With temperatures hitting 90's and 100s in parts of SoCal last week, it's no surprise to see some death and destruction, but bacterial wilt may not necessarily be the cause. Here's some basic info about the disease that may help you recognize this potential issue.
Bacterial wilt is caused by Xanthomonas translucens or X. campestris, and tends at attack stressed, shaded or low fertility turf under warm or hot conditions. High humidity and mositure make the disease more severe. Symptoms start off as small yellow to whiteish spots that can spread and eventually turn into small reddish dead spots.
Two highly informative articles on the disease, symptoms, and control can be found here and here.
Control of the disease can be tough since there are no chemicals that offer complete control of the disease.
Because of our relatively dry west coast conditions, I would say that outbreaks of bacterial wilt are kind of like coordinating a trainwreck. You need some very specific conditions for the disease to fire, but when it does, the results can be spectacular.
Although the pathogen is difficult to control directly with chemicals - cultural controls such as raising mowing height, managing irrigation, reducing mechanical stress and avoiding mowing wet greens, can be implemented.
Most importantly, an accurate & timely diagnosis needs to be made for this disease. Symptoms can be identical to those caused by other stresses and it's difficult to accurately diagnose once the infected tissue is already dead (which is especially true if you let the disease explode before you take a sample). If you suspect the disease - get samples sent to a diagnostic lab right away.
In Other Local News....
The weather is getting a little better through much of the state with temps cooling down into the high 70s to 80s in most parts of the state, although parts of the Central and Inland Valleys will see 100s this week .
Not much change in expected, diagnosed and reported diseases. Anthracnose is still pretty active, and we have some gray leaf spot brewing in Orange county on both perennial ryegrass and kikuyugrass. Night time temperatures above 68F in southern and central California could mean Pythium outbreaks on cool season turf. Watch for this disease on low lying areas or those where drainage is poor/water accumulates.
Signing off from the Left Coast until next week....