Golfdom, March 2014

Super Science FIGURE 3 The characteristic dollar spot lesion bleached white leaf blades with brown borders Continued from page 27 not have the exact same mode of action as in other classes and from a practical perspective includes compounds with widely varying efficacy Boscalid Emerald and flutolanil Prostar are in the SDHI class Of course Prostar is not a new fungicide nor is it the least bit effective against dollar spot Emerald is both relatively new and primarily targeted to control dollar spot New SDHI compounds include penthiopyrad Velista Syngenta and fluxapyroxad Xzemplar BASF All research reports to date support very good to excellent efficacy of these fungicides against dollar spot but results are mixed with regard to control of other diseases Again they are site specific FRAC Code 7 penetrant compounds and antiresistance tactics should be considered when positioning SDHI applications in the season long fungicide program APPROACHES TO UTILIZING FUNGICIDES EFFECTIVELY Given these effective tools to stop pathogen growth and allow turf recovery to proceed how has this simple pathogen morphed into such a relentless problem Consider that infection and colonization occur over a broad temperature range Therefore dollar spot outbreaks are a threat for most of the growing season and superintendents must be constantly vigilant of conditions that promote infection Depending on expectations season long protection against outbreaks is warranted We have an impressive array of fungicides to do the job but regulatory restrictions and the threat of fungicide resistance present a serious challenge to superintendents as they formulate an effective approach to dollar spot control The program approach is the de facto preventative approach It is my opinion that this approach will result in the most effective and efficient use of our chemical assets for disease control If you are skeptical consider the tried and true axiom an ounce of prevention is worth a pound of cure I understand the argument for the curative approach We have very effective fungicides that stop pathogen growth in turf they are chemotherapeutic However because pathogens are microscopic with one dollar spot infection center containing tens of thousands of infectious cells and the infection process including an incubation period there is so much more disease than meets the eye As a result the pathogen component of disease pressure is increased Over a given season depending on the weather more fungicide will be required for adequate control under conditions of high disease pressure than low disease pressure There are countless reports of season long efforts to catch up after a dollar spot outbreak has occurred Results are not always satisfactory and unless cool dry weather lends a helping hand it will always be more expensive than the preventative approach This may also hasten the evolution of fungicideresistant pathogen populations Non chemical control options cannot stand alone in controlling dollar spot when weather conditions favor infection However they do serve to reduce disease pressure and therefore may be exploited to improve the efficacy and efficiency of any chemical control program Some modern creeping bentgrass cultivars Declaration and others possess a genetic resistance to infection They are not immune to dollar spot but compared to more susceptible creeping bentgrass cultivars e g Penncross Pennlinks L 93 disease develops more slowly and infection centers are often smaller in size As a result of the improved genetic resistance less fungicide will be required to achieve acceptable levels of control than on the more susceptible cultivars Certain cultural practices such as maintaining turf with ample nitrogen nutrition displacing morning dew by poling or mowing and implementing a lightweight rolling regimen also reduce disease pressure and contribute to optimal use of fungicides 28 Golfdom March 2014 Golfdom com PHOTO BY RICK LATIN