Golf Course Management

OCT 2017

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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64 GOLF COURSE MANAGEMENT 10.17 Using a soap flush can bring pests to the surface of the turfgrass thatch during the scouting process. Shown here is a European crane fly larva. Photo by Andy Gilroy The best way to make an insecticide treat- ment work its hardest for you is to target the most susceptible stage of the insect. For exam - ple, Japanese beetle grubs generally hatch in mid- to late summer and are small and very susceptible to many white grub insecticides. Applications that target this timing are much more effective than those focused on the late- instar larvae, which are nearly mature and have cut back on feeding because pupation to an adult is imminent. Bluegrass billbugs provide another exam - ple of the importance of application timing. Although billbug larvae do not damage turf early in the year, the adults emerge early in spring, mate and lay their eggs. After those eggs hatch in early to midsummer, the lar - vae burrow into the stems and crown of the plant. Once inside the plant, the insects are protected and won't be visible or reachable with an insecticide, so control becomes quite difficult. Preventive treatments that protect plants from larval feeding early in spring, be - fore egg hatch, are thus crucial for effective control. Understanding such key timing de - tails will make a significant difference in the level of control received from an insecticide application. To treat or not to treat Many times, discovering the actual pres - ence of a damaging insect while scouting isn't a green light for action beyond cultural prac - tices to enhance the health of the turf. One mole cricket adult on a golf course fairway is likely tolerable, but one mole cricket adult on a small par-3 putting green is not. Damage thresholds are typically a general rule based on the degree of damage that is ac - ceptable before other actions need to be taken. That being said, action thresholds will vary widely from one course to another, and even locations within a course will be weighted dif - ferently. The level of tolerance or threshold levels for each area of the golf course will play a major role in determining what actions, if any, should be carried out under an insect con - trol program. Let's imagine for a moment that we've been monitoring and scouting for southern chinch bugs in St. Augustinegrass for the last few weeks. Up to this point, visual observations and flotation sampling (a method of using water to float the insect to the surface using a cylindrical, open-ended container pushed into the soil) have yielded no hits. However, today's sampling floated small red and older nymphs to the surface in significant numbers. Now what? A treatment is warranted, but which product is the best? A well-thought-out program will help eliminate those types of panic questions by taking into account such scenarios ahead of time, so that after a threshold has been ex - ceeded and the decision is made to treat, that action can occur immediately. To reach this point, however, it's imperative to understand what differences exist among products that might be labeled for the same pest (some pyre- throids are labeled for grub control even though they bind tightly to the soil and rarely reach the grubs to impart control), and, more specifically, how they do or do not move in the plant. Insecticides that are absorbed into plant tissues and then move within the vascular system of the plant are generally referred to as systemic. This mode of activity is important for root-feeding, soil-dwelling pests as well as for those that feed inside the stems and crown of the plant, because the insecticide can pro - tect from the inside out. Systemic products typically require a period of time to be ab - sorbed into the plant and therefore perform well as preventive applications before pest ac - tivity is present. They also tend to have ex- tended residual control that may last as long as several months. The opposite of systemic activity is con - tact activity. This group of products does not typically penetrate the plant tissue and stays on the surface, where the insect is exposed to the active ingredient. Contacts are effective for protecting the outside surface of the plant, either as a preventive barrier or, in some cases, after aboveground plant feeding has already begun. Contact insecticides tend to have a quicker mode of activity on the target insect, but also have shorter residual compared with systemic insecticides. These simple delineations can assist turf - grass managers in choosing the correct prod- uct for the scenario in question. In the case of the chinch bug situation described above, a contact such as a pyrethroid (lambda- cyhalothrin, bifenthrin, etc.) was the product of choice, because the population was small and sensitive to pyrethroids (more on resis - tance later), and a spot treatment of the local- ized area was all that was necessary to stop the bugs from becoming a large-scale problem. Spot treatments can be effective at times, but preventive applications of systemic insecti - cides such as neonicotinoids (thiamethoxam, imidacloprid, etc.) or diamides (chlorantra - niliprole, cyantraniliprole, etc.) to areas with Growing degree day tools GreenCast (Syngenta): www.greencastonline.com/ growing-degree-days Michigan State University GDD Tracker: www.gddtracker.net Ohio State University: www.oardc.ohio-state.edu/gdd Oregon State University: www.uspest.org/cgi-bin/usmapmaker.pl University of Massachusetts Amherst: www.ag.umass.edu/landscape/ fact-sheets/growing-degree-days- for-management-of-insect-pests- in-landscape University of Nebraska-Lincoln: http://turf.unl.edu/turf-advice

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