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20
Mar
2014
Plan your field size to effectively manage autumn decline or straighthead
Author: Yeshi Wamishe, Extension Rice Plant Pathologist

“Drain and dry” is the recommended protective or rescue strategy to manage these two abiotic phenomena in rice.  Historically, straighthead disorder (Picture 1) has been associated with old cotton fields where arsenic pesticides were once used.  Although arsenic produces straighthead symptoms, it may not be the only cause.  Straighthead is a severe abnormality that may cause up to 100 percent grain yield loss.  Unfortunately, once a field has a history of this disorder, chances are the problem remains permanent.  Some varieties are resistant and do much better than others in problematic soils.  However, if the variety is known as susceptible or moderately susceptible, it is recommended to “drain and dry” before panicle initiation.  The best way to time this process is by using the University of Arkansas DD50 program (Rice DD50).   To read more on straighthead symptoms and management, go to managing for straighthead starts early.

Picture 1. Straighthead blanks kernels and causes severe yield loss

Picture 1. Straighthead blanks kernels and causes severe yield loss

Picture 2. Autumn decline: Roots blacken and rot and later crown will be occupied by opportunistic fungi (left); Healthy roots pulled from the levee are clean due to soil exposure to oxygen (right). Allowing oxygen to enter the soil will aid in the recovery of symptomatic plants to become normal again.

Picture 2. Autumn decline: Roots blacken and rot and later crown will be occupied by opportunistic fungi (above); Healthy roots pulled from the levee are clean due to soil exposure to oxygen (below). Allowing oxygen to enter the soil will aid in the recovery of symptomatic plants to become normal again.

autumndecline2Autumn decline, also known as akiochi disease of rice or hydrogen sulfide toxicity, causes black crown and root rots in rice (Picture 2). This phenomenon was a concern in 2004.  More recently it has been seen in rice fields across the state of Arkansas in 2012 and 2013.  From our observation, this problem can occur in rice fields without a history.  Scouting your rice fields ,particularly with a history starting two weeks from permanent flood, is highly recommended.  Although the primary symptoms may look nutrient-deficiency related, it is important to note that this phenomenon cannot be corrected with the addition of nutrients.  Symptomatic plants show premature death of lower leaves, casting yellowish color across the field when seen from a distance (Picture 3).  A yellow cast is indicative of a late disease symptom but still there is time to rescue the crop from having complete yield loss.  Hence, immediate action needs to be taken.  First you need to diagnose the problem correctly and then act accordingly to stop further damage.  If it is autumn decline, “draining and drying” is the recommended option.  If you know the field has a history of this phenomenon, draining and drying need to be done before panicle initiation as indicated by DD50 program for straighthead.

Picture 3. A field with early autumn decline symptom with yellow cast

Picture 3. A field with early autumn decline symptom with yellow cast

In the process of “draining and drying”, timing is unequivocally important related to the growth stage of the crop and how soon you may be able to remove and replenish water in the field.  You need to be thoughtful in managing these problems. The crop should not be deprived of water for long duration particularly in the reproductive stage.  Therefore, it would be strategic to get your field to a manageable size so you can move water on and off the field quickly.  This would be beneficial especially to fields with a history.  To read more go to weather and akiochi.

For questions contact your county agents or the author at ywamishe@uaex.edu.


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