Current Crop Situation:
Jason Kelley, Wheat and Feed Grains Extension Agronomist
Arkansas Wheat has had a tough week with nearly all of the state receiving flooding rains, high winds, and in some instances damaging hail. Many rivers and streams have or will be flooding causing many acres of wheat to be flooded. Hard to believe that just a few days ago, many areas of the state were in need of rain and were considered to be in a drought!! The recent rainfall over the last several days has raised concerns about Fusarium head blight (Scab), especially in Northeast Arkansas, where some wheat is still flowering. Dr. Gene Milus will discuss Fusarium head blight suppression options later in this newsletter. Despite all of the rainfall and storms, much of the crop still looks good at this point. Below are observations from county extension agents and wheat research verification coordinators from this week.
Andy Vangilder and Ron Baker, Clay County Extension Agents report that as much as 12 inches of rain has fallen this week, with higher amounts being reported just north in Missouri. Many roads are impassable at this point. Fortunately much of our wheat was planted on higher ground this year so at this point we don’t have a lot of wheat under water, except for some field bottoms. Big concern now is scab, since much of our wheat is flowering or just finished flowering. Foliar diseases in wheat have been low so far this year.
Randy Chlapecka, Jackson County Extension Agent. We have received on average 5 inches of rain this week, and we are going to have flooding on the White river that will cover some wheat fields. We have some hail in some areas, but fortunately it was small and appears to be only isolated areas. We do have some areas of fields where the wheat is lodging, especially on ends of fields where it was double planted or doubled up on nitrogen fertilizer. Our wheat has finished flowering and is near the milk stage. Overall the wheat on high ground with good drainage still looks good. Foliar diseases have been low and Barley Yellow Dwarf virus is evident in some fields.
Chris Grimes, Wheat Research Verification Coordinator, reports that many fields in Northeast Arkansas still look good. Overall lodging from winds and rain was less than I was expecting after hearing all the rainfall amounts and wind speeds. Foliar diseases that I have been seeing include low levels of stripe rust and Septoria.
Lafayette County – Joe Vestal, Lafayette County Extension Agent. Overall our wheat still looks good. We have gotten about 4 inches of rain this week and some fields have some lodging problems that occurred earlier this week and from storms last week. Foliar disease pressure has been low this year. Growth stage on most of our wheat is milk to soft dough. On average I would say we are a couple days ahead of schedule as far as development compared to previous years.
Central and Southeast Arkansas:
Grant Beckwith, Arkansas County Extension Agent reports that the county has received approximately 9 inches of rain this week. We have had reports of quarter size hail and lodging of some wheat fields due to high winds and heavy rain. Overall considering how much rain we have had most fields still look good.
Steven Stone, Lincoln County Extension Agent reports that across much of Lincoln county rainfall totals of 8 inches or more are common. We did have hail on Tuesday this week that ranged in size from ping pong ball size to as large as tennis ball, so needless to say we do have some hail damaged wheat. Many roads are flooded, so the full extent of the damage is still to be seen. Wheat growth stage is mostly milk to soft dough stage.
Robert Goodson, Phillips County Extension Agent reports that 11 inches or more of rain has fallen this week. Most of our wheat was not planted in flood prone fields, so hopefully we don’t lose much wheat to flooding. Most of our wheat is in the milk to soft dough stage.
Brent Griffin, Prairie County Extension Agent. Stripe Rust has made a really good push for development in the last 10 days. A majority of the acres were sprayed with a fungicide 10 to 14 days ago. A few BYD calls and some Septoria coming up the plant much like last year. We have been receiving 1/2 to 1″ showers over the last three weeks when much of the wheat was heading to flowering, so I have some concern about scab. Little or no Prosaro went out that I know of, mainly Quilt XL at heading. We have a lot of damage from glyphosate drift here, so it is hard to say what the yield potential could have been and will be.
Kevin Norton, Ashley County Extension Agent reports that about 2.5 inches of rain has fallen this week. We have missed some of the bigger storms and our wheat is still standing pretty good and overall looks good. Growth stage is soft dough.
Steve Kelley, Wheat Research Verification Coordinator. We have gotten hail damage on the South Arkansas County and Lincoln County fields this week. Our Lafayette County field has substantial lodging last week, but has stood back up to some degree.
Arkansas River Valley and Northwest Arkansas:
Lance Kirkpatrick, Logan County Extension Agent reports 6 to 8 inches of rain has fallen this week. Most of our wheat is planted on fields that don’t have flooding problems, but we still have lower ends of fields that currently have water on them. We do have wheat that has lodged from the heavy rains and winds. Our wheat growth stage is mainly milk to early soft dough.
Gene Milus, University of Arkansas Plant Pathologist. Fayetteville received 12-15 inches of rain over the last 6 days, and it is still raining. Wheat plots are saturated but generally in good shape. Most lines have flowered recently or are flowering now. Stripe rust is well established in the stripe rust nursery. Fusarium inoculum (corn kernels) has developed mature fruiting bodies in the head blight nursery. BYD is widespread in plots that did not get any insecticide in the fall, but plants do not seem severely stunted. Some bacterial streak was found. The Vegetable Substation at Kibler is closed because both roads to the station are flooded. Wheat plots there should have remained above flood water.
Scab (Fusarium head blight) – Dr. Gene Milus, Plant Pathologist
Although the current risk for scab is still low across most of Arkansas, recent rains have made conditions more favorable for scab by raising humidity levels. The risk of scab development will increase if warm, moist conditions persist. A forecasting model for predicting scab epidemics based on flowering date and weather data is available at http://www.wheatscab.psu.edu/riskTool_2011.html. It is easy to use and has been fairly accurate in previous years.
In addition to weather conditions, the risk of scab also is affected by the relative susceptibility of wheat varieties and to some extent by the previous crop and tillage practices. Scab reactions for some varieties can be found in the most recent Wheat Update (http://www.aragriculture.org/News/wheat_update/wheat_update_2010.pdf). Wheat grown after corn is at high risk because the Fusarium fungus that causes wheat scab also causes stalk and ear rot of corn and produces a lot of spores on corn debris that is left on the soil surface. Scab risk is greater with no till and minimum till wheat after corn than with conventional tillage because of the greater amount of corn debris left on the surface.
Scab development and mycotoxin levels in grain can be suppressed by a timely application of certain fungicides. The optimal application window is from flowering through about 5 days after flowering is complete, but this is highly dependent on when wheat florets get infected. Wheat south of I-40 is well beyond this window. Wheat in Northern Arkansas may still be in the optimal window, but time is running out to apply a fungicide for scab suppression. Prosaro, Caramba and Folicur fungicides have a 30-day harvest restriction, meaning that there must be at least 30 days between the application and harvest. Prosaro (6.5 fl oz/a) and Caramba (14 fl oz/a) have the greatest activity against scab. Folicur (4 fl oz/acre) and generic formulations of tebuconazole have lesser activity. Other fungicides that are registered on wheat either have no activity against scab or have the potential to increase mycotoxin (DON) level in grain.
Fungicide efficacy against scab is greatest if the fungicide is applied before infection occurs. Given the dry conditions before the recent storms, the Fusarium fungus that causes scab likely has not produced many spores yet, and little or no wheat infection has likely occurred as of April 27. Applications made during the next few days on wheat that is not more than 5 days past flowering likely will have close to maximal efficacy against scab and comply with the 30-day harvest restriction.