Arkansas Rice: Weather Concerns, Disease Difficulties, Boot N Applications

    Crop Progress

    “If we weren’t all crazy, we would go insane.”  Jimmy Buffett knows rice folks well.  The time to get out and scout is in the worst time of year to be out in a rice field.  But here we are.

    Continued hot conditions are making things a little tense around the state.  Several storm systems have moved through over the past week provided some with “dust-settling” relief, but not much else.  We can’t keep a solid flood on this rice, and when we can’t do that it makes it difficult to water beans and corn.

    Decisions must be made.  If you have a weak stomach, don’t go looking at how much water is in anyone’s reservoirs.  It’s not pretty considering we have another month or more to go to keep water on.

    Monday’s Crop Progress report showed us at 6% headed which is ahead of where I had us.  We’re probably easily at that point now, and it’s going to rapidly increase over the next two weeks.  By the end of next week we should have 30-40% of the crop heading.  So, we will have some rice draining before July is over, and possibly early rice cut around the first of August.

    Considering it wasn’t an early planted year, the sustained season-long heat is going to give us an early harvest.  We’ll see what happens between now and then.

    Fig. 1. Leaf blast reports are common.

    Fig. 2. Sheath blight progressing.

    Never Curse a Rain, But Bad Timing?

    Supposedly, we have rains in the forecast for this coming week.  Every little bit of rain will help, but will it be just enough to hurt?  Disease development is the concern with rain at this time.

    Leaf blast and sheath blight reports are becoming common right now.  This is partly due to our inability to hold a deep flood in prolonged high heat, and our high dew point keeping moisture in the plant canopy for longer in the day.

    If we drop temperatures into the upper 80s, that is arguably even better for disease development.  Throw in some rainfall and overcast days and that may really spur disease development.  Lucky us…

    Active scouting is key right now.  Remember that for blast – just because you find leaf blast doesn’t guarantee that you’ll get neck blast; but just because you DON’T find leaf blast doesn’t mean you can’t get neck blast.  More on blast decisions later.

    For sheath blight, we’re trying to protect the upper leaves in the canopy until 50% heading.  Just because you have a high percentage of stops with sheath blight doesn’t mean you automatically treat – it has to be moving up the canopy and threatening upper leaves.  Late applications for sheath blight management are generally not recommended unless it’s very common field-wide on a lodging prone cultivar, in which case a fungicide may help with late-season standability.

    Blast is Hard to Manage, Unpredictable

    One of the continued difficulties with making decisions on fungicide applications to prevent blast, is that blast is very unpredictable in our environment.  We can’t “scout and spray” because once you have neck and panicle blast it’s there to stay.  So we apply preventative fungicides based on what we “think” will happen.

    Neck and panicle blast infections occur as the panicle emerges out of the boot.  This is why we recommend a two-application approach to blast management with fungicides.  The first application goes out when primary tillers are at late boot (flag leaf collars visible) to 10% heading.

    The second application goes out when primary tillers have panicles 50-70% out of the boot (necks still in boot).  These two applications provide sufficient fungicide in the flag leaf and boot area to protect the neck and panicle from blast infection.  Each application should be at least 10 oz Quadris (or equivalent rate of other products).

    The single application approach to blast management with fungicides comes with additional risk – the risk increases the more uneven a field’s development is.  If going with a single application, target 30-50% panicle emergence from the boot (necks still in the boot).  The single applications should be 12 oz Quadris (or equivalent rate of other products).

    Fig. 3. Fungicide application timing for blast management by rice growth stage. Click Image to Enlarge

    Smut Management with Fungicides

    To be early is to be on time, to be on time is to be late.  Or at least that’s a saying I remember being told as a kid.  Still holds true today in many ways, including fungicide applications for smut management.

    Mid-boot (as flag leaf is emerging) is the optimum time fungicide applications to prevent smuts.  Late boot (flag leaf emerged, boot swelling) is getting too late for optimum fungicide performance.  And boot split is definitely too late.  Use at least 6 oz/acre of Tilt (or equivalent) to suppress kernel smut and false smut.

    Boot N Apps in Hybrid Rice

    As rice begins to head, it’s time for late boot nitrogen (N) applications in hybrid rice.  We recommend these applications at late boot (flag leaves all the way out) to when a few heads are starting to pop.  If applied earlier there is a chance for additional vegetative growth and plant height response that we don’t need.

    The benefits of the boot N application at this timing are primarily improved milling and decreased lodging.  A small yield bump can also be seen.  For most these benefits aren’t super obvious because each of the benefits is small on its own, but they add up to a lot.

    Table 1. Effect of boot N applications to hybrid rice, 2016-2017 (six locations). Click Image to Enlarge

    Insect Update

    Rice stink bugs (RSB) are on the move with rice beginning to head.  Hopefully with a lot of rice starting to head over a larger area, we can spread them out and minimize damage and the need to make insecticide applications.  Regardless, get to scouting!  Treat for 5 RSB per 10 sweeps the first two weeks of heading; treat for 10 RSB per 10 sweeps the second two weeks of heading.

    Yes, this means you may need to keep scouting after you’ve started draining the field!

    Insecticide applications for control of armyworms in rice is typically not recommended.  In later rice, it’s a concern if larvae begin to feed directly on panicles or clip flag leaves.  Otherwise it’s generally not advisable to target them with a special trip across the field.  We’re working on more specific thresholds, but for now it’s best not to treat until the “uh oh” moment.

    Fig. 4. Armyworm feeding on leaves in rice.

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