Greetings from the hot, humid, and dry Deep South!

Greetings from the Deep South! I am Maria Tomaso-Peterson, Ph.D and come to you from Mississippi State University where I conduct research and teaching in turfgrass pathology. I am very pleased to be invited by my fellow turfgrass pathologists and bloggers to participate in sharing insights from the Gulf Coast States.

The first half of 2011 has been coined the year of extremes…….. no, I am not referring to politics, but to weather conditions across the United States! South of the Interstate 10 corridor, rainfall deficits are making their way into the record books. Our fellow superintendents in Texas are experiencing the driest seven months on record. When I visited New Orleans, LA in May, I was amazed at the drought stress exhibited by the palm trees along Canal St. South Mississippi and Alabama, as well as the panhandle of Florida (the whole state, actually) are well below average for annual rainfall.

With that, fungal disease pressure has not been the issue thus far. The primary challenge is delivering adequate water to keep the turf alive. Of course, the greens are the primary receivers of irrigation, followed by tee boxes, and fairways (sparingly). The roughs have gone dormant, but not to worry, the bermudagrass will be back! Despite the dry conditions, there are still some pest issues that have to be managed. I thought I would share some of those issues with you in my inaugural blog post.

My fellow turf pathologist out of Oklahoma State University, Dr. Damon Smith, had an excellent review on nematodes in creeping bentgrass back in June. As we know, sand-based putting greens are an ideal environment for plant parasitic nematodes; couple that with root zone temperatures above 65 F for the better part of a growing season in the South, one can see how nematode populations can get out of control in one growing season. Sting and root knot nematodes are the most common species identified from dwarf and ultradwarf bermudagrass putting greens. At the Mississippi State University Nematology Laboratory, analysis results have shown bermudagrass green samples with sting in excess of 500 per 100 cc soil and other samples with root knot greater than 1,200 per 100 cc soil. The affected areas of a bermudagrass green may appear light green to yellow, thin turf density, reduced clippings, and the turf does not respond to nitrogen or irrigation. The damage may be widespread but more often observed in clusters. Symptoms of sting damage on bermudagrass roots (left) include root-pruning and necrotic lesions. Root knot galls are easily detected under a stereomicroscope.

In the photos below, root knot galls can be seen in bermudagrass roots (left) as well as pearly-white, mature female root knot nematodes embedded in a bermudagrass root (right).

For those who stock-piled Nemacur, spot treatment is recommended for control. Curfew® is a soil fumigant which requires a custom applicator and is labeled for use in Mississippi, Alabama, and Florida. Curfew has been granted a 24(c) label from EPA for use on golf courses in Texas and Louisiana. Non-fumigant products, some biologically-based, are also commercially available for nematode control.

Another pest that has been active on drought-stressed turf is the bermudagrass mite (BGM), Eriophyes cynodoniensis, which can be found wherever bermudagrass is grown throughout the United States. Mite injury is most severe to bermudagrass during hot and dry conditions such as those experienced this growing season.

The BGM feeds underneath the leaf sheath. Once feeding commences the leaf tips turn yellow and the leaves become twisted. The internodes shorten resulting in a rosette or witch’s broom appearance. Under severe outbreaks, large areas of turf turn yellow, thin out and may die as a result.

Insect damage was observed on bermudagrass fairways and roughs earlier this month in Texas. When infestations are high enough to cause obvious symptoms of BGM damage, it is necessary to irrigate the affected turf to minimize damage to the plants. Insecticides are available for BGM control; however repeat applications are necessary to reduce the populations.

Several locales along the Gulf Coast have received rain over the past week. These localized rain events are a welcome sign for those folks in the drought-stricken regions. The rains drive up the humidity in the turf canopy which in turn is favorable for disease development. I will be scouting the Deep South for disease outbreaks so I can report back to the Turfgrass Disease Blog in the near future. In the meantime, just remember…..never underestimate the power of a fungus!

A Cornucopia of Disease in Southeast Asia

I sometimes find such healthy grass that I have little disease to write about, but this week was an exceptional one. I went from Kanchanaburi to Bangkok, Singapore, and Da Nang, seeing a number of grasses and on them an assortment of pathogens. Click the thumbnails for a full-size image and description.

