Agfax Buzz:
    June 29, 2012
    rice-root-blackening-arkansas-06292012

    Arkansas Rice: Root Blackening – 12 Observations About Known and Unknown Factors

    AgFax.Com - Your Online Ag News Source

    By Yeshi Wamishe, Assistant Professor and UA Division of Agriculture Extension Plant Pathologist

    The actual cause for root blackening and rotting in rice is still a mystery. We still do not have strong evidence why in some soils roots turn black and rot in anaerobic (flooded) conditions (Fig. 1).

    However, we know that opportunistic fungi grow in the crown (Fig. 2) and the whole root system shuts off and the plants eventually die.

    Below are 12 observations made by Drs. Chuck Wilson and Rick Cartwright of the University of Arkansas, Cooperative Extension Service in 2004.

    1. The problem was noticed first and appeared worse where water entered the field (cold water paddies).
    2. The crown rot symptom were found on scattered plants in cold water checks in many fields across the state; however the widespread problem affecting large areas of a field was confined to only a handful of fields in the counties mentioned at that time.
    3. All affected fields had high soil pH.
    4. Soil types varied from silt loam to clay loam.
    5. All wells observed at the time were pumping iron-laden (orange) water.
    6. All severely affected fields had water pumped on them a lot (it seemed) so they suspected the water temperature might have stayed consistently lower in these fields than others – and other well water related factors might be spreading further than normal.
    7. Wells observed at the time were reported as 100-150 ft deep.
    8. Cultivars affected at that time were Cocodrie, Wells and CL161, although most were probably susceptible.
    9. The fields had several herbicides, and not all were the same ones.  Grandstand appeared to be the only consistent one used in most of the severely affected fields, but it was not thought to be the original cause.
    10. The paddy rice was affected; the levee rice was not.
    11. The soil and roots smelled mucky but not like rotten eggs.  Sometimes they smelled a little nasty (sewage) but not always.  In fields in previous years where hydrogen sulfide toxicity was suspected, the water and roots did smell like rotten eggs.
    12. They found islands of healthy rice in some affected paddies (Arkansas County) and healthier streaks and patches in other fields (Lonoke Co).  These were surrounded by sick rice.

    Last week, we visited a field planted in Cl 151 and CL152 in Northeast AR with similar symptoms described above. The rice was at 1 inch internode elongation.  Most of the field was affected although symptoms were worse in the deeper water areas and near water inlets.

    Many plants had rotted or rotting roots, and the rot was spreading upward into the crowns.  Once removed from the water, the blackening on the roots and lower part of the plants disappeared.  Although it is likely unrelated, we noted many tiny snails hanging on the leaves in this field (Fig . 3).

    In the past, diagnostic soil, water and plant samples have not indicated conclusive or consistent factors associated with the condition.  Previously, Wilson and Cartwright indicated that “growers managed the problem by draining to aerate the crowns and roots and after a few days recovery with new white lateral root growth evident, re-flooded the fields and the rice made it.

    Afterwards, we advised these growers to simply drain and dry the soil in these fields as for straighthead (straighthead timing), and this has helped prevent the problem from re-occurring.  While draining at straighthead timing does not completely cure this problem (it can reappear later in the season), it interrupts the process long enough to allow roots to grow out and sustain the plants to normal harvest date.”

    Whatever the cause, growers have learned that aeration of the system is their only management option when the problem is noticed and most have figured out how to carefully drain down until they can see new white roots forming, then reflood.  Growers are very careful not to let the soil get dry if the rice is midseason or later, as rice in these later stages is so sensitive to drought stress.

    It is a risky balancing act and they watch the field daily during the process, looking for new white roots each morning, and it shows how good our farmers are at managing this crop under difficult circumstances.  Most have told us that doing nothing resulted in huge yield losses in the past as root systems completely died as did plants during the late boot to heading and grain fill stages, when water demand gets so high.  Without a root system, the plants simply wilted in the flood and eventually passed on.

