Boxwood Leafminer (Monarthropalpus flavus)
GDD Window (base 50): 290+ (adult emergence), 448-700 (larvae emergence)
Overview:
- Overwinters in the leaves as larvae
- Larvae are bright yellow or orange and become active in spring, feeding on leaves from the inside, creating yellow or brown blisters which become clear as larvae grows, making the leaf swell and look puffy
- Heavily infested leaves sound like they’re crackling
- Blistered leaves weaken the plant and cause leaf drop, plants appear sparse
- Gnat-looking adults emerge by early summer and are yellow-orange in color, leaving behind a pinprick-sides hole in the underside of the leaf
- Females lay eggs on upper surface of new leaves
- Eggs hatch and larvae mine leaves throughout summer
- One generation per year
- Host plants: Boxwoods
Management:
Cultural Practices:
- Natural predators: lacewings, ladybugs, hover-flies, parasitic wasps, spiders, birds
- Companion plantings: lavender, marigolds
- Monitor throughout the season, sticky traps
- Reduce plant stress
- Choose resistant varieties
- Manually crush insects
- Heavy pruning for first-year growth after egg-laying in early summer
- Destroy clippings
Materials:
- Contact insecticides:
- Avermectins [6]: abamectin
- Pyrethroids [3]: -thrins
- Carbamates [1A]: carbaryl
- Systemic insecticides:
- Organophosphates [1B]: acephate (translaminar);
- Neonicotinoids [4A]: imidacloprid, dinotefuran, clothianidin, acetamiprid
- Considerations:
- Contact insecticide application must be timed with the emergence of adult flies
Biorationals:
- Insecticidal soap
- Horticultural oils
- Insect growth regulator: Pyridayl [UN]: azadirachtin
- Spinosyns [5]: spinosad
Disclaimer – Materials do not cover all possible control scenarios and are intended for licensed professionals. Tradenames do not imply endorsement and are used as examples. You must strictly follow the label for each compound prior to use. Rutgers is not responsible form is used materials or damages thereof. The label is the law. Labels will provide detailed information on use and restrictions. Additionally, application intervals, compatibility, surfactant use, PHI, PPE, important and other key information is described in detail. Always discuss treatments with your local agents. Note: Neonicotinoids can only be legally applied in commercial agriculture settings by licensed applicators. Guidelines and recommendations made in this presentation are specific to the state of New Jersey.