Field Notes, July 12, 2010, Bacterial Panicle Blight, Panicle Blast, Potassium Deficiency, Tip Burn, Herbicide Injury

Late Season Potassium Deficiency

I have been told that some folks in Arkansas refer to this problem as “Arkansas high yield disease” because it is almost always associated with high yields. We saw it last year mostly in CL151 and that has been the predominant variety again this year.  The most distinctive symptoms are the narrow brownish lesions between the leaf veins.  Leaf analysis last year indicated a potassium deficiency.

Unknown tip disease

From the pickup truck fields affected with this problem might resemble those affected by potassium deficiency, but they are not the same.  This problem has characteristics of leaf scald and bacterial leaf streak.  Again they are not the cause.  We do not know the cause.  Dr. Groth has been unable to isolate fungi from it.  Because it is in fields also showing Bacterial Panicle Blight the question is whether this is another manifestation of the disease.  We don’t know.

Bacterial Panicle Blight

The symptoms at right are of Bacterial Panicle Blight.  It has been around for a number of years.  At one time we thought it was an environmental problem because it is almost always associated with high night-time temperatures.  The typical symptom is the brownish discoloration of the kernels while the panicle branches remain green.  Because it is caused by a bacterim, fungicides are of no benefit.

Panicle Blast

Rice blast is a well known disease that reportedly is especially severe in Arkansas this year.  It can be distinguished from Bacterial Panicle Blight by the dried, brown panicle branches.  It is caused by a fungus thus fungicides are of benefit when applied at the correct time and at the right rate.

Shortened internodes and adventitious roots caused by herbicide injury

When a consultant brought stunted plants to me the first thing I did was split the stems.  It was clear the internodes were much shorter than they should have been at that stage of development.  It was probably caused by herbicide applied to the field.  We visited the field a week later and it is producing normal panicles.  Maturity is delayed and plants are shorter.  Impact on yield is uncertain.

Stacked nodes versus normal internodes

 

In this photograph the plant at right shows normal internode elongation while the one at left has the stacked nodes (shortened internodes) typical of the plants shown in the first photograph.

Command injury on Jazzman rice

 

One of the early questions about culture of Jazzman was its potential susceptiblity to Command herbicide.  I did not have a good answer until this year.  The field where this injury was observed was adjacent to a field of a long grain variety that showed no symptoms.  The reaction of Jazzman apparently is similar to that of the medium grain varieties which are more sensitive to it.

Tags: Bacterial Panicle Blight, herbicide injury, panicle blast, potassium deficiency