    Fig. 1Fig. 1 Fig. 2Fig. 2 Fig. 3Fig. 3

     

     

     

     

     

     

     

     

     

     

    Tags: ,

    4 Responses to Arkansas Rice: Root Blackening – 12 Observations About Known and Unknown Factors

    1. Joe Melvin says:

      Read the article on blackening roots in rice. We’re having that problem. We’ve had problems with hydrogen sulfide toxicity before. The symptoms look very similar. I’m not smelling the rotten egg smell associated with hyd sul tox. But rather the raw sewage smell. We’ve read where amonium sulfate directly contributes to hydrogen sulfide toxicity. We quit using ammonium sulfate for a few years, until this year. Now we’re seeing the blackening of the root system (black crown rot, black root rot). Whatever it actually is. Is there any relation to ammonium sulfate and this blackening of the roots? Also, The fields that it has been reported in, are they in a rotation? And/or have cut ground from leveling?

      • Owen Taylor says:

        Thanks for your comment. You should receive an email from us with contact info for someone with more info.

    2. Mary Provance-Bowley says:

      Have you looked into arsenic as a potential causal agent? The avalability of arsenic is affected by pH, temperature, iron oxides, and reducing/oxidative conditions. Additionally, roots tend to accumulate As. There is a 2007 publication that you might find informative, Arsenic: Potential for human exposure. Available online at the below link. http://www.atsdr.cdc.gov/toxprofiles/tp2-c6.pdf

    Leave a Reply

    Name and Email Address are required fields. Your email will not be published or shared with third parties.

    Agfax Rice News

    USDA Changes Deadline: Yield History Update, Reallocation Base Now Due March 312-27

    Pinnacle’s Sanders in 9 Southern States with Newest Acquistion2-27

    Louisiana Rice: Losing Methyl Bromide Creates Challenge For Bin Insect Control2-27

    NRCS Invests $84M Natural Disaster Funds in 13 States2-26

    Pesticide Drift: Calm, Still Days Are Most Dangerous – DTN2-26

    Keith Good: Global Soybean Issues; Vilsack on Crop Insurance; Food Stamps Re-Revisted2-26

    Farm Bill Deadlines Approach: 17 Questions – Answers for Landlords2-25

    U.S. Energy: ExxonMobil California Refinery Outage – Implications for Oil Markets2-25

    Propane Inventories, Prices Dip2-25

    Gas Prices Continue to Climb2-25

    Diesel Prices on the Rise2-25

    Keith Good: Exports Damaged by Port Delays; Ethanol Production Cutting Back2-25

    Keith Good: Senate Ag Committee Hears from Farmers2-25

    AFB Rice Close: Another Big Crop Expected2-24

    Arkansas: Deadlines Approaching for 2014 Farm Bill Considerations2-24

    DTN Fertilizer Trends: Slow Climb Higher; Canadian Rail Strike Fuels Prices2-24

    No More Cuts: 392 Farm, Nutrition, Conservation Groups Urge Congress to Stop – DTN2-24

    Fertilizer: Verdesian Adds Polymer-Based Option To UAN Protectant2-24

    New York: National AgrAbility Training Workshop, Rochester, April 13-162-23

    Planter Maintenance: 17 Points Not to Overlook – DTN2-23

    Keith Good: Landowners vs. Farm Tenants; India Resumes GMO Field Trials2-23

    Keith Good: Govt. Shutdown Looms; Cotton Rally Waning2-23

    Farm Succession: 3 Ideas for Mastering the Transition – DTN2-23

    Income Tax Primer: 19 Points to Know About Trusts and Estates2-23

    Drones: FAA Planned Regulations. Batman Won’t Like 1 of them.2-23

    WTO Ag Rules: Some Countries Not in Compliance2-23

    Keith Good: West Coast Ports – “Normality Not Yet on Horizon”2-23

    AFB Rice Close: Export Support Unable to Hold2-20