By Tim Kowols
Landowners will soon be able to assess and treat their damaged lawns as grubs reach their mature form. Beetles like the junebug and European Chafer can cause thinning and dying patches of grass due to their own feeding frenzy, but hungry birds and skunks can dig up the turf in search of their own meal. Door County UW-Extension Agriculture Educator Annie Deutsch says landowners can start preventative maintenance for next year in the next week or two.
Deutsch says European chafer numbers are quite high in the area but hopes the population begins to level off like it has in other states. You can read more of Deutsch’s thoughts on grubs and learn how you treat your grub damage by following this story online.
It’s that ‘grubby’ time of year!
By: Annie Deutsch, Door County UW-Extension Agriculture Agent
Driving through the county, it is clear that there is major turf damage yet again. Many yards, parks, and other grassy areas have patches of thinned out, dying turf or sections where it looks like a rototiller came through.
While grass can die from multiple factors (too much shade, salt from winter roads, too much water, too little water, diseases etc.), the most probable reason for the symptoms we are seeing is due to grubs. But luckily, the period of major grub damage in the spring is coming to a close.
These lawn grubs are most often the immature form of two different beetles: May/June beetles (Junebugs) and the European Chafer. May/June beetles are a group of native beetle species that can cause occasional turf damage, but rarely the extensive damage that we have been seeing the past few years.
European chafer is the beetle species to blame for the damage. As the name suggests, the European chafer is an invasive species from Europe that has been in the United States for around 80 years, but only recently arrived in Wisconsin. This is the reason that you may have never had turf damage before but are seeing it now.
European chafer grubs feed primarily on grass roots resulting in thinned or dead patches of grass. Other animals including birds and skunks feed on the grubs which causes that ‘rototilled’ look.
Luckily, the grubs do not feed all year. In the next couple of weeks (this is an estimate because insect development is temperature dependent), the grubs will pupate (transform) and then emerge as adult beetles. The adult beetles will swarm around trees and outdoor lights, but they rarely feed so they will not cause damage. Therefore, as the grubs begin to pupate, that is the ideal time to reestablish damaged parts of your lawn.
May/June beetle adults tend to emerge a bit earlier than European chafer adults and the May/June beetles are definitely active now. If you notice any brown oval-shaped beetles that are around ¾ of an inch long and often stuck on their back with legs flailing, then those are them! I saw five right outside my front door this morning! European chafer adults look very similar but are smaller (closer to ½ of an inch long) and a slightly lighter color.
For recommendations about determining whether you have grub damage and ways to treat for them, visit our website for a number of articles addressing those topics: http://door.uwex.edu/horticulture or contact our plant help desk at 920-746-5984 or firstname.lastname@example.org.
Unfortunately, as with many invasive pests, even the best attempts at controlling this insect may not have complete success. European chafer numbers are quite high right now and will likely remain so for the near future. There is evidence in some states that populations leveled out over time, so hopefully that will be true here as well. Perhaps rather than focusing on the damage, use this as an excellent opportunity to learn more about entomology and insect life cycles!