Should I water that in?

This is easily the most frequent question I get from golf course superintendents during the growing season. It is a difficult question, and there isn't always an easy answer.

We know that watering fungicides into the root zone is important for effective control of root diseases. However, in the real world, golf course superintendents apply fungicides to control a combination of root and foliar diseases, but we don't always know what effect watering-in has on foliar disease control.

To answer this watering-in question, you need to identify the primary disease you're trying to control, know where this pathogen attacks the turf plant, and understand how the selected fungicide moves in the plant after application.

In most cases, if a root disease is the primary target for a fungicide application, then it should be watered-in immediately after application. Once the spray dries on the leaves, it will be locked into the foliage and will not get into the root zone. Exceptions to this rule are the true systemic fungicides, like fosetyl-Al and the phosphite salts. These products are translocated downward in the plant and do not need to be watered-in.

The Fungicide Selection Tool, a new feature on our TurfFiles website, can help you select the best application technique for your fungicide applications. After selecting your turf species and the diseases you are trying to control, a list of fungicides is displayed. The list is ordered based on average efficacy against the selected diseases. After selecting a product or products to apply, you are taken to a page that displays mode of action, efficacy rankings, risks for fungicide resistance, rates and application intervals, and application instructions for each selected disease.

Don't neglect your nozzles!

As your college interns start to filter to the course from academic studies, now is the perfect time to fire up the sprayer in preparation for the 2009 season. This gives you the opportunity to ensure that your equipment is in proper working order AND gives the students the opportunity to get hands-on experience with calibration techniques that many have only heard about in the classroom.

Many websites and books are available to assist in the calibration of your equipment. In preparing for this update, I also came across a calibration software package that TORO offers for download from their website. While calibration of your equipment is important, another factor that should not be overlooked are the nozzles that you select to control turfgrass diseases.

Research conducted in the past few years has revealed that nozzle selection plays an important role in the suppression of turfgrass diseases (Read GCM Article). In particular, the control of foliar diseases such as dollar spot and brown patch can be improved by selecting nozzles that improve spray coverage. One major problem with this is that nozzles producing excellent coverage generally have increased potential for drift. Our research has shown that utilizing nozzles that incorporate air into the droplets (air induction) provide the best of both worlds. Here are some keys to improving disease control.

1. Consider the location of the pathogen. Fungicides for root diseases generally need to be applied in greater volumes of water (>2.0 gal/1000 sq ft) and/or watered-in following application. Foliar pathogens should be suppressed with a nozzle that produces excellent coverage.

2. Air induction nozzles provide excellent control of foliar pathogens and have relatively low potential for drift. TurfJet nozzles (typically supplied with many sprayers) generally offer poor disease control, especially where lower water volumes (~1.0 gal/1000 sq ft) are utilized.

3. Nozzles should be changed at least once per year (twice per year in some cases). Always buy an extra nozzle to use as a comparison when determining if your nozzles need to be replaced.