Clubbed Roots in Corn
Glenn Nice, Weed Diagnostician, Department of Botany & Plant Pathology,
I often come across things that I have not
seen before. I
would be fooling myself to think that I have seen it all, I wonder
if anybody has. These oddly formed brace roots on a corn
plant were sent in to the P&PDL. Some of the brace roots
were showing clubbed secondary roots coming off of the brace roots
If I were to see this on the primary and secondary
underground roots I would have suspicions that a dinitroaniline
(Treflan, Sonalan, Prowl) that had been incorporated into the
soil might have been involved (Figure 2). However, I have not seen these particular
symptoms on the brace roots before. The dinitroaniline herbicides
are a group of herbicides that are generally used preplant incorporated,
preemergence on the soil surface. The dinitroaniline herbicides
inhibit a plant’s cells ability to go though mitosis and
form cell walls. If the developing roots come in contact
with the dinitroaniline this can lead to swollen stubby secondary
roots (Figure 2) or other wise known as “clubbed roots”. This
can sometimes lead to lodged corn because the root cannot brace
the corn plant into the soil.
There has been some mention of corn lodging
suspected to be a result of pendimethalin injury. The University of California
recommends Post applications of pendimethalin as a culti-spray
after brace roots have formed; warning that it may cause lodging1. This
might be recommended to assure that the brace roots are already
pegged down into the soil to minimize contact with the herbicide. Michigan
State University reported that in coarse textured soils with low
organic matter after heavy rains that pendimethalin could move
in the soil to the root zone and cause injury and lodging2. The
Cornell Integrated Crop and Pest Management Guidelines for Vegetable
Crops mentions that in sweet corn applications or pendimethalin
in wet conditions may lead to poor brace root development leading
to lodging3. In the 2005 Iowa State University Weed Control
Results, a study looking at postemergence applied pendimethalin
reported brace root malformation4.
Excluding the information previously discussed
above, there was not much in the diagnostic and scientific literature
regarding the malformation of brace roots due to dinitroaniline
herbicides, suggesting that it is not a common occurrence. However,
the symptom seen on this corn’s brace roots is suggestive
of dinitroaniline injury. If the secondary roots were to come
in contact with a high concentration of dinitroaniline when they
reached the soil it might lead to the “clubbed root” symptoms
typically seen in injury situations from dinitroaniline herbicides. In
this situation, it is possible that pendimethalin was postemerged
applied just prior to the brace roots reaching the soil. Thus
the brace root tips were exposed to a high concentration of pendimethalin
and these injury symptoms resulted.
Herbicide Treatment Table. Accessed
on August 21, 2006.
2. Jim Kells. Accessed on August 21, 2006. Excessive
rain and soil-applied corn herbicides.
Integrated Crop and Pest Management Guidelines for Vegetable
Crops. Accessed on August 19, 2006.
4. Owen, M.D.K., R. G. Hartzler, J.F. Lux, and D.D.
State University Weed Control Results, 2005.
Click image to enlarge
Figure 1. Corn plant with clubbed primary and secondary brace roots.
Figure 2. Dinitroaniline injury on underground roots.