Boxwood Leaf Miner - Monarthropalpus flavus

My eyes were drawn to my small Korean Boxwood yesterday. This variety is called "Green Gem". I bought it 3 years ago. It had some winter snow (weight) damage on it earlier this spring, but something else caught my attention.

Seeing these brown blisters frustrates me.

Tucked inside these blisters is a creature called: 
Monarthropalpus flavus - Boxwood Leaf Miner

As you can see, pretty much all the leaves have blisters in various stages of  the leaf miner's life cycle.

Here, I brought a stem inside to reveal what's inside each blister pocket. 

The adult leaf miner lays eggs, by inserting them between the layers of the boxwood leaf. Making a perfect pocket situation for their offspring to hatch, become pupae and begin feeding.

Here you can see the small puncture hole mark, 
where the adult laid the egg. This hole becomes the exit for when they pupate into adults.

Some leaves have 3-4 miners munching away. Getting ready to become adults.

On the shiny, upright part of the leaf, you see more browning and damage. Holding this up to the light will reveal the pupae, its excrement and the ever enlarging pocket they create.

These photos show pupae that are orange, this means they are near ready to transform themselves into adults. The pupae are lighter in colour when young - more yellow. Once they become orange, this is the time they stop feeding and go through their next life cycle. Through the puncture "window" or hole, they will squeeze through, hang from upside down until they pupate into an adult - orange fly.

This is an insect that is hard to control, unless you cut back the blistered portions of the boxwood ruthlessly or if you use pesticides. Systemic insecticides would help me combat this insect, but for such a small plant and for the sake of spraying chemicals, I choose not to in this case. In Ontario, one would require a pesticide license to acquire such chemicals to do the trick.

Since this is a young boxwood, I have decided to take it out of my garden. If I prune it back hard, it will take a long time to recover and my garden is too small to waste space. Last year the leaf miner numbers were unnoticeable to me. Perhaps I purchased this boxwood with leaf miners or perhaps not. Best rid this boxwood before it feeds off my other plants.

So sad.... Time for something else in that spot.

Have a look at my post on the adult-life-cycle of this Leaf Miner.

Cupped Boxwood Leaves - Boxwood psyllids

Have you ever seen boxwood leaves cupped and curled like this?

These leaves have curled because of a sap sucking insect called, psyllids. Boxwood pysllids (Psylla buxi) sort of resemble aphids as nymphs - with size and colour. There's usually one generation a year and control is best with an insecticidal soap application in late spring (May in Ontario). Treat when the new growth of leaves fully open. Psyllids don't kill boxwood, but will distort and affect the foliage - aesthetically ruining the glossy look to this broadleaf evergreen. 

In these photos, you can see remnants of their past presence. Their feeding has cupped the foliage right over the bud tips. Causing the tip of the stems to wither and dry up.

You can also see remnants of their excrement - a white residue.

When psyllids nymphs are high in number, you may see their white, waxy excretion before the leaves curl. Usually at the tip of the branch stem. As they feed, the boxwood leaves respond by cupping - sheltering them, where you don't see the nymphs at all. Psyllids usually feed on young, new growth that is tender. Hence the reason the leaves curl so easily.

Their white frass (poop) is quite fluffy and insulates them as they feed toward the bud union of the leaf.

Psyllids have flat bodies, with large eyes. I wish my camera could take a better photo, but you get the idea on how small they are compared to my fingers.

Psyllids lay orange eggs between the bud scales. As the leaves emerge from the buds, the eggs mature and hatch into nymphs - then the feeding begins. Nymphs become a flying winged adults (which look like miniature cicadas) in June and reproduce, laying the eggs near the terminal buds for next years cycle.

I've found you can reduce psyllid numbers drastically with just water. A high pressure spray dislodges many of them and reduces the adult population. Just be aware, adults may be blown off and fly back. So the spray of water needs to be repeated and quite high in pressure.

Not a huge problem, but easily treated.

Above are photos of other notable boxwood characteristics that have confused folks often. These are boxwood flowers (left) and last years seed husks. I've had folks ask me if the right photo is a disease. ;)