If you have
boxwoods, you probably know that now is the perfect time to prune them, during
their dormancy. While I was out pruning yesterday I also ran into these fauna:
boxwood leaf miners (Monarthropalpus
flavus).
I have been
learning about them over the last few years but am reading up again as I do
most winters. There is always something to learn. One source says that the Boxwood leaf miner
is most common on American boxwoods, not seen as much on English or Korean boxwoods.
So what do
we know about them? The boxwood leaf miners emerge as adults in late April to
early May depending on the temperatures. The adult is a flying insect which
briefly lives to deposit eggs in the newest flush of spring leaves. Then the
larva grows in the leaf until next spring.
These
creatures were on a series of dwarf boxwoods in a south Nashville garden. There
are large boxwoods on the property, probably English, that showed no signs of
leaf miners.
Here, note
the front and back side of the leaves; both sides look blistered. The affected
leaves are only at the outer several inches of the twigs. Inside the blisters
are larvae which are growing between the leaf’s front and back
surface. If you carefully tear open the leaf, you may find a larva. Or
two. Maybe wiggling. Tiny yellow bits of life.These larvae will
pupate this spring. And start the cycle again.
How bad is
this? Depending on who you ask, not so bad, just an aesthetic buzz-kill. Or they can weaken and kill your plant over
time. I cannot give specific treatment advice, but there’s plenty of research to be found on
chemical controls. I have also heard about a wasp predator, either the Diglyphus isaea or possibly Dacnusa, which might be
worth learning more about.
Happy
pruning!
