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New rice varieties: Some disease risk

All rice varieties have strengths and weaknesses. Even though we talk about both when a new variety is released, however, growers often focus on the yield potential and ignore a weakness that can cost serious money if planted and managed wrong. So before you plant this spring, take some time to consider the following:

Wells: This high-yielding Arkansas long-grain (40 inches tall) rice has one main weakness — neck blast. Wells is susceptible to blast, just like LaGrue.

I walked a few fields in 2000 where neck blast reduced yield more than 50 bushels per acre. While I do not believe Wells is as susceptible as Newbonnet, it can be hurt under certain conditions.

To minimize blast risk, Wells should be planted early (April) in wide-open fields where a 4-inch deep flood can be maintained during the summer. Tree-lined fields, hillside fields that are difficult to water, late-planted fields, fields in river bottoms or other “foggy” areas, or fields with limited water will put Wells at higher risk of damage.

Scout Wells fields for leaf blast on a regular basis and be prepared to apply Quadris or Benlate if needed.

Wells is moderately susceptible to sheath blight and straighthead, similar to Drew, and is susceptible to the minor disease false smut.

Wells also has many strengths, including exceptional yield, okay milling and very good standability. It has excellent seedling vigor, emerging in early-planted locations, heavy clays, and minimum-till seedbeds better than most varieties.

A big plus for Wells so far is that it has not had any problems with kernel smut, so Tilt fungicide should not be needed on Wells.

Cocodrie: This is a recently released semidwarf long-grain rice from LSU with excellent yield potential, very good milling, and good standability. Its major weakness in Arkansas has been straighthead. If you have fields with a strong history of straighthead, do not plant Cocodrie on them. On fields with any question about straighthead, drain and dry as soon as possible according to the DD50 report.

Joint movement in Cocodrie is very fast so you can't mess around if you need to drain. Most Arkansas growers kept Cocodrie off the bad straighthead fields last year and we did not have widespread problems. Naturally, I got to walk a handful of fields with major straighthead and it took most or all the yield in these cases.

We also consider Cocodrie to be very susceptible to sheath blight, similar to Cypress, but it did not seem quite as susceptible as Cypress in many fields last year. Suspect fields should be scouted for sheath blight shortly after midseason.

Under Arkansas conditions, Cocodrie is also susceptible to kernel smut and false smut, similar to Cypress. Both smut diseases are strongly increased by high rates of nitrogen fertilizer. Fields where more than 160 units of nitrogen have been used have had the most consistent smut problems. In fields with a consistent history of kernel smut, growers can use Tilt fungicide at 4 to 6 fluid ounces per acre during the boot stage to prevent the disease.

Earl: This is a newer medium-grain rice from the LSU rice breeding program. In my experience with Earl in Arkansas so far, it has not had many disease problems but has tended to lodge at quite a few locations. In general, these locations had too much nitrogen applied.

In my plots, the yield and milling of Earl have been excellent. Earl has been less susceptible to blast than Bengal so far in Arkansas. Earl has had considerable kernel smut at times in plots that were heavily fertilized.

RiceTec XL-6 Hybrid: We had quite a bit of this hybrid rice last year in Arkansas. Most growers had high yields but the milling quality was very erratic. Hopefully, the milling problems were due to last year's weird weather and will improve this year.

As far as diseases, only straighthead is a major risk for XL-6, as long as growers follow RiceTec's nitrogen recommendations (low rates). I have not seen any other disease problems with the hybrid under the low nitrogen rate system. However, growers who increase the nitrogen rate beyond the recommendation will greatly increase the risk of lodging.

CL121 and CL141: These are two of the Clearfield rices, and may or may not be available in 2001. I had very limited opportunity to look at the disease reaction of these varieties under Arkansas conditions last year and hope to increase my evaluation of them in 2001.

Both appeared very susceptible to sheath blight in various Arkansas plots so they should be managed like other sheath blight-susceptible varieties until we have a better handle on them.

CL141 was rated very susceptible to leaf blast in Arkansas plots while CL121 did not have much in side-by-side plots. However, based on other tests including the Arkansas blast nurseries (Fleet Lee), both should be viewed as potentially susceptible to blast until more is known under different growing conditions.

Both varieties had problems with stem rot in plots with weak fertility that I inspected, but this is true of most rice varieties.

Neither variety had much problem with straighthead in test plots last year, so straighthead tolerance is probably a strength.

From what I heard and saw, both varieties had good yield and milling quality and were very early to harvest.

While I sometimes get carried away looking at the risk potential of rice varieties, it is clear from many tests that the newer varieties have better yield and profit potential than older varieties. There is an awful lot of information to help you. I hope you will use it. It is not enough to just pick a good variety and plant the whole farm in it. Nowadays, pick the variety that fits the field and manage it for maximum yield and minimum risk.

Information is available through local Cooperative Extension Service agents, grower meetings, and experienced rice consultants.

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

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