Volume 1 Issue
2 May
28, 2004
Cold, Wet Soil and Herbicides
What a difference a month makes. April weather seemed
to signal an early spring with the potential of a drought.
Now it looks like we are in a wet cycle again, only with
May average daily temperatures that are from 4o
to 25o F below normal according National
Weather Service records. For those who have applied
preplant incorporated or preemergence herbicides, there
isn’t any doubt the compounds have had enough rainfall to
be activated. An appropriate question to ask now, however,
is has this weather increased the risk for crop injury
from the soil applied herbicides? Probably. Corn and
soybean tolerate many herbicides by metabolizing or
breaking down the compounds they have absorbed. Wet soil
conditions increase the amount of herbicide that is
available for uptake by plants, but cold soils reduce or
slow the plants ability to metabolize the herbicide.
While these conditions increase the
potential for good weed control, they also increase the
risk of crop injury. In most fields, herbicide injury in
the spring is temporary and does not result in yield loss.
Significant herbicide injury usually occurs when other
stress factors that reduce the crop's herbicide tolerance
are also present. Other factors may include varietal and
hybrid differences in their level of tolerance to the
herbicide, deep planting, soil crusting, poor quality
seed, seedling diseases, etc.
 A
quick review of herbicide injury symptoms from soil
applied herbicides is included in Table 1. An excellent
publication that provides color pictures of herbicide
injury can be found at:
http://www.extension.umn.edu/distribution/cropsystems/DC3832.html
Carlyle Holen Extension IPM
Specialist
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