Magnolia Scale Treatment – Timing is Everything

Our customers have noticed that we are starting treatment for Magnolia Scale later than usual this year. In the past, we generally the first application occurred in late September. We based our application timing on everything we had read and were told by leading entomologists who study the lifecycles of these insects.

‘Scale insects’ are very difficult to control in general but especially Magnolia Scale. Instead of going with the conventional wisdom for when to treat these trees in our temperate zone, we decided to get a little more scientific.

If you really want to know what our game plan is, and why, please read on.

The Life Cycle of Magnolia Scale

The white and grey pods that you see on the branches of trees were created by a single female Magnolia Scale adult. She formed that pod in the Spring, stayed inside it all Summer before giving birth to hundreds of baby crawlers. Once she gives birth, the female adult dies within the pod. These baby crawlers are almost microscopic when they hatch and live within the pod, feeding off of the carcass of the deceased female. (We know, kind of graphic). The crawlers will slowly begin to emerge from the pod late Summer through early Fall.


photo courtesy of Joe Boggs

This had us wondering; How long does it take for all of the crawlers to emerge from within the pod? A few days, a week or a month? Since the insecticide sprays will work best if we spray once ALL of the crawlers have emerged, this seemed like an important thing to know. None of the experts that we talked to seemed to know the answer to that question.

So, Tree Green purchased a powerful microscope of our own to see exactly what was going on with these crawlers first hand. We noticed that some of the crawlers were indeed out from their pods in August and we wondered if we actually needed to start spraying earlier than we had in prior years. Once we flaked some of the pods open however, you could see under the microscope that there were still more crawlers concealed beneath the pod. Then we re-checked every week and to our surprise there were still crawlers feeding within the pods.  Our most recent check was the other day, October 3rd. Granted there were fewer crawlers under the pods and had we sprayed, some would have been protected.

Photo: Rutgers Cooperative Extension

Photo: Rutgers Cooperative Extension

Once these crawlers emerge from the pods, we are told they do not go back inside. They live on the tree or travel to other area Magnolia trees. The crawlers go dormant when temperatures drop below freezing over the Winter. Once Spring comes, the baby females grow, mate and begin making those pods all over again, repeating the cycle.

We are waiting until our microscope tells us that most, if not all of the crawlers, have emerged. There are many factors that could influence emergence however. Certain neighborhoods may be affected differently from others and tree exposure to sun and shade is different from property to property.  We are doing our very best to monitor these insects and take into account these varying factors to choose the best time to begin spray applications.

Insect and disease control is not an exact science so one year might be different from the last. This year we might start in mid-October and next year, late September. The type of Spring, Summer and Fall that we have changes from year to year, and with that, so changes the cycle of living organisms.

We know of no other company who takes the measures that we do to ensure the best possible service delivered at the most opportune and effective times. We pride ourselves on that fact and thank you for continuing to trust Tree Green with your tree care!