If there were an award for diseases, seashore paspalum would win this week, with two different unidentified diseases and slime mold and dollar spot, with a bonus for some extraordinary drought stress. In the image below, there is an unidentified patch disease and dollar spot on a seashore paspalum fairway in Bangkok. And you can see the drought stress in the drain lines going to the catch basin in the background. But wait! Can you see the patch of Zoysia matrella in the center-left of the photo? The Zoysia matrella that is free of disease and doesn't have the drought stress of the paspalum even though it is growing in the drain line? Seashore paspalum does not grow well at all in Southeast Asia in areas of low soil moisture content.

Seashore paspalum grows wild in tidal swamps and in intertidal zones. Which is exactly where I found it growing on the beach at Da Nang (below), in its natural environment, and free of diseases. But come in from the beach a short distance, where the high tide does not reach, and I found wiry Zoysia matrella growing in the dunes.

There was brown patch on bermudagrass at Vietnam and bermudagrass white leaf, which I think is the most unsightly disease, on bermudagrass at Singapore and Vietnam.

Most of the diseases, you notice, were on seashore paspalum and bermudagrass. I saw two types of broadleaf carpetgrass this week, both free of any disease. This grass thrives in the umbrageous conditions so ubiquitous in tropical Southeast Asia, as does zoysiagrass.

And for those more interested in cool-season grasses, you probably read with some interest the post from Dr. Kerns and Dr. Soldat a few weeks ago about managing potassium on cool-season turf. I'm fascinated by the Park Grass experiment and its results showing that potassium and lime application cause a proliferation of dandelions and other weeds, and the most recent issue of the Green Section Record has an article with some insights into that experiment and how the results "carry lessons of high importance in the growing of golf turf."

Clouds With No Rain

I've seen a lot of drought-stressed turf in Southeast Asia over the last two weeks. In some areas near Bangkok there has been no rain since October 2009, and with temperatures now sometimes exceeding 40° C (104° F), the rains cannot come soon enough. The drought has damaged roads, causing many to collapse and crack at Patum Thani, severe drought has been declared in 35 provinces of Thailand, and the government has advised rice farmers to defer planting until rains come. Turfgrass managers are restricting irrigation to priority areas because there is very little water remaining in their reservoirs.

The University of California have an excellent publication entitled "Managing Turfgrasses During Drought" which I recommend as a general reference.

Fairy ring symptoms are more apparent under these dry conditions, and that is the main disease I have seen recently. The common practice of sandcapping golf courses in Southeast Asia makes it more difficult to manage the turf when irrigation water is in short supply, and the symptoms of fairy ring are more intense on these arenaceous soils. At the Manila American Cemetery, more than 30 ha of Zoysia matrella is maintained similar to the conditions we would want for a golf course fairway. The fairy ring is most intense on the sole sandcapped area, the entrance Mall of the cemetery.

Answer for 5/24/09: Wilted turf in a sand-based system.

Click here to see the original posting (5/24/09).

In the case of the photos posted in the quiz, this was a case of several factors that resulted in the perfect storm. This research putting green has two different soil mixes. The healthy turf on the left was predominantly a native soil, while the discolored turf on the right had been excavated about 4 to 5 inches deep and filled in with sand several years ago. The end result was a fast wilting of the turf during a high and dry period. In this case, the turf starting to head south in a matter of a few hours. Exacerbating the problem and likely putting it over the edge was an excessive thatch layer and moderately aggressive vertical mowing. Some things that I found interesting and helped in the diagnosis were:

1. Notice the wilted turf surrounding the vertical mowing. The only area damaged, however, is the area where sand is the primary growing medium. Turf growing in the native soil (left) appears healthy. (The area on the far right was growing in sand, but not vertically mown)


2. Turf around the irrigation head was likely under less drought stress and therefore did not wilt.


3. Wicking. Bentgrass growing in the sand, but within about 3 inches of the native soil putting green was healthy. This was the result of the water "wicking" into the drier sand mix and therefore providing enough moisture to keep the turf from wilting.


The photos can be deceiving and most probably thought that this problem was caused by a misapplication of some herbicide or fungicide. The bottom line is that turf diseases "generally" don't appear in straight lines! This is a good example of how turfgrass managers must investigate well beyond the visual symptoms. I just can't wait for the TV show next season..."Turfgrass CSI".