SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/147380
FieldScience Dealing with grubs: latest recommendations Editor's note: We asked two noted academicians, Dr. David Shetlar, professor of entomology at Ohio State, and Dr. Benjamin McGraw, associate professor, golf & plant sciences at the State University of New York-Delhi, to update us on treating grub problems: SportsTurf: 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 the 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 then 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, 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 a easy way to confirm grub presence). Given the workload of sports turf managers, especially those that have many schedule games and activities on fields in late summer to early fall, proactively sampling large areas with a cup cutter is probably not feasible. Restrict- ing sampling to where grubs have been a problem in the past and in high-valued areas is a more realistic approach. ST: What steps do you recommend to eradicate the problem? 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 applied 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 (1st instar larva vs. a 3rd instar). That being said, eradication is not really possible even with chemical controls. Adult beetles are capable of travelling great distances to find your 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 color which in- I think that, especially on sports fields, we can minimize the effects of white grub damage substantially by developing a healthy turf stand — Dr. McGraw 30 SportsTurf | August 2013 www.sportsturfonline.com