Cream Leaf What?

Cream leaf what? That's the exact response I've heard from superintendents over the past several weeks when I tell them their ultradwarf bermuda putting greens have a disease known as cream leaf blight. To answer your first question, cream leaf blight is not a new pathogen to turfgrass. It has been documented on creeping bentgrass and tall fescue. As more ultradwarf bermudagrass replaces creeping bentgrass for putting surfaces here in North Carolina, we will likely observe more new diseases. This disease has been diagnosed on both 'Champion' and 'Mini Verde' and we are in the process of complete confirmation of the causal fungus via DNA analysis.

 

Typical white patch symptom observed on ultradwarfs
in December/January in North Carolina

Cream leaf blight is caused by the same pathogen that causes pink patch, Limonomyces roseipellis. Pink patch is often found in close association with red thread, which is caused by the fungus Laetisaria fuciformis. Pink patch and cream leaf blight vary slightly in their morphological features, which we are able to detect under the microscope. For those of you who are plant pathology geeks, pink patch produces clamp connections and cream leaf blight does not. Otherwise, from what we've observed, the two appear identical in the field and we will most likely refer to it as cream leaf blight since that seems to match the stand symptoms the best. One unique characteristic is the mycelium will twist into "rope" like structures, as seen below.

Mycelium twisting into "ropes" for both cream leaf blight and pink patch (25x)

Close up of cream leaf blight hyphae twisting into a "rope" (200x)

While we don't know much about cream leaf blight on bermudagrass yet, we have only observed cosmetic damage and nothing that leads to turf loss or significant reduction in playability. We have been recommending fungicide applications of products like 26GT, ProStar, Heritage, Insignia, or Disarm since they have been proven performers with pink patch/red thread complexes.

If you are observing this type of symptom at your course and have questions, feel free to contact us!

Getting ready for life without Rubigan

Is this what life will look like without Rubigan?

A lot of people have heard about Rubigan going off the market in December 2012. If you have questions or concerns, please check out yesterday's post on turfdiseases.org entitled "What will we do when Rubigan is Rubi-gone?".

We are planning a lot more spring dead spot research this fall in response to this issue, so we'll probably be in touch with some of you about the possibility of doing research at your facilities.

Spring rings on MiniVerde greens

We don't have a whole lot of MiniVerde in North Carolina yet, but we've had several reports of widespread rings appearing on MiniVerde greens as they are greening up this spring. Interestingly, we haven't had similar reports from superintendents with Champion or Tifeagle greens.

The rings on MiniVerde are typically about 1 foot in diameter and are very irregular in shape, not perfectly circular. The turf on the outer edge has a yellow or reddish-brown cast to it.

Any time we see this type of spring symptom on warm-season grasses, we automatically think that it is large patch caused by Rhizoctonia solani. Based on our initial look at samples, it is definitely a Rhizoctonia disease, but we are isolating to confirm exactly which species is the culprit.

Either way, recovery should be very quick once sunlight and warm temperatures come and the bermudagrass starts growing aggressively. In fact, two superintendents reported that the symptoms have already become less noticeable as the bermudagrass continued to green up.

A fungicide application probably isn't necessary, but could help to speed up the recovery process if the symptoms are very severe or widespread. Any systemic Rhizoctonia fungicide, such as azoxystrobin, flutolanil, or fluoxastrobin should provide good control. Check out the Disease Management Utility for a complete list of products labeled for large patch control.