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Gardening

Notice more wasps and yellow jackets this year? You’re not alone

  • Author: Jeff Lowenfels
    | Alaska gardening
  • Updated: June 4
  • Published June 4

There are two topics of concern this week. The first is the proliferation of yellow jackets and wasps, and the second is the still-increasing number of beetle-killed spruce trees. Both are most troublesome.

Let’s start with the spruce trees. Many are lamenting trees that are starting to turn rusty, and just as many are mourning those trees that already have no needles. There are three aspects to these concerns: what to do to prevent damage to live trees, what to do with dead trees and what to replace the dead trees with.

The beetles are moving into new trees this month. They fly in May, and people are getting notices that their neighbors are spraying trees with pesticides, usually carbaryl or Sevin. My fervent hope is you will have a pleasant conversation with your neighbors and that you are able to talk them out of spraying.

Why? These sprays are harmful to bees and the like, and are toxic to humans. Everyone considering spraying their spruce should read the warning labels before NOT doing it. Second, it may be too late. The beetles have flown, so to speak, and are attacking new trees. Third, the spray has to cover the entire tree and that means a lot of drift. Finally, if your tree is already infested, spraying will not help.

Instead of poison sprays, water your trees when it is dry. Trim the bottom branches so there is good air circulation. Aerate the soil and prevent compaction. As for those dead trees, they need to come down so they do not present a danger..

Finally, we are still struggling with what trees to use as replacements. Personally, I am not in favor of introducing non-native trees to Alaska and urge you to adopt this stance. Non-natives don’t support our birds and insects, which are already under extreme stress. When you lose these, you have really altered things with unknowable consequences.

I have studied and thought about this problem a lot, as I feel a particular responsibility to get this right given that one or two readers actually follow my advice. My conclusion surprises homeowners, but right now, planting young spruce seems to be our best option for several reasons. Spruce are native, so that problem we don’t have to worry about.

Next, there is a relationship between spruce bark beetles and the trees that should not be ignored. Simply put, the beetles actually need some spruce to survive or they will lose their food supply. So, they attack weak and old trees and leave the new ones be. That gives a newly planted, properly maintained spruce something like 20 to 30 years before it is susceptible. If we know we are going to continually have a spruce bark problem, we can stagger planting young trees and do so sooner. In fact, this is something that applies to landscape birches as well as many that are beginning to need replacement due to age.

And, finally, consider that unlike some new, non-native tree species, we know what spruce look like when they are maturing and when they reach old age. There is also plenty of stock at hand, though with global warming it might make sense to start looking for spruce from areas farther south to accommodate the increased warmth we are experiencing — though that is a subject for another column.

OK, now on to wasps and yellow jackets. Readers are complaining about their high numbers this year. My advice? Unless these insects are posing a danger by building a nest near an entry or other place where there is a good amount of human activity, I suggest you leave them be. These are very beneficial insects. They gather other insects to feed their larvae and thus control aphid populations, take out delphinium defoliators and other leaf rollers and so much more. In short, they are usually good news.

It is when they have a nest in the ground — or a paper wasp builds one by a door — that you must be extra careful. These are extremely protective insects and they are known to pursue invaders, even waiting until we come out of hiding! Unlike bees, they don’t lose their stingers when attacking and can sting multiple times. You don’t need me to tell you about stinging yellow jackets.

There are all manner of ways to deal with a yellow jacket nest should you need to remove one. While you can spray nests yourself with commercial sprays or using a recipe from the internet, you may want to contact a professional for particularly complicated situations like a nest way under a porch. Sometimes it pays to have a professional do the work.

Jeff’s Alaska garden calendar

Alaska Botanical Garden: Join! Lots of stuff going on. New plants in the garden shop. Classes and other opportunities. Alaskabg.org.

Get those gardens in: What are you waiting for?

Plant a Row for The Hungry: Now more than ever, we need to make sure we share our bounty. Plant one row, dedicate it to feed someone who needs it and make sure the harvest gets there.

Start second crops: Kohl crops, lettuces, determinate tomatoes

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