July 25, 2014 No. 2014-20
Dr. Jarrod Hardke, Dr. Gus Lorenz, Dr. Bob Scott, & Dr. Yeshi Wamishe
The weather and its effect on the rice crop is becoming a daily roll of the dice. The up and down temperatures are playing games and the rice doesn’t seem to like it. Last week, according to the DD50 program, 77% of rice should’ve hit 50% heading by today; however, after it was updated with this week’s cool weather, it dropped that number to 63% (Table 1). The reason for the change – DD50 bases calculations on 30-year average temperatures and is updated daily with current weather, resulting in the flexible numbers.
We get a “normal” July weekend of upper 90 temps followed by another cool down – mid 80s all week. Based on this past week, expect more heavy dew sets and increased disease levels and movement.
The issues of this week will likely continue into next week with the similar weather pattern. Plant development and heading will be uneven, making fungicide and insecticide application timings difficult.
For those of you who are just ready to get this season behind you (which is most of the folks I’ve spoken to lately), Table 2 has currently projected harvest dates. These dates are the estimates of when the crop will reach 20% grain moisture. If the current deviation from normal temps continues, those percentages will continue to be pushed later.
The 2014 Rice Expo will be held next Friday, August 1 at 8:00 a.m. at the Grand Prairie Center in Stuttgart. We hope to see you there for all the activities and field tours.
Table 1. Percent of rice acres set to reach 50% heading during listed weeks of 2014 according to DD50 enrollment.
Table 2. Percent of rice acres set to reach harvest moisture during listed weeks of 2014 according to DD50 enrollment.
Picture 1. A rare evenly heading rice field.
Out Standing in Your Field
The Rice Stink Bugs Are Still Here
Scout! Early morning and late evening best times to scout. Threshold – 5 per 10 sweeps first 2 weeks, 10 per 10 sweeps second 2 weeks.
Continued Disease Development
Sheath blight has again started creeping up. Semi-dwarf long-grain cultivars are more susceptible than tall ones. Continue scouting. Weather appeared favorable for the disease making cultivars such as XL753 show more than 50% positive stops. This seems a bit unusual for this cultivar.
We have received more reports of leaf blast from Monroe Co. on Jupiter, CL261, and Jazzman-2; and in Lee Co. on Roy J. Although blast usually starts at the edges of fields closer to tree lines or higher ground where the flood is low, lesions for the disease were detected across the field indicating the pathogen’s potential to spread. Weather conditions are extremely favorable for the disease and its spread. Long dew periods and leaf wetness favor pathogen development and slow winds encourage it to spread. In some fields inadequate flood depth management appeared to be the major cause for the disease incidence and severity.
Prior to yesterday, leaf blast was reported in Clay, Randolph, Lawrence, White, Prairie, Lonoke, Woodruff, Monroe, Arkansas, Jackson, and Greene Counties on Jupiter, CL151, CL152, Francis, Roy J, and Caffey.
Scout and develop a neck blast prevention plan.
Field conditions that favor blast:
- Poor water-holding capacity.
- High nitrogen fertilization.
- History of blast.
- Longer dew periods (surrounding tree lines, near river bottoms, etc.).
- Low potassium levels.
(Susceptible cultivars #1 favorable condition!)
Weather conditions that favor blast:
- Frequent light rains.
- Extended cloudy days.
- Slow winds.
- Warmer days & cooler nights.
*All contribute to longer dew periods.
*Remind you of current weather at all?
Mistakes leading to fungicide failure:
- Waiting too long to apply fungicides.
- Using the wrong products.
- Using reduced rates of fungicides.
- Scout fields!
- Correctly diagnose disease (make sure it’s not herbicide/fertility/environmental issue rather than blast).
- Maintain a deep flood (>4 inch depth).
- Apply fungicides for PREVENTION of neck blast:
- 1st app – late boot to 10% heading (Picture 3).
- 2nd app – 50-75% heading (Picture 4).
- If the neck has emerged from the boot (Picture 5) you are too late to manage neck blast – keep the fungicide in the jug (unless you need it for other diseases).
- If you’re a born risk-taker and decide to go with only one application, make it when the main tillers are 1/3 to 1/2 way out of the boot (see note below).
*Note: a single fungicide application approach for prevention of neck blast is NOT RECOMMENDED. In years with heavier blast pressure and conditions very favorable to blast, 2 well-timed applications may only result in 80-90% control; while a single application may only provide 50% control at best.
Glyphosate drift has begun to show up in unexpected places now that heading has begun. Pictures 6 & 7 show the results of that drift on rice panicles and leaves.
Glufosinate drift is also showing up as many replant soybeans have been Liberty Link varieties. Symptoms are obvious (Picture 8) but have never really been shown to have yield limiting effects.
Occasional fields have been showing up with sulfur deficiency (Picture 9) the last couple of weeks. If late-boot or after, no treatment will help plants recover, only cosmetic improvement.
Enroll fields in the DD50 Program here: http://DD50.uaex.edu.
Problems or questions: email@example.com / 501-772-1714.
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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.