August 2017

SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.

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www.spor 26 // August 2017 amount that a shrub grows following a trimming event. The growth of treated shrubs is typically reduced 30 to 70 percent, and holds them for 8 to 12 weeks at a time (sometimes longer, depending on the species). This is benefi cial to the property managers as PGRs allow you to focus labor toward the project areas most visible to the client rather than allocating them toward tasks such as maintaining a perimeter hedge or trimming parking lot shrubs. Beyond the operation advantages PGRs provide, there are health benefi ts to the plant as well. First, just reducing the number of prun- ing events a shrub is subjected to has positives from a health stand- point. Pruning puts a plant into a growth "mindset," meaning it is focusing its energy toward growth, often at the expense of allocating energy towards things such as root growth, defense compounds, or storage compounds. Second, modern plant growth regulators, such as paclobutrazol, help stimulate a plant into allocating growth away from vegetative growth and into these other categories such as root growth or defense compounds, making them more resistance to certain abiotic and biotic health threats. There is also research sug- gesting treated shrubs are more resistant to acute drought than untreated plants due to thicker leaves, increased root systems, and higher levels of absicic acid. This plant hormone is know as the "stress hormone," and allows plants to quickly open and close their leaf stomata throughout the day in hot and dry conditions. Thus they can better balance the need to have them open to get carbon diox- ide for photosynthesis with the detriment of having them open and losing water. Application methods and timing Whether we are talking about insects and disease, abiotic is- sues, or growth control, even- tually the discussion needs to come around to applications. Shrubs have some unique chal- lenges for application techniques that are not shared by other living things in the landscape, such as turf and trees. Applica- tions of healthcare treatments in trees can be done a few different ways, including spray applica- tions, trunk injections, and appli- cations made to the soil at the base of the tree. Applications to turf can be made by spray appli- cation or by spreading granular products. Shrubs, however, are generally too small for trunk injection to be feasible and soil treatments have their challenges as well. Ide- ally, soil applications (both granular and liquid formulations) should be made to the mineral soil, but shrubs in the landscape have mulch, dec- orative stones, weed barrier fabrics or, more commonly, a combination of these products covering the soil beneath them. Not removing these barriers prior to application can result in uneven uptake and a further delay in effi cacy of the treatments. Timing of soil applications is also an issue in shrub care, as there is a lag between the treatment date and when you can expect to have effi cacy of the product. Depending on the treatment being utilized, that lag can be anywhere from a few days to a matter of months. Combing this uncertainty with the diffi culty of properly dosing treatments for shrubs, the vast majority of shrub healthcare treatments are performed by spray applications. Spray treatments eliminate the soil cover issues, they have fast effi cacy, and they are fairly foolproof in terms of dosing accuracy. Spraying has fallen out of favor in arboriculture of late, as drift issues make scheduling and Cosmetic issues are serious health issues for shrubs.

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