Recognize Boxwood Leafminer - Eliminate This Harmful Insect on Your Boxwood
The boxwood leafminer (Monarthropalpus flavus), a common pest on cultivated boxwood shrubs, can pose a significant threat to the life of the plant. Here's what you need to know about identifying, preventing, and treating boxwood leafminer infestations.
In spring, the life cycle of the boxwood leafminer begins as the females insert eggs directly into the boxwood leaves from the undersides. Early signs of an infestation include light green or yellow spots on the upper sides of leaves. As the infestation continues, it can cause crinkled, yellow, or brown blisters on the undersides of leaves, slight elevations on the upper leaf surfaces, distorted leaf structure and shape, transparent circular spots, leaf browning, leaf drop, and damage to the plant.
Caring for boxwood and keeping plants healthy and thriving is the best prevention against boxwood leafminer. Regular pruning, good irrigation and drainage, and appropriate fertilizer are important for maintaining healthy boxwood. Choosing boxwood cultivars that are less susceptible to leafminers can also help prevent infestations. Examples include Japonica, Green Pillow, or Franklin's Gem for Buxus microphylla, and Argenteo-variegata, Pendula, Suffruticosa, and Vardar Valley for Buxus sempervirens.
If a boxwood is completely brown from leafminer, it probably won't recover, but removing the most damaged branches and applying chemical controls might allow it to recover the following year. The best time for chemical control against boxwood leafminer is as the adults emerge from the leaves in early spring. Products with bifenthrin, carbaryl, cyfluthrin, or malathion can be used for chemical control. A systemic insecticide like imidacloprid is often effective against boxwood leafminer.
However, it's important to note that neem oil, while moderately effective against boxwood leafminers, generally works better as part of an integrated pest management (IPM) strategy rather than as a sole long-term control. Neem oil disrupts leafminer feeding and development but has short residual activity. Repeated applications (weekly) during leafminer activity are necessary for meaningful control. Neem oil benefits include lower toxicity and less impact on natural enemies.
To improve control of boxwood leafminers, neem oil should be used alongside cultural tactics (e.g., pruning infected leaves, ensuring good plant health) and potentially supplemented with systemic insecticides if infestations are severe. It's also worth noting that such treatments usually require certified applicators.
Natural predators such as green lacewing, if introduced in your yard, could potentially curb boxwood leafminer infestations.
In summary, early detection and prompt action are key to managing boxwood leafminer infestations. A combination of cultural practices, chemical controls, and the use of natural predators can help keep your boxwood healthy and thriving.
Incorporating a home-and-garden lifestyle that includes regular gardening can help prevent boxwood leafminer infestations, as this routine encourages healthy plant growth. To keep boxwood plants resilient against pests like the boxwood leafminer, consider cultivating boxwood varieties like Japonica, Green Pillow, or Franklin's Gem for Buxus microphylla, and Argenteo-variegata, Pendula, Suffruticosa, and Vardar Valley for Buxus sempervirens.
