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Issue link: https://read.dmtmag.com/i/182361
Landscape and Turf Maintenance Dealing with Grubs: Latest Recommendations E Schroder: How will turf managers first recognize they have a grub problem? Dr. Shetlar: Most professional managers will notice that the turf under their care is not performing well or is showing signs of drought stress at times when soil moistures are okay. However, inexperienced managers miss grub populations until birds or digging animals "show" where the grubs are. Unfortunately, by this time, the grubs are often third instars and pretty difficult to control with inexpensive products. At this time, one may have to use Dylox or Arena and ensure that immediate irrigation follows the application. Dr. McGraw: Probably more often than not, most turf managers recognize they have a problem once they have some serious damage signs. Vertebrates like skunks poking around, raccoons rolling back the turf, or birds pecking at the turf are all good signs of grub activity. This is more likely to be late in the fall and when grubs are fairly large and capable of causing some damage on their own (i.e., feeding on the roots of the plant). Astute turf managers would probably cue into a general wilty or yellowing appearance to the turf in earlier in the fall, 16 Landscape and Irrigation October 2013 and follow this observation up with some sort of soil probing (taking a golf course cup cutter to a section of turf and looking for the actual culprits is, in my opinion, an easy way to confirm grub presence). Masked chafer third instar grub under microscope. Schroder: What steps do you recommend to eradicate the problem? Masked chafer third instar grub in the field. Dr. McGraw: Preventive insecticides are still the number-one go-to method of control. When neonicotinoids like imidacloprid (Merit) came on the market, it revolutionized how we treat for grubs. Before, turf managers had to apply harsher chemicals curatively or after the infestation had been realized. With products like imidacloprid and newer classes like the anthranilic diamides (Acelepryn), applying preventively before egg hatch leads to greater levels of control, since you are delivering a toxin to a much smaller insect (first instar larva vs. a third instar). That being said, eradication is not really possible even with chemical controls. Adult beetles are capable of traveling great distances to find adequately watered soils to lay their eggs in. Even with great control in year 1, some adult beetles will wander in year 2 from neighboring sites. Dr. Shetlar: Late-season grub issues fall into what I call "rescue treatments." This is an extreme form of curative treatment because the large grubs can be 30 to 40 times the body weight of the grub that hatched out of the egg. Another issue is that the grubs often stop feeding once they have achieved their maximum size for the season. I often talk to Dan Potter in Kentucky in September, and he points out that his Japanese beetle and masked chafer grubs have turned a yellow-white Photos courtesy of Dr. David Shetlar, Ohio State University. ric Schroder, editor of SportsTurf magazine, sister publication of Landscape and Irrigation, recently asked two noted academicians, Dr. David Shetlar, professor of entomology at Ohio State University, and Dr. Benjamin McGraw, associate professor, golf and plant sciences at the State University of New YorkDelhi, to update us on treating grub problems. www.landscapeirrigation.com