Sheath Blight Pressure Picks Up in Southwest Louisiana
By AgFax Media LLC, AgFax.com
OVERVIEW
Weather conditions improved immensely this week over much of our coverage area. Fields were drying up enough for farmers to finish preflood fertilizer and herbicide work, plus wrap up some replanting before the crop insurance cutoff.
Problem situations remain, particularly cases where farmers either lost levees to May storms or didn't have a chance to pull levees earlier. Muddy conditions held off levee work long enough that rice gained a good deal of size and some of that still hasn't gone to flood. See comments by Jarrod Hardke.
Fall armyworms have been building in rice in Arkansas. Rice water weevil pressure has been high, too, based on leaf scarring and adult activity in flooded fields. See comments by Gus Lorenz.
Sheath blight pressure has clearly picked up in southwest Louisiana. Heavy rains in that part of the state have likely put a dent in yield potential in rice that was heading or already flowering when downpours hit.
Johnny Saichuk, Consulting Agronomist, Ducks Unlimited, South Louisiana:
"I had a case the other day where southern green stink bugs were turning up in rice. It wasn't anything dramatic, but it's been a long time since I've come across that particular insect in rice.
"Things are mostly in a holding pattern, aside from people dealing with disease. We've definitely had too much rain. A wet June hurts yields. Partly, that's due to lack of sunshine. When you have an extended period of rain, the skies remain overcast, even when it's not raining. Rice needs plenty of sunshine, so this lack of it is not a good sign.
"Old farmers used to say that they made their best rice when they had to keep pumping water, and we sure haven't had to pump lately. In that kind of year they had ample sunlight. The next few days are supposed to be clear with no rain, which will help."
Dustin Harrell, Louisiana Rice Extension Specialist, LSU Rice Research Station, Crowley:
"The biggest factor in terms of crop development has been rain. It rained pretty much 12 days in a row. If it wasn't raining, skies were cloudy and overcast – but most days, it did rain.
"That really came at the wrong time for us in southwest Louisiana. The bulk of our rice was just beginning to head and some of the earliest rice was already flowering. These mid-day showers during flowering can cause at least some grain to go sterile – especially when a pounding rain falls.
"This weather trend also set us up for sheath blight. Conditions were perfect for it, and sheath blight has really blown up in the last week (from 6/8). In rice in later reproductive stages we need to be scouting and using appropriate fungicides.
"You reach threshold when 30% of your stops in the field are positive for sheath blight. If you're in an area with high rates of strobilurin resistance, one of the SDIII fungicides – Sercadis or Elegia – will be your only option.
"In a lot of rice we're also seeing South American rice miner (SARM) or leaf miners, and they've shown up in a big way over the last couple of weeks. Often, SARM feed on the leaf when it's still tightly rolled. When the leaf unfurls, linear areas across the width of the leaf tend to be damaged, which causes the leaf to droop over. Sometimes the top of the leaf falls off.
"Since SARM and other leaf miners feed inside the leaf blade or inside the whorl of the plant, insecticides can't reach them. The overall yield loss from the pest is probably small, even though the damage is very unsightly. In a normal year, rice will outgrow the damage. But we've had nearly 2 weeks of rain, overcast skies and humid conditions. So, rice hasn't been growing very fast and the damage from SARM really stands out.
"We're coming out of the wet weather pattern, at least temporarily. The sun is out and conditions look favorable until Sunday. But then more rain is in the forecast – 40% to 50% chances for 10 days after that.
"Overall, I still think we have a chance for a good yielding year, but the key now is to maintain control of sheath blight. This probably is the most sheath blight we've had in several years. Typically, we can expect a 20% to 30% yield reduction with bad sheath blight."