Last weekend, I was taking a walk with my husband around our neighborhood and spotted a Weigela in bloom. My first thought was “I have to write about the boxwood leafminer in the email this week.” What?
Boxwood leafminer is a destructive pest of boxwood plants. It is larval stage of a very tiny reddish-orange fly (Diptera). The flies (which look kind of like mosquitoes) can be seen now swarming around the new growth of the boxwoods. They mate and insert their eggs into the undersides of the boxwood leaves and the eggs become the larvae that tunnel on the inside of the leaves. This causes a yellow, blistering effect and can weaken or even kill boxwoods if left untreated. I have peeled back the leaf tissue to view the larvae and have even HEARD them chewing on quiet, sunny days right before they hatch into flies. Ewww!!!
What does all of this have to do with Weigelas? Well, when I first started seeing boxwood leafminer damage, I did a lot of research and was told “there is no organic control for this pest. You have to use systemic poisons.” Well, that is out of the question for this organic gardener so I dug deeper into the life cycle of the pest. It turns out that right now, when the Weigela is in bloom, is the only time it is outside of the leaf. You can spray with Neem or Spinosad and it will kill the adults and any larvae that have just hatched.
Click here http://www.
missouribotanicalgarden.org/ gardens-gardening/your-garden/ help-for-the-home-gardener/ advice-tips-resources/pests- and-problems/insects/flies/ boxwood-leafminer.aspx and link to a really good information sheet on the Boxwood leafminer. It has lots of pictures so you will know what to look for.
Our crews know about this specific, targeted organic spray. They also prune the new growth (after spraying the plant) and collect the clippings, throwing them out in a tightly sealed garbage bag. We have even heard of people go so far as to use a shop vacuum to vacuum up the clippings (which contain the eggs for next year) in order to reduce the population. All of these measures work really well.
The secret to organic pest control is to “KNOW YOUR ENEMY”. By understanding how nature works, we, as humans, can try to outsmart them using safe methods that won’t harm birds, beneficial insects, pollinators, or all the others that we share our yards with. Humans included!