Avoiding Product Failure Due to Resistance
As a lawn care provider, you have many tools in your arsenal to get the job done. What if some of these tools were taken away? The job could become more difficult, expensive, or labor intensive. Pesticides are tools we use at times to provide the best landscapes possible. While providing the plant with optimum fertility and growing conditions is the best defense against pests in the landscape, various chemicals are needed in many circumstances to meet homeowner expectations. Responsible use of these chemicals includes following the labeled rates and application methods, proper scouting of the pest, and rotating modes of action periodically for resistance-susceptible pests.
Target pests develop resistance through chromosomal changes over time. Repeated applications of the same or similar chemistries expedite pesticide resistance. Organisms that reproduce quickly are more susceptible. For example, let’s say an insect routinely has 100 offspring in their life cycle, and your insecticide kills 98 of those, with two of them carrying resistant genes and tendencies. Those two surviving insects will each have 100 of their own offspring, which will carry on the parent’s DNA that very likely may have been modified to fight off the effects of a particular insecticide treatment. In this example, the next generation may each have 100 offspring of their own, creating a population of resistant pests. Click here to find a helpful visual of this process.
Chemistries are classified into different modes of action. Fungicides are classified into FRAC groups. Insecticides use IRAC classification, and herbicides use Mode of Action or WSSA classification. Pesticide labels typically have their mode of action classification found predominantly on the first page, in bold font that is easy to spot. Use this as a quick reference to determine appropriate rotational applications. Three groups that should be a focus can be found below.
Herbicide resistance has become an issue in agricultural production, as well as in golf turf. Poa annua (annual bluegrass) and goosegrass, among others, have shown herbicide resistance in turfgrass settings. While we haven’t had many issues in lawn care specifically, irresponsible use of herbicide and not rotating chemistries could lead to resistance in other commonly found weeds.
Fungal pathogens are highly susceptible to resistance. In lawn care, we are limited in chemistries that are labeled for our use. Most commonly, DMI and QoI (FRAC groups 3 and 11, respectively) chemistries are used, many times in conjunction for added activity. Examples include Pillar SC, Zoxy-PG, and Armada 50 WDG. These products provide ideal protection and curative properties that last up to 28 days. For multiple fungicide applications made in one season, consider using a product like Xzemplar (FRAC group 7) in your rotation to avoid resistance. Using the same mode of action two or three times consecutively often opens the door for resistant populations that lead to a wasted application, wasted money and time, and disappointed customers.
Spider Mites are very susceptible to resistance. It is important to utilize multiple modes of action within this group, as consecutive applications of the same chemistry will produce resistance. Rotate each application to a different mode of action each and every time. This is critical for those who make multiple applications per growing season. TetraSan is a great rotational miticide that has ovicidal properties to kill spider mite eggs.
Chemicals are not inexpensive. Utilize them responsibly to make sure they work as designed. The staff at Advanced Turf is here to help identify rotational chemistries to ensure your chemical applications give you the most bang for your buck.