Tips From The Pros

SUMMER STRESSES AND PESTS MANAGEMENT

Summer can be a rough season for turfgrasses, both warm and cool season grasses. Beyond the environmental stresses like chronic heat stress on the cool-season grasses, summer is a time of pests. Be it fungal diseases, insects or weeds, pests love the summer. Not that there aren’t pests all year on turf, but summertime really can bring pest challenges, especially on cool-season turfs.

The mere presence of a turfgrass pest (disease, insects or weeds) is not by itself enough to get the boom sprayer and pesticides going. Many will simply run their course in a few days or weeks. Many will not, and may cause significant damage. The key defense is the turf managers knowledge and experience in basic disease-plant biology. Every situation calls for a differently crafted response. A good concept to keep in mind is what is called the disease triangle, but it can also be employed for weeds and insect pests. The idea is that three things are needed for a pest outbreak: A susceptible host, a viable pathogen or pest, and the right environment. If any of these three things are not present, there is no outbreak. As such, your turfgrass disease management program should work on all three of these conditions and not just focus on the pest or pathogen. Good and appropriate cultural practices like aerification and others can take away the susceptible disease environment. Generally you want to minimize using field covers in the hot summer months, but to prevent rainouts and save the field for the rest of the season, they are a great tool. Use a white side up approach to keep temperatures under the field cover from elevating. Go “under cover” with frequent checks of temperature and other conditions under your field cover in summer months.

Under certain conditions, a field tarp can create a susceptible disease environment. You may consider an appropriate preventative fungicide treatment for periods when you have to cover for extended periods. For longer duration coverings, look for weather windows where you can temporarily remove the field cover for as long as possible and redeploy it before more precipitation comes in. A little light and drying may reduce the susceptibility of the under-cover disease environment.

Insist that any rented flooring used for concerts that come in from a previous venue be washed before being brought onto your field. This may knock down the numbers of disease inoculants and even prevent some exotic turf bits or insects from being planted in your turf.

By using or beginning to convert to turfgrass species and varieties that are resistant to the pests that you will likely encounter in your area, you effectively remove the susceptible host from the disease triangle, as does keeping healthy low-stressed grass.

Good, early pest identification is a product of education and experience. Whenever possible, it is a good idea to get confirmation from a laboratory specializing in plant diagnostics. Call your local county extension agent to get started and find resources. Proper sampling will usually get you some answers within a few days, or even less depending on the lab and how busy they are. Keep a good log and calendar of any and all pest outbreaks and issues on your fields. Many pest outbreaks can be scientifically modeled, narrowing your search for signs and symptoms of turf pest damage. There are even some good apps available as an aid to turfgrass pest ID. While there are several others, I also like TurfPath. In short, educate yourself on your local turfgrass threat theatre and you’ll get one step ahead of most pest problems, making them much easier to manage. Good disease ID relies heavily on signs and symptoms. Simply put, a sign is seeing some physical part of the pathogen like mycelium, spores or other. Early, dewy summer mornings are a good time to inspect your field for signs of mycelium. The challenge with turfgrass disease ID is that these fungal parts can be microscopic. This is where a good plant diagnostics lab can help. If needed, they will culture out some good fungal growth on a Petri dish to confirm signs. A symptom, on the other hand, is an expression of the disease on the turfgrass plant itself in its leaves and roots. Various diseases express themselves with different turfgrass symptoms that can be of great aid in identification.

Cool season turfgrasses are often stressed from prolonged hot weather which can weaken their natural defenses to pests, especially fungal diseases. In managing pests, developing a sound Integrated Pest Management (IPM) system will be your most efficient and environmentally safe approach in my opinion. There are several aspects to a good IPM program (books are written about it) but really only a few concepts-which I focus on here.

A good IPM program focusses first on plant (turfgrass) health and its ability to ward off pest damage. Turf pests are opportunists, jumping on plants weakened for whatever reasons. Turfgrass health starts with a balanced, fertile soil in good physical health. Generally, that means any way you can to practically increase soil oxygen. A soil that won’t drain in the summer heat is a great way to kill off a lot of turf. Many elements, especially nitrogen, have a direct influence on disease susceptibility, so a good turfgrass fertility program is also part of your IPM program. The appropriate use of fertilizers can act as your best herbicide in combating weeds, especially in the lower mowed turfs on athletic fields. Mowed turfs will outcompete most weeds, if given what they need-at least most broadleaf weeds. Annual and perennial grassy weeds, on the other hand, can be very difficult to eradicate or even manage.

Use irrigation judiciously to keep drought stress at bay, which can come on much more quickly under mid summer’s stressful triad of sun angle, day length and high temperatures. Manage the leaf wetness in the turfgrasses as best as practical. Fungal turfgrass diseases, to varying extents, need a moist or wet environment to flourish and propagate. Many are spread over the turf by the splashing of free water in the turfgrass canopy during operations like early morning mowing on a dewy turf. This can’t always be avoided, but anything you can do to avoid splashing free water and achieve at least several hours or more a day of a dry turf canopy will aid in reducing most fungal disease outbreaks in my experience. Again, this is not always possible or practical, but the more you can do to mow dry turf and irrigate late nights when the turf may already be wet from dew and break the leaf wetness cycle during the daytime, the better.

