellings on the lower leaf surface evident from midsummer until shed.
- Infested leaves are spotted yellow and may drop prematurely.
- Continuous infestations result in dead twigs and a weakened plant subject to disease and winterkill.
Description
- Injurious stage: Larva. A yellowish-white maggot, 1/8".
- Monitored/Treatment stage: Adult. A tiny, yellowish-orange midge (fly), 1/10". (Systemics targeted at young larvae)
Life cycle
- One generation annually.
- Overwinters as a partly grown larva in the leaves.
- Grows rapidly in spring, transforming into an orange-colored pupa.
- Emerges as a fly in late May to early June over a period of 10-14 days (300-650 GDD).
- Eggs are laid deep in the upper side of the current season's leaves.
- Female lays an average of 29 eggs and dies hours after last eggs are laid.
- Eggs begin to hatch about 3 weeks after being laid.
Montioring Stage/Timing/Technique:
- Larvae: Inspect for presence November through March.
- Adult: Set out yellow sticky traps or look for swarms early in the morning. 300-650 GDD, end of May through June
- Weigela (Weigela florida) and yellowwood (Cladrastis kentukea [formerly C. lutea]) beginning through end bloom.
- Egg: Check newest leaves for pinholes in late June.
Management
- There are few known natural enemies of the boxwood leafminer.
- Severely shearing the foliage before adult emergence or after egg laying ends will reduce the overall population.
- Plant resistant varieties.
Written by: Robert Childs
Revised: 10/2011
