One of the great things about this industry is that everyone is always looking out for their peers. I found this bulletin pretty interesting from Bayer’s Green Solution Team. A group that has come together to send out helpful tips and turf management advice to help managers through the difficult seasons.
The bulletin below will help explain some of our thoughts and reasons behind increased chemical applications in these weather patterns.
Green Solutions Team
Reasons for Increasing Fungicide Rates and Reducing Spray Intervals in Summer Weather
By Zac Reicher and Paul Giordano, Ph.D.’s
Summer weather is here with regular thunderstorms, torrential rains in some areas, high humidity and temperatures pushing triple digits. For most effective control of diseases, it’s time to increase fungicide rates and/or reduce spray intervals.  Here is the reasoning behind this recommendation: 
  • Fungicide residual – recent research by Dr. Rick Latin at Purdue University showed that more than 90% of the applied fungicide is depleted from within turfgrass leaves between 3 and 8 days. Furthermore, Dr. Paul Koch at the University of Wisconsin has demonstrated higher temperatures may result in quicker fungicide deterioration in turf leaves.
  • Disease inoculum is building – even though disease symptoms are not visible, disease inoculum is likely building within the turfgrass system with favorable weather. This is especially true for dollar spot if early spring applications were not made, if low rates are used and/or intervals are stretched, and/or contact products have been relied on heavily throughout the season.
  • Turfgrass health is compromised – High heat naturally depletes carbohydrate reserves of cool-season turf and this is compounded by limited fertility, low mowing, and (potentially excess) growth regulation to control green speed or clippings in fairways.
  • Excessive plant growth – In areas not regulated, cool-season turf has been growing very fast throughout the summer due to higher microbial activity releasing nitrogen from soil and timely rainfalls.  Fungicide residual activity in the turf leaves is likely reduced due to the growth and increased mowing. 
  • Acute disease pressure is high – combine the first four points with fluctuating soil moisture levels, high humidity, and warm temperatures, and dollar spot and brown patch has been exploding on golf course greens, fairways and tees.
  • Other factors play a role – spray volume, nozzle selection, droplet size, contact vs. systemic activity, and fungicide formulation can all impact length of control.
  • Bottom line – numerous factors play a role in reduced fungicide efficacy so be proactive and increase rates and/or tighten intervals when conditions are favorable for disease development. Though tempting, try to avoid skipping early season applications, and maintain higher rates and consistent intervals all year.
  • Need more info? – Contact your Bayer Area Sales Manager if you need assistance.

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