Drs. Jarrod Hardke, Yeshi Wamishe, & Bob Scott
June 8, 2018 No. 2018-15 www.uaex.edu/rice
“I wanna go fast” – Ricky Bobby. May/June 2018 would be right up his alley. This crop continues to move along at breakneck speed. The high temperatures look to continue for the next week with little end in sight. A couple of rain chances, small ones, are out there but I’ll have to see it to believe it.
Easily over half the crop in the state has gone to permanent flood. That mark was probably surpassed by the end of last week. Given the continued heat most of the remaining acres will be to flood in short order.
Fields that have been flooded are dealing with the usual difficulties of extremely hot weather. Maintaining flood depth, or any flood at all, is proving difficult on a number of fields. This can have potential negative effects on nitrogen efficiency and weed management.
With the large number of acres pushing to spray and fertilize so they can flood, applicators are considerably behind. With that, we’re attempting to clean up many weed control messes. We’re seeing good success with that but it hasn’t been cheap. And to add to the uncertainty someone has attached the rice market to a yo-yo…
Rice Leaf Blast Alert: First Report on Titan at Early Tillering Stage
In 2018, initial symptoms of leaf blast on rice cultivar, Titan were reported from Lonoke County on June 6th at early tillering developmental stage. The field is surrounded by trees and has a history of blast. Titan is a medium-grain rice and was rated MS to blast since its release. It has been less susceptible than Jupiter to blast in our greenhouse test and under field conditions.
Initial symptoms of blast may not be clear (Fig. 1) and can be confused with herbicide damage or brown spot. To confirm symptoms, leaves with lesions should be incubated in moist chamber (Fig. 2) to encourage sporulation. Spores can be clearly viewed under a compound microscope at 100X magnification. Spores are typically pear-shaped with 2 septa as in Fig. 3. Fungicide application may not be needed unless blast is burning down the leaves. Leaf blast is often suppressed by increasing flood and maintaining a depth to at least 4 inches.
The spores of the fungus are lightweight and can be carried by wind for several miles. In fields with a history of blast planted with susceptible varieties, two timely, protective fungicide applications are recommended for late-season neck and panicle blast, which are the most devastating forms causing potentially near 100% grain yield loss. Distinctive lesions from leaf blast are diamond-shaped with ashy centers (Fig. 4).
Often first blast report on rice in Arkansas comes from the 2nd to 3rd week of June. It seemed unusual to see blast this early. However, the hot conditions have made flood depth management difficult and combined with heavy morning dews could contribute to increased blast infection.
Fig. 1. Blast lesion before sporulation.
Fig. 2. Incubation in moist chamber to enhance sporulation.
Fig. 3. Blast fungus spores under magnification.
Fig. 4. Distinctive lesions of rice leaf blast.
Herbicide Injury and Herbicide Drift a Major Concern of Late
Herbicide injury calls have been common for the past week. Under the hot, dry conditions we’re seeing injury that we don’t normally encounter. Under cool, wet conditions herbicide injury isn’t uncommon as rice as difficulty metabolizing them; however, under the stress of hot, dry conditions we seem to be encountering it yet again but on the opposite end of the spectrum. Some Clearfield hybrid rice fields have been injured by Newpath, particularly when used in combination with other ALS herbicides such as Grasp (Fig. 5). Clearfield hybrid injured by Newpath should be kept wet with a shallow flood for best recovery. For non-Clearfield cultivars with Newpath drift the field needs to be dried up.
Fig. 5. Herbicide injury to Clearfield hybrid rice from Newpath and Grasp.
In other fields we have continued to field calls about Delayed Phytoxicity Syndrome (DPS) where normally rice-safe herbicides are made toxic to plants by anaerobic fungi. You usually see this show up about a week after flooding and when severe clearly displays rigid, “crunchy” rice and fish-hooking of young tillers.
Many soybean fields are also being sprayed with glyphosate and we have to be careful around rice fields with a good number of fields approaching reproductive growth (green ring). Rice hit with glyphosate during vegetative stages can typically recover and perform just fine. Rice hit during reproductive stages can see severe yield losses as it affects panicle formation (Fig. 6).
Fig. 6. Malformed leaves inside the stem as a result of glyphosate drift in reproductive rice.
Rice Field Day Scheduled for Friday, August 3rd
The Rice Field Day at the UofA Division of Agriculture Rice Research & Extension Center is scheduled for Friday, August 3, 2018. More details will follow.
New DD50 Program is Live!
Check out http://DD50.uaex.edu for the overhauled DD50 Rice Management Program. We have tried to make this version extremely user friendly, but in doing so it is a little different than the old version. If you run into any issue, please call or text me directly at 501-772-1714 or send emails to email@example.com. It also works great on mobile phones and tablets.
Arkansas Rice Updates are published periodically to provide timely information and recommendations for rice production in Arkansas. If you would like to be added to this email list, please send your request to firstname.lastname@example.org.
This information will also be posted to the Arkansas Row Crops blog (http://www.arkansas-crops.com/) where additional information from Extension specialists can be found.
More information on rice production, including access to all publications and reports, can be found at http://www.uaex.edu/rice.
We sincerely appreciate the support for this publication provided by the rice farmers of Arkansas and administered by the Arkansas Rice Research and Promotion Board.
The authors greatly appreciate the feedback and contributions of all growers, county agents, consultants, and rice industry stakeholders.