By Ken Kukorowski
As we hopefully approach the end of “coat season” across much of the country, the pests Mother Nature has so generously provided will be emerging soon to greet us. An awareness of the impact that harsh, cold winter weather may have had on key turf and ornamental insect pests will help you develop a solid, proactive game plan for spring and summer treatments. In addition, as you again prepare to face off against key pests like fire ants and white grubs, the strategies and in-depth insights on these problem pests will help arm you with the tools for a successful, pest-free season.
Surviving the polar vortex?
Turfgrass managers will need to monitor for pests this year as per usual, and if preventive or curative insecticide applications are typical for your region, expect to make them about the same time this year as you have in previous years.
Some reports circulated in January through a [ital>Chicago Tribune<ITAL] w:st="on" Midwest. However, although extreme cold weather (-20 to -30°F) can limit the overwintering of many insect pests, it is important to note that the EAB may not be severely affected since the pest originates from a region near Manchuria, China, where extreme cold conditions are commonly observed each winter.
Another report from Virginia Tech shows that an exotic new pest, the brown marmorated stink bug (BMSB), may not survive the winter very well this year, again due to the polar vortex. It’s possible that initial populations of BMSB may be lower this spring; however, the BMSB may increase in numbers throughout the spring and summer. As late summer/early fall approaches, populations may be at levels requiring treatment, which just so happens to be the recommended time of the year for an insecticide application.
But what about the turf pests such as fire ants, white grubs, annual bluegrass weevil, billbugs, and chinch bugs that have to be controlled annually? It is strongly recommend that you continue to scout or monitor for these pests because the winter should not have had any major impact on their survival or emergence.
Don’t fool around with fire ants
Fire ants infest more than 325 million acres across the southern portion of the United States and pose a serious and growing public health threat, injuring more than 20 million people each year with their stings. Colonies of fire ants can grow to comprise up to 500,000 members. Just one colony can have multiple queens capable of laying 1,500 eggs each, per day.
The fire ant mound is the nursery chamber for the colony. The queen(s) is moved up and down the area beneath the mound depending on the temperature (if it’s cold, the nurse ants move queens down to protect from freezing conditions). Queens and fire ant brood can be moved anywhere from ground level to 6 feet below ground level. Furthermore, fire ant tunnels can burrow much deeper to seek out a source of moisture. Once fire ants are established in your area, cold weather has little impact on the fire ant colony — if necessary, the colony can burrow deep into the soil. Applications of fipronil (Topchoice) beginning now will provide up to a full year of fire ant control.
Strategies for a grub-free season
The most frustrating pest we encounter across the country is the white grub. The Midwest and Northeast suffer most severely from consistent grub problems despite the regions’ cold and often frigid winters. It is expected that white grubs will survive and overwinter this year, and adults will be flying and mating during their normal timing in mid-summer (approx. June-August). Research has clearly demonstrated that white grub survival is dependent on the female beetle selecting and depositing eggs in lush vigorously growing turf. If you provide your customers with well–groomed, lush turf, you create an ideal environment for the female beetles to deposit their eggs. Since the most widely used insecticides provide four months residual control of grubs, there is no need to apply early. While warmer springs can bring beetle flights slightly earlier than usual, years of university research show that grubs fly and mate during the June-August window. In previous years with very early springs, some applications of preventive grub products went out too early and efficacy was sacrificed late in the season. Use a preventive grub insecticide to protect your turf through the end of mating season in August. Preventive application timings of imidacloprid (Merit) are best made in June and July, based on more than 20 years of research.
If you determine that you have numerous overwintering white grubs in the spring, you can remove them with a single application of a curative product like trichlorfon (Dylox). In the fall, if you have white grubs in an area that did not receive proper preventive grub control, you can also use trichlorfon to rescue the area from grubs before predators such as raccoons and skunks tear up the turf to feed on the grubs.
It’s a good practice to keep your preventive and curative grub control options clearly differentiated.
Preventive grub control (imidacloprid). Apply in late May through early August. Provides up to 4 months residual grub control (plus other pests).
Curative grub control (trichlorfon). Apply in spring or fall when grubs are present in turf. Provides almost immediate curative control (after being watered in) of all grubs present, but no residual control.
Trichlorfon should not be used at the same time that imidacloprid is applied for preventive grub control. There are at least nine different species of white grubs that occur throughout the United States, with many or all species occurring in the same location. The timing for the emergence, flying, mating and egg laying for each species is different. If you apply trichlorfon on July 10, for example, you will control the grubs present with this single treatment; however, Japanese beetle females can live for 8 weeks, mate multiple times and have multiple clutches of eggs. Eggs deposited after a trichlorfon application will not be controlled. Therefore, use trichlorfon when all the adult beetles are gone (fall and spring) and the only life stage present is grubs. That single application, at the correct timing, controls the grubs where the application is made. Preventive grub control treatments using imidacloprid provide residual control of grubs, so if some eggs are deposited July 10, they are controlled, and if another species deposits their eggs 10 days later, they too are controlled. These are two very different control strategies for two very different products used to control grubs.
Yes, the polar vortex was very cold. Yes, Minnesota might thaw out sometime in mid-June this year. But don’t sell your sprayers on e-bay or at the local garage sale: the insects will be back this year!
Ken Kukorowski is senior research scientist specializing in Insecticides. He previously led the Bayer Advanced division’s Product Innovation Group. Prior to joining Bayer, Ken accumulated more than 20 years of industry experience specializing in R&D and technical development, with a focus on insecticides. He earned a Bachelor of Science degree and a Master of Science degree in Entomology from Michigan State University; and he earned a Ph.D. in Entomology from the University of Wisconsin-Madison.
Bayer, the Bayer Cross, Topchoice, Merit and Dylox are registered trademarks of Bayer. Always read and follow label instructions. For additional information, visit www.BayerCropScience.us.