How To: Map pest infestations
Efficiency and effectiveness is important in any business, including turf management operations. When you think of pest management in turf, you know that these principles are true for several reasons. First, you want to avoid unnecessary and unsightly turf injury. You also want to do so in a cost-effective manner. Additionally, you want to obtain a high level of control with minimal risk to the environment.
There are many components to effective pest management, including selection and use of an appropriate pesticide. Proper selection requires proper identification of the pest problem. This is a paramount first step. There are instances where you might make an assumption based on past experience or damage symptoms as to the cause of the turf injury. Sometimes these assumptions can be wrong. Finding and properly identifying the pest is one key component that you must never overlook.
The development of a reasonable understanding of pest biology is also essential, and it's not as much trouble as it might seem. Most turf areas only suffer from a few insect pests in a given year. In most situations, it's the same two or three every year. Therefore, gaining a good working knowledge about the insects that cause you problems won't require reading and memorizing lots of reference material.
Acquiring the appropriate knowledge about certain pests does several things. First, it helps you understand your enemy. In any battle, your chances of success are much greater if you understand your enemy's strengths and weaknesses. A significant portion of this is an understanding of the insect's life cycle. Knowledge about an insect's life cycle is important for several reasons.
First, it helps if you know when to expect the pest problem. If the insect has several generations each year, then it helps if you understand that the pest attack may occur repeatedly on an annual basis.
I have encountered situations where turf managers apply successive controls for an insect pest that has just one generation each year and mistakes are made. The thought behind this was that they wanted to prevent any more problems in that location. But if you treat the problem effectively the first time, knowing the pest has just one generation per year tells you that a subsequent application is wasted.
Another confusing situation may occur when a turf manager treats for a pest and then, several weeks later, finds insects in the area they just treated. Typically, they'll come to one of three conclusions: (1) the product did not work; (2) the area was reinfested from surrounding areas; or (3) another generation hatched/emerged. If you know the pest has one generation per year, you know that option 3 is not possible, and this should prompt you to look more closely at 1 and 2.
In recent years, understanding pest biology has become even more important. Many of our newer insecticides work most effectively when targeted against specific life stages of the insect. The new products for white grubs, such as Merit (imidacloprid), Mach 2 (halofenozide) and the anticipated Meridian (thiamethoxam), make accurate timing critical. While these products may provide some control against larger grubs, they are going to be most effective when applied at egg hatch to work against the newly hatched, small grubs.
Many turf managers like these newer products because they have a better environmental profile as compared to some of the older products, and are quite effective. But applying a product against a very small insect that has yet to produce any symptoms of turf injury can be tricky, and challenges traditional notions of IPM.
Obviously, knowledge of pest biology and life cycles is critical. For example, if Japanese beetle grubs are a consistent problem, and you understand that these grubs are immature stages of adult Japanese beetles, you are headed in the right direction. If you know that Japanese beetles have but a single generation each year, you are even further along in targeting your application appropriately. Finally, if you understand that when you see Japanese beetles defoliating various ornamentals it means the time for mating and egg laying is rapidly approaching, you are well on your way to effectively controlling the grubs. In effect, it means the time to apply the previously mentioned products is near.
This example is an easy one to follow because Japanese beetles are so obvious when they are present. Other species of white grubs may have adult beetle stages that are much less conspicuous, such as Oriental beetles. In these situations an indication of the timing of egg laying is not as obvious. Forecast models often based on degree-days or plant development are available for a few pests and can be developed for specific sites. While the development patterns of specific pests may vary somewhat, most are fairly consistent from year to year. There may be a little variation, but if you know the approximate life cycle and timing of egg laying, a good job of management is possible. The residual activity of the new grub products is sufficient to give you a little margin of error.
Once you've addressed the timing issue, you must move on to another important matter: Where will insect problems occur? Insects are similar to people in that they have a habit of showing up most often in the most attractive surroundings possible. Unfortunately, we often make a mental note of pest occurrences only to forget that we've seen the same problem in the same place several times before. Mapping and record keeping can help you spot the “when” and “where” of infestation patterns.
Mapping and record-keeping (of pest occurrence) is important for many reasons. It can save you time and money. Good mapping helps you target your scouting efforts as you look for pests. You know where to look first. It also helps you apply pesticides wisely. You only apply them where they are needed. This has obvious economic and environmental benefits. It is particularly important when treating with certain products for white grubs or mole crickets. These products are applied before symptoms are present and, unless you want to treat every square foot, good record keeping of past infestations is critical.
Another equally important benefit is that once you begin mapping, you can begin to look for patterns. Are there any consistent features among sites that regularly suffer from pest attack? In the case of insects, are the areas that get attacked typically wetter or drier? Do they have northern or southern exposure, too much thatch, cutting height, etc.? When mapping reveals consistencies, then you can begin to think about proactive cultural practices that may lessen the likelihood of pest attack.
How do you map pest problems? The quick and easy answer is that you put down on paper what you've got in your head. This gets easier all the time with the various hand-held devices and software on laptops to make electronic mental notes. Develop an electronic or hard copy of all the sites. Record pest occurrence on these “maps” and begin to develop a database through time. The real value of mapping is its value as an archived reference source.
Integrate scouting information into the maps. Where the pests aren't is just as important as where they are. If you preventively treat for certain pests, continue to scout for pests outside the treated area to record the accuracy of your targeting.
Depending on your time, staff, budget and the type of service you offer, all scouting information can be placed on maps. This not only serves as a reference for where pests occur, but also as a source of information as to the timing of pest occurrence. Timing can vary dramatically on a northern to a southern slope. This is most clearly seen when represented graphically as part of a mapping plan.
Maps can be simple or sophisticated. They can be hand-drawn on paper or imbedded in a GIS/GPS program. The key is scouting to obtain the information and recording it in a format you and your staff can understand. It is also important to include details. Something specific you remember now may be forgotten in a year or two. Also be sure to use permanent landmarks for mapping infestations. Some landmarks have a habit of disappearing through time.
The final step is using the maps. Keep them up-to-date and refer to them often. Look for trends, reminders as to the timing of certain problems and ways to modify the environment to reduce infestations. You also should use your maps as a tool to monitor the success of your management programs.
Dr. Rick L. Brandenburg is professor and extension turfgrass entomologist at North Carolina State University (Raleigh, N.C.).
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