Hanging On Strong And Popping Up Again

By John H. Foy, director, Florida Region
May 28, 2013

A classic example of witches broom damage caused by bermudagrass mites.

While winter overseeding of bermudagrass putting greens, tees and fairways at courses throughout Florida has declined over the past several years, it is still a practice that is used. Overseeding with cool season turf species such as Poa trivialis and perennial ryegrasses in the mid- to late fall ensures that a green, actively growing turf cover is present during the time when peak seasonal play is being hosted and the base bermuda is in a semi- to fully dormant stage. Yet, with establishment of an overseeding cover, additional competition and stresses are exerted on the base bermudagrass. This in turn increases the potential for areas of weak and thin turf coverage to be exposed and deterioration in the overall quality of overseeded areas during the transition process that occurs in the spring to early summer. As discussed in the webcast, Winter Overseeding Transition Management, employing a proactive program during the spring is recommended to minimize the occurrence of the “transition blues.” However, the weather will always be a controlling factor and to date, weather conditions in Florida have not been conducive to accomplishing a smooth and gradual transition back to a dense and healthy stand of bermudagrass.

Similar to other regions of the country, a cool and prolonged spring has been experienced in Florida during 2013. The combination of daytime temperatures staying in the low to mid-80’s, low relative humidity and timely rainfall has been very favorable to cool-season turf growth. Thus, even in South Florida, it is being found that 40 to 60 percent ryegrass coverage still exists in fairways at the end of May. Typically by this time the transition out of overseeding cover has been completed in South Florida. Along with a moderate to high percentage of the overseeding cover hanging on, temperatures have not been sufficiently hot enough to support resumption of sustained active bermudagrass growth. At a couple of courses recently visited, where chemical transition aid herbicide treatments had been conducted, the base bermuda has been very slow to fill in and this has further added to the challenge of providing acceptable playing and aesthetic characteristics.

To ensure that the base bermuda of overseeded putting greens, tees and fairways is able to fully recover from the cumulative negative impacts of this practice, at least 90 to 100 days without competition is needed. Thus, completing the transition out of the overseeding cover as quickly as possible is critical over the next several weeks using a combination of mechanical and chemical treatments plus adequate fertilization and irrigation to support good bermudagrass growth. A more aggressive proactive management program may not reduce the severity of the transition blues, but will certainly shorten the time that they must be tolerated.

An additional pest concern that has been encountered over the past few weeks is bermudagrass mites. A couple of years ago it was noted that an increased incidence of bermudagrass mite damage was being observed on courses around the region. Typically, mite activity is greater during the late spring to early summer and when hot and dry conditions are prevailing. Mites are very tiny (about 1/130 of an inch long) insects that live under the leaf sheath of bermudagrass. Thus, identification in the field is quite difficult and they are also protected from contact insecticide treatments. Infested areas typically first exhibit a light green to yellow color. This is followed by a shortening of leaves and internodes that results in a tufted or witches broom appearance. Depending on the situation, it is sometimes recommended to mow as low as possible or scalp infested areas, followed by collecting and removing the grass clippings to reduce mite populations. Chemical controls recommended by the University of Florida include bifenthrin, deltamethrin and lambda-cyhalothrin. It is also recommended to include a wetting agent in the tank mix to improve application coverage. Repeat treatments can be necessary. Proper fertilization and irrigation will facilitate recovery from mite damage.

Source: John Foy (jfoy@usga.org)

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