Question
Hi,
I sure hope you can help me out with an answer to the the stinging insects that are swarming my tree.  I have an older, largish (about 10 - 11 foot high) star magnolia that is infested with magnolia scale.  I have 2 treatments scheduled with an arborist in the fall.  The first treatment is with an insecticide/light horticultural oil spray treatment in early September and the second a fall horticultural oil sprayed later in the fall in the dormant season.
A friend in the business recommended using Merit as a soil treatment now.

My question really involves the enormous and numerous hornets and wasps that are swarming my tree.  Is there anything I can do to repel or get rid of these stinging insects NOW?  Will the Merit applied now have any effect on them?  Will it hurt the squirrels that are eating the magnolia fruits now?

I really didn't want to use the soil insecticide but the combination of the scale (which is damaging my tree and all the plants under it) and the hornets and wasps is making me desperate.

I'm terrified of the hornets/wasps and this tree is right next to my front door and gate to my yard.

Is there anything I can do now to get rid of them???

At this point, I'll apply anything.  I sure hope you can help.

Thanks very much,

Debbie

Answer
Debbie,

Just to review, the wasps are swarming because of the sweet honeydew that is being secreted by the scale insects that are feeding on your magnolia tree. If you could get rid of the scale insects and/or the honeydew the wasps would go away. The problem is there's probably not much you can do this year about the scale insects. The treatments you describe will work but are slow acting. Even the Merit Insecticides takes a long time to be effective against adult scale insects. Next year your scale insect/wasp situation should be better.

For this year your only real option is to try and remove as much honeydew as possible from the leaves and thus reduce the tree's attractiveness to wasps. You can do this with a spray of water from a garden hose alone or a combination of water and insecticidal soap. I'd use both. Thoroughly wet the tree with water from a hose then treat with insecticidal soap from a garden sprayer, which will help dislodge the honeydew, wait 30 minutes then spray the tree throughly with water again to remove the soap and honeydew. You may need to do this treatment once a week for the rest of the summer. The good news is insecticidal soap is very low toxicity and easy to use.

Here's an article about using insecticidal soap for aphids, spider mites and scale insects http://www.livingwithbugs.com/insecticidal_soap.html that may be useful.

Post a follow up if you have questions about this procedure.

Jack DeAngelis, PhD
Extension Entomologist (ret.)
My website about home and garden pests: http://www.livingwithbugs.com