Garden Tips: Elm Seed bugs annoy us — again

The elm seed bug is being a real pest again this summer in some Mid-Columbia homes.

The folks most likely to be bothered by this little bug are those with an elm tree in their yard or growing nearby.

Because they are flat and small — only 1/3 of an inch — they easily gain access into homes through tiny gaps around windows, doors, vents and plumbing conduits.

Elm seed bugs are primarily a nuisance. They feed on elm seeds and leaves with their piercing-sucking mouthparts. The feeding does not cause any noteworthy damage to the tree.

What “bugs” people is the invasion of their homes by large numbers of elm seed bugs that are trying to escape the summer heat and sun.

They do not infest foods, damage furniture or bite humans. However, they may leave small fecal deposits in the form of brownish spots around window frames.

Inside your home, controlling the bugs is as simple as vacuuming them up and immediately disposing of them in a sealed plastic bag.

It is important to note that elm seed bugs, like many other seed bugs, release a repugnant smell when crushed so I suggest you refrain from squashing them.

The first line of defense should be around windows and doors, especially sliding glass doors and windows which are their favored avenues for coming inside. If scads of bugs are finding their way indoors, consider using caulking, weather stripping or placing removable tape around windows and doors.

If your elm seed bug problem is overwhelming, you might want to control them at the source. Many of the elms growing in this region are Siberian elms (Ulmus pumila) that planted themselves and were allowed to grow.

The Siberian elm is considered a “trash tree” and Michael Dirr, author and professor of horticulture at the University of Georgia, has denounced it as “one of the world’s worst trees.”

It has brittle wood and produces prolific amounts of messy litter, including seeds, branches and leaves. It also grows much too big for the average home lot, reaching 50 to 70 feet at maturity.

In addition to the nuisance elm seed bugs, elm leaf beetles can be a problem. Some years, elm leaf beetles cause significant leaf damage and defoliation when their population explodes. Plus, Siberian elm is prone to infection by the bacterial disease called “slime flux.” This infection causes an unsightly and smelly liquid oozing out of the tree.

If your elm is the undesirable Siberian elm and it is not a critical part of your landscape, you may want to consider removing it.

Mature Siberian elms are massive and removal can be expensive, but so is the alternative of spraying the crown of the tree every year to kill the young nymph seed bugs before they have a chance to mature and become a nuisance mid-summer.

Because of the tree’s large size, spray applications to control the bugs should be done by a licensed control operator with the proper equipment.

The bad news is that the elm seed bug was first found in the U.S. in 2012 in Idaho and it has already become a nuisance pest in parts of Idaho, Utah, Oregon and Washington. The worst news is that it is most likely here to stay and will continue to annoy us.

For more detailed information on the Elm Seed bug go to: http://extension.oregonstate.edu/malheur/sites/default/files/spring_2013_esb_fact_sheet.pdf

This story was originally published August 5, 2017 at 6:47 PM with the headline "Garden Tips: Elm Seed bugs annoy us — again."