Anthracnose & Summer Patch in California
'Hey - Did-ya Miss Me?' Anthacnose was plentiful in the UCR diagnostic lab this week
I was back in California this week and greeted with triple digit temperatures - normally I'd say the dry heat of California is better than the steamy heat of Washington DC, but 112 degrees in Riverside was still pretty bad!
I always say that anytime we get wide temperature swings, anthracnose is likely to rear its ugly head, and this last week was no exception - Naveen was getting quite a few of these samples in the lab.
As John had mentioned earlier this week, summer patch has been pretty active on annual bluegrass greens and we saw it on a few samples in California as well. Back in the 'good old days' of the 90's, it seemed like anthracnose and summer patch control went hand in hand, but recent developments have resulted in some 'complications'.
As we all know, anthracnose has become the primary concern of most guys out there with annual bluegrass greens, but summer patch can often be a hidden problem. Here are two observations regarding summer patch development this year.
#1 Targeting Anthracnose but Forgetting About Summer Patch
Sixty-five to sixty-eight degrees soil temperature in the spring is the magic range for initiating anthracnose & summer patch control programs with 2 to 3 applications of DMI-fungicides like Banner MAXX, Trinity, Triton, Tourney or Torque, but after that, control diverges quickly for these diseases. Fungicides like the Heritage (azoxystrobin) and Insignia (pyraclostrobin) are my top choices for summer patch control (thiophanate-methyl, e.g. 3336, is also a consideration), and should be applied monthly in the summer to keep summer patch in check. But....as we all know, anthracnose resistance to the QoIs and benzimidazoles in many locations makes these ineffective for anthracnose control. For mid-summer applications, products like chlorothalonil (Daconil), fludioxonil (Medallion), polyoxin-D (Endorse/Affirm) and Signature (Fosetyl-Al + StressGard pigment) are my go to materials. DMIs can also be effective, but applied in the summer heat may cause some unwanted PGR effects.
Superintendents worried primarily about anthracnose may be applying anthracnose-fungicides but forgetting to use Heritage & Insignia on a monthly program. As a result, summer patch can break through what seems like a good program that is unfortunately tailored specifically for anthracnose.
#2 Compass vs Insignia in Rapid Blight Control Programs & Effect on Summer Patch
Rapid blight is another disease that California superintendents battle in the spring and summer, and Compass (trifloxystrobin) and Insignia are the 'go to' systemic fungicides for rapid blight control (mancozeb is our only contact option), but differ in their physical properties. Compass is very strong as a foliar fungicide, but less systemic than Insignia and will not give you effective summer patch control. If you've been using Compass regularly in the summer, remember that you could be under-gunned for summer patch control, and have to apply additional materials.
Bottom Line: Anthracnose, summer patch and rapid blight management require specific fungicides - choose wisely and know what fungicides won't give you any overlap in disease control.
Anthracnose Rescue Fungicide Programs
If you have anthracnose breaking out on greens, it is most likely that you (i) have had a serious stress event, (ii) are too lean on fertility or (iii) have had a lapse in fungicide protection in your program.
Notice that 2/3 of the 'issues' are not fungicide-related. Correcting cultural practices and fertility is the top priority, but here are some thoughts on a 'rescue' program for active anthracnose outbreaks.
1. DO NOT BOMB IT WITH QOIs/STROBIES OR T-METHYL FUNGICIDES EVEN IF THEY STILL WORK FOR YOU. That is a recipe for resistance, big time! Anthracnose is already a high-risk pathogen when it comes to QoI and benzimidazole fungicides, and using them as 'eradiciants' in this way increases the chance of selecting out resistant populations.
2. CHLOROTHALONIL IS YOUR FRIEND. This is partially why I encourage guys to save up some of your 10 or so chlorothalonil applications for the summer. Chlorothalonil will not 'cure' existing infections, but can kill spores developing in acervuli and prevent new infections (if you let your foliar anthracnose go all the way in to the crowns, you're hosed, don't wait til that happens as you won't be able to get on top of it with fungicides in the summer). Being a contact fungicide, you will need to apply frequently to ensure that you have lasting coverage on plants. Applying the normal label rate, at a shorter application interval, is likely more effective than the max. rate once or at longer intervals.
3. MEDALLION, ENDORSE & AFFIRM --- These are 'limited systemic' fungicides and can give you added control of anthracnose, but are at moderate risk for fungicide resistance. I would not encourage them to be used as 'eradicants' but you can apply them to help with protecting plants once you have the active outbreaks arrested with aggressive chlorothalonil use. Right now, there is no resistance to these, & we want to keep it this way for the time being.
4. SIGNATURE, ALIETTE, & PHOSPHITES --- These have for the most part, 'indirect effects' on anthracnose, and will not work as 'eradicants'. The data I've seen shows that the active molecule in these fungicides is not super-toxic to anthracnose, and provide protection via induced plant defenses or other mechanisms; and you guys know how I feel about StressGard pigment being a good thing for annual bluegrass in the summer. Tank mixing them with your chlorothalonil will give you added protection but they will be acting on healthy plants vs. new infections and not directly killing the active anthracnose.
F-Bombs, Nematodes and Cee-Lo
Ok - I've gotten some (for the most part) good natured ribbing from some guys this week about my comments on Turf Net regarding what we know about nematodes.
Call me crass, but the F-word is strongly correlated with the discussion of turf diseases; it's one of those words that in its various forms has use as a noun, verb or adjective, especially when discussing anthracnose, summer patch or rapid blight, and annual bluegrass in general.
On the other hand, in all seriousness regarding the comments, we really don't know enough about nematodes on turf, and really really don't have enough chemical controls for the problems - making me drop the F-bomb to drive home the point.
Compared to the 30 or so university turf pathologists in the US and dozen or so different fungicide active ingredients, we have like 4 turf nematologists (Crowe, McClure, Wick & Mitkowski come to mind) and 1 nematicide (Curfew), plus any Nemacur stockpiled in the shed, that can control nematodes down in the soil .
You know I love me some fungus, but considering the issues caused by nematodes like root knot, stem & gall (Anguina), spiral, sting and others, and more importantly - the high amount of "mis-information" about nematodes and their control out there - it's a good time to put some attention and funds towards this. That's my 2% of a dollar.
Finally, if you can't get enough of the F-Bomb, check out Atlanta-based Cee Lo's new music single and song here:
(WARNING: DEFINITELY NOT SAFE FOR WORK OR CHILDREN)
If you're not offended by the F-bomb and like Old School Motown-Style R&B, it's certainly worth a listen. I suspect they will have taken this one down from the internet by the time you read this blog today, but I'm sure you'll hear about this one soon.
OK - Back in DC as of the Morning and Signing off from the Right Coast.....