Zone Five and a Half: WHY ARE MY BOXWOODS BROWN?

The Scourge of Box Tree Moths and Caterpillars. Why are all the boxwoods dying in Michigan?

Within two weeks they were gone. The beautiful boxwood hedges we had planted and nurtured for five years turned brown in a matter of days. The summer was hot and rather dry, but not unsually drought-like. Yet the well established shrubs appeared to be dead.

Ramped up watering, but the patients continued to decline. Nearly all the boxwoods in the neighborhood appeared to be dying, especially those exposed to direct sun.

The culprit--dozens of tiny green caterpillars consumingthe leaves of the bushes, leaving behind a sticky brown mess.

Our kids had begrudgingly planted the baby shrubs for Mother's Day years ago. I was certain the poor shrubs were cooked and lamented the amount of work and cost involved in replacing several hedges.

The lovely shrubs had given pleasure all year long. Their lush greenery sweetened up floral arrangments in the winter and spring. Draped in net lights during the holidays they were magical, especially after a heavy snow. In the summer they added structure to the garden around our old English Tudor.

The culprit was identified as the Box Tree Caterpillar which evolves from a moth encased in a white sticky web-like pod.

Native to Asia, this insect has become a destructive force in Europe. Its larvae are voracious feeders, consuming boxwood leaves and eventually the bark, leading to plant death. The moths hitchhiked their way across the ocean in infested nursery stock/Buxis plants. Now they are eradicating most of the boxwood shrubs in many parts of North America, including Michigan.

The infestation lasts about forty-five days from caterpillar to moth, but most of the damage occurs in the first two weeks.

The yard is looking pretty pathetic between the brown shrubs and the deer damage. Ugg.

How to treat Boxwood Caterpillar Insects?

In mild cases, an early spray of vinegar water may deter the moths from alighting on the shrubs. The most effective method is to spray shrubs early in the summer with Traizicide or Sevin. The bugs immediately disappeared. Unfortunately almost the entire hedge was infested.

The chemistry was effective, but may have waited too long to act.

These are serious chemicals. Be sure to wear rubber gloves, clothing which covers the body and a mask.

Will the boxwoods come back to life?

In our case, we were surprised and relieved to see that most of the heldges are regenerating. There is new green growth on most. So the answer is "wait and see." Trywatering the shrubs at the base nearly every day, but not soaking the plants. An application of Miracle Grow Fertilizer to the plants appeared to encourage growth. Boxwoods do not love acid, so avoid Muracid. There are also fertilizers which are targetted such as Boxus.

They may never come back fully, and it will take at least one season for them to appear normal. Trimming is on hold until late Spring.

The end of one hedge, which receives more direct sun than the others is not regenerating. That section received less water early in the season. It appears stressed boxwoods like these are most vulnerable.

Cautiuosly encouraged, but time will tell. Winters can be challenging in Michigan, even without invasive insects.

Older, more established boxwoods seem more vulnerable.

How to avoid insect damage to boxwoods next year?

There are no plans to excavate any plants except those which have no green growth after several weeks. It's only fair to give the hedgerows a full season to regrow. The strong chemistry eradicated the bugs.

Assuming they survive, the plan is to spray Triazicide in early spring and to be more viligant at the first sign of browning. The caterpillars are tiny and thier color is very similat to the leves of boxwood. They are not easily apparent. A second round will follow if the insects materialise.

Further, halp the shrubs avoid stress by keeping them watered.

Finally, access to light will help the beleagured plants, Trim back overhanging neighbors to allow more light exposure.

Fingers crossed that a gardening crisis may have been averted, but swifter action would have
increased the odds of a positive outcome.

Now if only to find a way to discourage the deer from treating the rest of the yatd as a drive up salad bar!