disaster at the Pagoda

I go to a certain client's house once a week. Last week I noticed that her Pagoda dogwood (Cornus alternifolia) in the back was missing leaves on the top quarter of the tree. At the time I didn't think much of it; the Japanese beetles have been prolific this year so I assumed it was them and since they haven't done major damage to the other plants I decided to leave things alone.

We all know what happens when we assume.

When I get to a client's house I start off by making a walk-through of the property to get an idea of what needs the most attention this week. The first thing I noticed was that the Pagoda in the front was now missing the top quarter of its leaves. I glanced up and saw groups of insects huddled on the underside of some leaves. Stupid Japanese beetles. I worked my way to the back where the other Pagoda is and stopped short - it was defoliated. Completely. Entirely. That is not the work of Japanese beetles. Upon examination the tree was covered and crawling with yellow and black caterpillars. I went to the Pagoda in the front - it is covered with the same caterpillars. First of all, crap. Second, ew. Third, what are they, and finally, how do I kill them.

The enemy.

Photo from a Google search

I didn't have any bug identifying anything to work with, but I couldn't put off treatment. I mixed up a spray bottle of my Bonide Systemic Insect Control concentrate, put a few of the caterpillars in a plastic bag to id properly later, apologized to any innocent bugs living under the Pagodas, and went to work. It takes a few days for the insecticide to take effect, so I'll check back in a days or two to see how things are progressing and spray again if necessary.

Spraying the back Pagoda wasn't going to do anything for its appearance since the leaves were already gone, but it would prevent the caterpillars from pupating. The front Pagoda still had the majority of its leaves so spraying would - hopefully - keep it looking good. Especially since it's one of the first things you notice coming up the driveway.

Front Pagoda dogwood. The damage can be seen on the two highest branches.

Back Pagoda dogwood.

Later that day I was working near and a little under the back Pagoda. The caterpillars were still crawling around, looking in vain for leaves. I noticed them on the annuals in the containers nearby, and they were crawling across the patio away from the Pagoda. They seemed to be everywhere. Maybe they're escaping the now poisonous Pagoda. Maybe the insecticide is starting to take effect and they've fallen out of the tree. What if they're falling on me? After that every loose piece of hair or funny feeling down my back was a yellow caterpillar. I still get the creepy crawlies.

Once back at the office I did some digging online and discovered that it is an infestation of Dogwood Sawfly. Blasted sawfly. Once I had a name, I could see the similarities between the Dogwood Sawfly and the European Pine Sawfly.

European Pine Sawfly
gray/blue top, green bottom, black head

Dogwood Sawfly
gray/blue top, yellow bottom, black head

  

Dogwood sawfly larva sleeping. This is what at a glance I thought were Japanese beetles.

Just like European Pine Sawfly, the Pagodas won't die from the damage done in one year. Although there may not be time or energy to grow new leaves, the Pagodas may go into an early dormancy. The site said they mainly prefer red-twig dogwoods (Cornus sericea, multiple cultivars). Well, they clearly love Pagoda dogwoods, too.