With the cooler temperatures here in the West coming in, you'd expect some slow down as far as disease development, NOT! Rapid blight and basal rot anthracnose continue to be issues on Poa greens in California. We're also seeing some junk diseases like Curvularia blight on warm season turf slowing down in the cool weather and algae developing on greens with the reduced day-lengths.
California Disease Summary
Dr. Naveen Hyder did a nice summary of the last four years of disease diagnostic data at the Crop Science Meeting in Pittsburgh a few weeks ago. A copy can be found here:
As you can see, Poa annua diseases like rapid blight, anthracnose, brown ring patch and algae are our top trouble makers, with over 50% of our samples being annual bluegrass, Naveen stated to the crowd "either we need to put even more resources towards annual bluegrass disease control, or figure a way to keep it out of greens." Much, much easier said than done....
Pythium in the PNW
As mentioned a few weeks ago, Pythium has been causing issues for superintendents in Oregon and Washington. We finally got an ID on some of the troublemakers involved. Samples from several courses were identified as having either Pythium vanterpoolii or P. torulosum, which can do perfectly well under cool (55 to 65 degree F) conditions, as long as its wet. I haven't had much experience first hand fighting these, but my gut feel is that under cool, wet conditions, many typical fungicides can knock down the Pythium, but it's too cool for the annual bluegrass to recover quickly. If it stays wet, the Pythium can re-emerge when the fungicides have "worn off" and damage turf again. In this situation, the lack of recovery from the turf due to cool conditions just magnifies the sucessive rounds of damage and frustrates the hell outta superintendents.
Annual bluegrass greens damaged by Pythium at Portland Golf Club (left) and several weeks later after multiple fungicide applications, blood, sweat and tears (right). Images from superintendent Forrest Goodling.
Thiophanate-methyl and Pink Snow Mold in Northern California
An interesting question was brought up to me this week about using thiophanate-methyl on annual bluegrass greens in parts of northern California. Some superintendents are using it to manage a problem (hint: rhymes with angina) and were wondering what the impact of that would be on resistance development for pink snow mold, which should pop up as our max. daytime temps start to drop below 65.
If one's using repeated thiophanate-methyl applications at a time when pink snow mold may be active - resistance is certainly an issue. Resistance to the benzimidazole fungicides (benomyl and thiophanate-methyl) was detected for pink snow mold back in the 1980s in Washington State. It's unknown what the current status is in northern California, but certainly, back to back, repeated applications of this fungicide will be putting one at risk for losing it for pink snow mold.
If one is using this approach, make sure to use other materials as front-line fungicides for pink snow mold control. PCNB, iprodione, polyoxin-D, the DMIs, mancozeb, & chlorothalonil and mixtures of some of these are all non-benzimidazole fungicides that can be against pink snow mold.
Signing off from the Left Coast until next week......