Green Mountain Boxwood problems

[MG gal 5]

I have 2 Green Mountain Boxwoods that look terrible this spring.  They are much worse than the typical winter damage that I see on other boxwood in the yard.  They grow in shade and don't get any salt spray.  They seem to be missing a lot of leaves and the leaves at the ends of the branches are peeled open.  I have had leaf miners on other boxwoods in my yard but not on these.  Any ideas?  I will prune heavy and bag the clippings.

[Janet Macunovich 32]

The leaves that are yellow in your picture are all heavily mined so boxwood leaf miner must be at least a part of the problem.

If you've dealt with it before then you know the drill* (remove and hot compost all mined leaves before the weather warms in April, to kill the miners inside before they finish feeding and drop out of the leaf to pupate in the soil; and/or aim to kill the adults when they emerge in late May; and/or protect the new foliage with an insecticide).

 

Great photo! So good that I wonder about whether you've had some help from Nature. At this time of year when it's not yet spring and boxwood leaf miners should still be feeding, I expect to be able to see the miners' silhouettes inside backlit mined leaves... I don't see them. Maybe they're still just that small that I can't see them. Yet I can see the little dots that are their frass/excrement so tininess can't be the issue. I do see what looks like ripped open mined leaves. Have birds  been feeding on the miners? You're there, so you can open a few leaves and look for these buggers. If you don't find many, something has killed them. Woo hoo! Every one gone can mean one less clutch of eggs laid to continue the cycle.

(The tiny orange things are boxwood leaf miner, the larvae of the we-never-invited-it European pest, a gnat-like fly Monarthopalpus flavus.)

 

We don't usually see as much miner damage on this variety of littleleaf boxwood (Buxus sempervirens 'Green Mountain') as other boxwood varieties, but resistance doesn't mean immunity. Could the plants have been more stressed last year, so that the leaves may have been chemically different than usual and more open to attack?

 

*For those who read this who don't "know the drill", take a look at our What's Coming Up #40 (pages 8-9) and What's Coming Up #88 (page 12).

**There are effective  insecticide recommendations in this bulletin from North Carolina Extension. Read the label of the product you're  conisdering using, look for the active ingredient that matches the NCSU list. (This next note is for others, MGgal as I know you know it already). Please don't use insecticides, especially systemic insecticides such as imidacloprid and other neo-nicotinoides, except as a last resort after you have used other tactics. The systemic insecticides poison all parts of a plant including the pollen and nectar -- think bees, butterflies, hummingbirds! -- and if they are applied as a soil drench to be taken up by the roots, affect all the other plants rooted in an area.

[MG gal 5]

Thanks Janet for your help.  The damage on these boxwoods looked like leaf miners but the actual worms are not there like I have seen in the past.  The leaves look "blasted" or peeled open.  These plants are in an area that doesn't get a lot of attention, except for water as there are a couple of hydrangeas planted near by.

 

What puzzles me are the missing leaves below the yellow, dead leaves.  Is is possible that they were damaged by leaf miners last year, fell off and I didn't notice?  The yellow leaves really got my attention this year so I took a closer look.

[Janet Macunovich 32]

I really do think you may have had help from an insectivore. I've seen woodpeckers spend a lot of time poking around in little tufts of leaves, and nuthatches and chickadees. If one of them developed a taste for miners and realized there was a feast to be had there...