A new approach to disease management in turfgrasses is the potential use of plant elicitors for systemic acquired resistance (SAR) to essentially “vaccinate” the plant by using certain proteins and other chemicals to turn on genes and effectively create a disease resistant plant. Any new plant growth acquires this “turned on” resistance. There are already a few early fungicides and some other products using this technology available and it may become a more widespread way to manage some turfgrass diseases and even insects eventually, lowering the amount of fungicides and insecticides used overall. Mostly in the research stages now, it is a promising technology that turf managers should get more familiar with.

Mow with sharp blades on a well-adjusted and maintained mower! This sounds so simple and obvious, but is too often neglected as the heat sets in on mower crews. The cut leaf blade of a mowed turf is an injury and a good entry point for fungal disease pathogens. A sharp blade makes a clean cut through the tissue that will heal much faster than a dull cut. It’s much like how a paper cut on your finger seems to take much longer to heal than a sharp knife or razor cut does.

Alas, pests happen. But a good IPM program determines in advance what the various economic thresholds for the specific likely pests are. Try as best as possible to quantify this threshold of pest levels and potential damage. For example, how many billbug grubs, on average, per sampling square foot will be the threshold for considering appropriate use of an insecticide? In other words, what level of each potential pest damage can we tolerate before we begin to lose value in the stand of turfgrass and incur costly repairs? Value may be the revenue produced on the field, maybe how many games/practices can be accommodated (Carrying capacity of the field) or more importantly the safety of the field for the athletes that use it. Like any good business person, you have to evaluate your risks accordingly ahead of time. Environmental stewardship in turfgrass management does not mean a ban on the use of safely registered pesticides, rather it is a more overall approach to managing disease and risk. What is a greater risk, a field falling apart with a chafer beetle invasion and having to close for a year because of a pesticide ban or maybe being overtaken by weeds which can make the surface harder to fall on, and attracting more stinging/biting insects that could potentially cause bad reactions, or the safe use of a proven insecticide and closing the field if indicated? Absolutes rarely work in nature.

If a fungicide treatment is indicated under your particular protocols, and in standing with your IPM program, you have to know which ones to use and exactly how to safely and effectively use them. This takes specialized training and education. You may be required to be licensed and/or certified to apply pesticides in your state or community.

A good IPM program uses pesticides after other measures have proven ineffective in lowering pest damages below the economic threshold. Early detection and correct diagnosis/identification of the pest is key, as there is often preventative and curative rates on pesticides-curative rates typically much higher. Using the wrong pesticide for the particular pest is wasteful and ineffective and may be illegal. A good field manager knows exactly what he/she is doing with such products and is qualified to use them. If not, they contract out pesticide applications to a qualified contractor. Always follow all applicable regulations and follow the label instructions on pesticides and any products you may apply to your fields.

Turf Tips 101: Other Pest Management Tips

• Look for birds pecking into your turf. Many birds are very tuned into insects. They may be digging after a turf damaging insect. Even if the birds are not present, you may see small holes left in the turf canopy and thatch they leave from probing for and digging out insects.

• Get a good set of hand lens and maybe a digital microscope. Capture images of your signs and symptoms so that you can send them to others for ID help. Attach any images you have to your pest calendar.
• There may be abiotic causes for what you are seeing in terms of symptoms. Abiotic diseases are not caused by a living pest, unless human. The bleached and shredded leaf tips on a natural grass field mowed with dull blades is an example of an abiotic disease.
• Keep up to date with your education. Pathogens and pests change and so do our turfgrass responses and practices to manage them. There are new pest management technologies always coming out of our fine university and other research programs.
• Many times, the pest you are seeing may be a secondary invasion of your turf after a previous pest has weakened the turf. You may also be seeing symptoms that are being caused by more than one pest at a time. Keep an open mind and see what you are not looking for.
• Have a disease response plan in place well before the outbreaks hit. Know where your best and closest plant diagnostics lab is, and when the sample drop-off hours are. Get others in on your issue. When you call your favorite turfgrass extension specialist at a state land grant university, you should have already established a working relationship with that individual. Have a good image or two on your phone ready to text or email to any number of trusted specialists and trusted colleagues to help you with your identification and management of any pest issues.
• Manage your pesticide inventories carefully. When you finally ID a serious pest outbreak, now is not the time to begin shopping for an appropriate product for control. Chances are good that others have similar issues and inventories at distributors can temporarily run out.

Resources of the Month

Did you know that there is no botanical scientific classification of plants as weeds? If you like a plant, fine. If you don’t like that same plant- it is a weed. Perhaps the best definition of a weed is simply “a plant out of place’

Purdue Extension has a good basic paper here on turfgrass disease ID and management.

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“Agricultural science is largely a race between the emergence of new pests and the emergence of new techniques for their control.” – Aldo Leopold