Arkansas Rice: Overviews On Fertility, Diseases Going Into July

Where did some of this rain come from this week? Out of the north, apparently, so we’re catching it from all directions now.

The weather is actually great right now (6/28) for growing rice. Upper 80s and next week in the low 90s with partly sunny conditions. We’re accumulating a lot of DD50 units to keep this crop rolling but are avoiding stressful conditions.

Comment of the week: “Go home 2019. You’re drunk.” No matter which direction we turn, something strange happens this year. Too many firsts to count, and just when we have it figured out, we’re wrong.

Around half the crop should be reaching half-inch internode elongation. For pureline varieties that means more midseason nitrogen if using the two-way split approach. See last week’s update for more discussion on optimum timing, but around half-inch IE and 4 weeks since flood establishment is the sweet spot.

While already mentioned in an earlier update, more rice reaching midseason has potassium (K) deficiency showing up All the rain has likely contributed to this situation. Tissue test to be absolutely certain as we can correct even out to late boot. If a deficiency is confirmed, apply 100 lbs of potash (60 lbs K2O) into a stable flood.

Disease Update

To date, we have received reports of leaf blast from Randolph County on Titan and Lawrence County on Diamond. Most rice planted relatively early is now past green ring. The weather is getting warm with morning dew and rain chances.

Moisture on the leaves in the form of  dew, fog, and frequent rain fuels leaf blast. A 9- to 14-hour moisture period on the leaves is enough for spore germination. The disease can start early at tillering and continues in the season to provide spores that infect panicles causing neck and panicle blast.

Remember: neck and panicle blast if severe with no protection can cause near 100% grain loss.

If leaf blast is detected early in the season on a susceptible variety, neck blast is often predicted and at least a one-time protective fungicide is justified. However, the absence of or inability to detect leaf blast on a susceptible variety in a field with a history of blast does not guarantee that neck and/or panicle blast won’t show up later in the season.

Remember: blast pathogen spores can be carried by wind and unexpected infection can happen under favorable weather conditions and inadequate water and fertility management.

Continue scouting for leaf blast. Leaf blast is often managed by increasing flood depth to at least a 4-inch depth. However, if a fungicide application is needed in cases of severe leaf burn down, it can possibly be aligned with the need for smut management if your field has a history of either false or kernel smut or both. Protective fungicide application timing to suppress the smuts is from early to mid-boot.

Remember: blast is managed with strobilurin and the smuts with triazoles fungicides.

Note: Protective fungicides for neck and panicle blast should generally be managed separately from smuts or sheath blight. To read on blast management read the answers to common questions at common- questions on blast management.


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