Readers sent us their turf pest management questions, and we posed the most frequently asked questions (FAQs) to a couple of industry experts — Barry Troutman, Ph.D., National Association of Landscape Professionals Technical Advisor; and Benjamin McGraw, Ph.D., Pennsylvania State University Associate Professor, Turfgrass Science. Their feedback is as follows:
FAQ: What recommendations do you have for managing pesticides in rotation to reduce the possibility of resistance being built up in the pest to certain chemicals?
Troutman: Rotation of pesticide modes of action is important, particularly on insects that have multiple generations in one season. We are currently limited to only a few mode of action alternatives. The most frequently used are pyrethoids and neonicotinoids, which have replaced the much more toxic organo-phosphates and carbamate insecticides.
McGraw: Pesticide resistance is not a major concern for the vast majority of product plus insect combinations in sports turf. The two species of insects where insecticide resistance is an issue are either golf course (annual bluegrass weevil) or home lawn (southern chinch bug on St. Augustine grass) problems. So, not a huge concern with the insects we have, given the products used and the number of generations per year. That is not to say that it will never be an issue.
FAQ: Do insects have a turf species preference? If so, what insects prefer what grass species?
Troutman: Insects are absolutely preferential feeders, and insect problems also vary by geography. There are nearly a dozen different species of white grubs each with slightly different life cycles that feed on root systems of turfgrasses. The southern chinchbug feeds on St. Augustine but not on other turf species, while the northern chinchbug feeds only on Bluegrasses. Tropical sod webworm is really particular, it will eat crabgrass first, then move to Bermudagrass before eating St. Augustine or Bahiagrass. The interactions are extremely complex and knowing them is what makes us professionals.
McGraw: That is a pretty big and general question. Some sports turf insects may have a narrow diet (e.g. Black turfgrass ataenius might be found in Poa annua patches in an outfield), whereas others do not care about species as much as they would site conditions (e.g. irrigated turf vs. droughty turf). To speak generally, the major insect pest issues on sports turf (white grubs, mole crickets) are likely to be generalists and not be too finicky on which turf they feed.
FAQ: What tips do you have regarding application timing? What is too early? What is too late?
Troutman: Timing is critical for most applications to control pests. Weeds are easiest to control in the seedling stage. Often it easier to prevent problems by controlling overwinter adult insects before they breed in early summer. With caterpillars, in most cases control must be delayed until the problem occurs. Research and recommendations from land grant universities are the best guide for control timing in each region of the country and professionals watch them closely.
McGraw: That all depends on what you are finding by actively scouting the turf. Sampling is required to answer that question.
FAQ: What impact would neonicotinoid bans on pesticides have on the ability to control insects?
Troutman: Banning of neonicotinoids would create potentially huge control problems. It would eliminate one of landscape and agriculture’s most critical resistant management alternatives. In an urban environment, neonic’s are the only effective control for tree-killing pests like the emerald ash borer. They are much less toxic than other products used to control white grubs.
McGraw: The potential ban of neonicotinoids would have a major impact on a sports turf manager’s operation. White grubs are likely to be the major insect pest that they are dealing with (independent of region within North America). That being said, white grubs have been, and continue to be, effectively managed with one insecticide application per year. Between the 1990s and today, neonicotinoids have been the number one product for that control. Since these products have been around since the 1990s, many active ingredients are “off-patent,” allowing generics to enter the market and reduce the cost of an application. Although there are newer products on the market (e.g. anthranilic diamides like Acelepryn), the neonicotinoids remain much cheaper. A ban of neonicotinoids would cause the cost of controls to increase dramatically.
FAQ: Is the current pollinator issue and “bee-friendly” movement legitimate?
Troutman: Bee populations are indeed threatened, but it’s not just about insecticide use. The honeybee is intensively managed and stressed by a lot of travel from crop to crop. It is a fairly “inbred” species, so it is susceptible to a lot of pests — the most important is the varroa mite. These factors are often overlooked by those interested in banning pesticides. The turf use of insect controls is a very small part of the problem since turfgrasses and most landscape plants are not bee pollinated. The greatest risk to honeybees occurs in agricultural areas where bees and insect control are both critical to crop and food production.
McGraw: Concerns over pollinator health are legitimate. Insecticides affect insects, and we have to be aware that our turfgrass insecticide applications may have unintended consequences. Part of that is understanding how pollinators may be harmed, and what can be done to minimize any potential risks. There has been a great deal of work from Dr. Dan Potter’s lab (University of Kentucky) showing that the risk can be minimized with the proper selection of products, choosing different formulations (granules vs. liquids), and how we take care of the product after application. It’s not rocket science. So, yes the concern is legitimate, but the risks may be minimal (if not negligible) with the right application procedures.
FAQ: With stricter pesticide restrictions, what are some of the non-chemical means of control (or alternative insecticides or management practices) that can be used?
Troutman: Most products designed to control insects will also control honeybees if misapplied. Even so called non-chemical controls will kill bees if improperly used. The best course of action is to avoid treating plants in flower with any control product. With lawns the best practice may be as simple as mowing the flowering weeds before making an application of insect control or too use a granular product that will not damage bees. EPA has added bee protection language instructions to all control products that threaten bees. Following these instructions is the most effective way to protect bees and our urban environment.
McGraw: I was just in Ireland and Scotland and witnessed what the loss of neonicotinoids could look like. They do not have the option to use anthranilic diamides and have, more often than not, resorted to not taking action. The only other option that I presently see is the use of entomopathogenic or insect parasitic nematodes. The cost of using EPNs is high, though may come down if more people adopt the technology. There is quite a lot that goes into the proper use of EPNs, since they are living organisms and need to be handled with care.
FAQ: What do you believe to be the biggest issue in terms of insecticide misuse that, if resolved, would help place turf insecticide use in better light?
Troutman: Not all bugs are bad bugs, and healthy landscapes can tolerate low populations of damaging pests, so be certain that treatment is necessary and then read and follow label instructions. Just as important is to create and protect pollinator habitat. Pollinator gardens attract and feed butterflies, solitary bees and even hummingbirds. Like turfgrass, they have important environmental functions with the added bonus of being downright beautiful.
McGraw: I would say that the biggest misuse is improper timing of application or making an application to when a pest is not present. Both issues can be avoided with a little scouting. It is a pretty simple thing to do, but many don’t take the extra step to do the work that is involved with scouting for insect pests. I think that the effectiveness and the lengthy residual control of some of our insecticides has made some lazy when it comes to monitoring for insects.
Above photo by David J. Shetlar, Ph.D., The Ohio State University