Magnolia scale

Asked August 4, 2020, 8:24 PM EDT

Hello, in looking through the extension website it appears I have a case of magnolia scale on 2 trees. As a result it also appears I have a swarm of wasps, including some nasty looking ones with white heads and tails. I have children and obviously don't want them to get stung. I am wondering what I should do to first remove the wasps (if anything) and of course the magnolia scale. Of course I can't get too close to the trees to treat them because of the wasps! Any help you could provide would be so very helpful. Thank you - Ryan Ries

Ramsey County Minnesota

13 Responses

Thanks for the question.

The picture you sent of the "wasp" was very blurry and hard to see any details. It may not even be a wasp. However if it is, that will affect how you treat the scale. Could you please send us a few more pictures of this insect? You don't need to be real close to it when you do so as we have ways of enlarging pictures. What is important is that the resolution is clear and distinct.

Many thanks.

Thanks for sending the new pictures.

I’m reasonably sure that this is a bald faced hornet . Take a look at the following to see if this looks like the critter you are observing:

https://bugguide.net/node/view/145275

Unfortunately, it is a very dangerous hornet and its stings are extremely painful. They are very social insects building large nests, often in trees. They can be very aggressive. Since you seem to be observing many of these in your trees, it would be safe to assume that they have their nest there. It can be very large. Until we deal with this issue, it would be too dangerous to approach the tree. Whether or not you can see a nest in the tree, at this point you may want to have a professional pest exterminator visit your property to make an assessment. Your specific county was not included in your question so I am unable to direct you to such an individual. This is someone you will need to locate on your own. Please look at the following so that you are aware of the insect you are dealing with:

http://naturemappingfoundation.org/natmap/facts/bald-faced_hornet_712.html

https://www.pestco.com/9-reasons-to-fear-the-bald-faced-hornet/

https://www.rescue.com/latest-buzz/outdoor-pests/bald-faced-bully/

I believe that for the immediate present, you may have to decide between one of two options:

1). Forget about the scale on the magnolia. These wasps (except for the queen) will all die over the coming winter. At that time the nest, if you can find it, can safely be removed. It is not likely that a nest will be built in 2021 in the tree. Deal with the scale issue in 2021.

2). Get a pest exterminator in now and have him/her deal with the situation.

Good Luck!!

Yikes, yeah that looks like the ones. I guess I assumed they were there due to the scale, but you are saying they are probably unrelated? I can't see a nest but then again I'm not getting too close to the trees. And the hornets sure seemed to come out of nowhere. I just don't want to pay to remove them and then have them come right back.

I'm in Ramsey Co if you have any exterminator recommendations. Thank you so much for the prompt responses.

Thanks for the response

I believe that the presence of the wasps is unrelated to the scale. They are more likely going after what’s left of the magnolia flowers.

I understand your concern about cost. Based upon rather limited experience, removal of a tree nest may run close to $400 or more. If you get an exterminator in, usually they will guarantee their work. If the nest can be found and removed, then the queen should be removed as well. If this is done, the wasps will not come back.

As a volunteer University of Minnesota Master Gardener, I cannot recommend any specific commercial service. However in situations similar to yours, I have often suggested the use of the following:

https://www.houzz.com/professionals/pest-control/c/Ramsey-County--MN

Call around. Describe your situation. Ask about a guarantee. Sometimes you can even get a ballpark cost estimate over the phone. Ask if you could receive an on-site free assessment of your situation.

Good Luck!!

Thank you so much for all your help!

Glad to have helped.

Feel free to get back to us again as your situation develops.

Thanks for using this forum.

Well I had a licensed pest exterminator in and he was unable to find a nest in the trees, he suspects that the scale is attracting the hornets (there are also paper wasps present). He says he's never seen anything like this with how many hornets and wasps there are without a nest. So as I was worried about it seems I need to deal with the scale while somehow avoiding the hornets. One tree is right next to my driveway/sidewalk to the front door and one of my kids is allergic so I can't just let it be unfortunately. I know you can't recommend certain companies but are you able to point me in the direction of a resource of specialized horticulturist/arborists/etc that could help with treating/removing the scale? I'm sorry to keep bugging you but I've never dealt with anything like this before.

Thanks for your response. I learned long ago not to be surprised by anything in nature. Give me a day to further research things and then will get back to you.

Thanks.

Further update.

Your exterminator has a point. Turns out (news to me) that scale insects (more specifically “soft scales") produce what is known as honey dew. This is a very sweet substance that attracts a wide variety of insects such as ants, wasps, hornets, and bees. This is probably why there is such a huge number of different insects on your tree. See:

https://powerpestcontrol.ca/magnolia-scale-attracts-wasps-hornets/amp/

So this would also explain the absence of any nest in your tree. The scale insects themselves are a huge insect magnet. We need to return to eliminating the scale. See:

https://www.planetnatural.com/pest-problem-solver/houseplant-pests/scale-control/

https://hortnews.extension.iastate.edu/scale-insects

https://extension.umn.edu/yard-and-garden-insects/scale-insects

Usually scale control consists of removing branches upon which the scale exists. With all the wasps and other critters being there would make this a challenging task. To the best of my knowledge there is not any pesticide that could be applied. So almost but not quite back to square one. If you do nothing now, once temperatures sufficiently cool (late October, early November), the wasps and other insects will disappear. At that time you could prune out all branches having scale on them. Your magnolia tree should not be significantly affected by waiting for another couple months. I understand your reluctance to wait that long.

The other alternative, as you suggested, is to have a professional arborist in to give his/her opinion. If you do this, I don’t know how much new information you would get. She/he might just suggest cutting down the tree and I suspect that would not be acceptable to you. Nevertheless, here is a good publication dealing with locating a professional arborist:

https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional

I have asked a University of Minnesota entomologist to look at our conversations and render an opinion. Will let you know what he says.

It’s a work in progress.

Additional update.

As I’ve researched this further, there are some pesticides available. Some of the links I previously sent you contained information about pesticides. Here is an additional resources:

http://ipm.ucanr.edu/PMG/PESTNOTES/pn7408.html

If you have an arborist out, she/he would be in a good position to speak to you about pesticide application.

Again, work in progress.

Thank you, this is very helpful. The pest professional did apply a pesticide which has reduced but not eliminated the hornets and wasps. He did not expect this would be a permanent solution, may need a re-application. So I am in the process of finding an arborist to come take a look. Maybe I just need to find a hazmat suit and go cut some branches :) The scale looks pretty extensive though including some branches I can't reach from the ground.

Thank you so much for all your help so far, this is definitely a challenging one but I didn't know where else to turn. Very grateful for the expertise!

Thanks. Just keep us apprised.