Popular varieties susceptible: Growers watch for blast in rice crop

Will blast take the Arkansas rice crop? A rather attention-getting question, don't you think? Rice blast is one of our most serious diseases, capable of causing major yield losses in any given year and even putting a few Arkansas rice farmers out of business in 1986 and 1987.

While sheath blight is more important most years, blast still scares most of us more. To me, this is because blast is so mysterious and so fast-moving. Sheath blight is more dependable, kind of a Joe Fungus disease, always showing up about the same time each year… always doing about the same level of damage depending on the field… you know, pretty reliable, predictable and manageable.

Blast, on the other hand, is a flashy, Hollywood disease. It moves in unexpectedly, makes a big mess right at the end of the season, and then is gone again for several years. Pretty scary.

The most devastating damage from blast occurs when it attacks the panicles during heading. You have all your money in the crop, it looks good, starts to head and WHAM! Neck rot! And all you thought you had were a few leaf lesions in the field.

Because of that behavior, our fungicide guidelines are based on prevention of neck blast and protection of as many panicles as possible. So if you choose to grow a susceptible variety and find leaf blast in the field, we recommend a fungicide application at heading.

If weather is favorable for blast, we currently recommend two applications — one at early heading and a second a few days later when the heads are most of the way out of the boot.

The cost of two fungicide applications will make you wish you had planted a different variety, especially if your wife sees the bill.

We have not had a serious blast year in a long time in Arkansas. Part of this is likely due to the weather patterns the past few years — hot and dry in July and August — and part due to the fact that most of our acreage has been planted in resistant varieties.

So why am I paranoid this year?

In Arkansas, we have planted 43 percent of our 1.6 million acres of rice in the variety Wells — which is susceptible to blast. We have another 10 percent in Bengal, also susceptible these days, and a few percentage points in LaGrue, Francis, Clearfield 141 — all susceptible.

The combined acreage is a big juicy target, unlike anything we have done in many years.

Next, we have found leaf blast in more fields this year than in the past several years. Currently, we have blast reported at some level in at least 12 major rice counties. At low levels, I admit, but still easier to find than I am comfortable with given the weather we have experienced.

Fortunately, the weather has not been that favorable for blast in the state… until recently. It has been raining recently, with milder temperatures and heavy dews — all as the early part of the crop starts heading. This makes me nervous.

If the favorable weather continues, will we get wiped out? No. But it will mean a lot of extra expense and worry for many farmers.

If you have a lot of Wells, LaGrue or other susceptible varieties, keep the flood pumped up to 4 inches and hold until time to drain. Fleet Lee has shown this to greatly minimize blast on our modern varieties.

Here's hoping for warm, dry weather and a pox on rice blast disease. One thing in our favor is that I am usually wrong about most everything, just ask my wife.

Rick Cartwright is an Extension plant pathologist with the University of Arkansas Division of Agriculture.

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