Herbicide Drift Is Not What It Use Be

Buehring, Former Extension Rice Specialist
By Buehring, Former Extension Rice Specialist May 18, 2012 11:36

Over last week or so, calls have become to trickle in on sick rice after the flood has been established.  In most of these cases, the rice does not want to grow with the fertilizer and a flood on it.  After inspecting these fields, signs of herbicide damage are evident on the foliage.  When most of the calls come in, the producers believe that it is either a fertility, insect or disease issue.  However, those issues generally occur in patches or spots where some areas are worse than others.  Herbicide drift usually occurs across the whole field with one side being worse than the other.  Also, rice that is on the levee can give you a general direction in where it came from.

With pigweeds taking on a whole new meaning in the delta.  Producers are not just making glyphosate only applications due to the high level of glyphosate resistance across the delta.  That is good that producers are aware of the pigweed resistance issue and are making herbicide adjustments to get control of this costly weed; however, it has been a headache trying to figure out exactly what has gotten on the rice other than just glyphosate.  Also, a lot of acres got treated with Gramoxone prior to soybean emergence for pigweed control.  There has not been much rice that I have looked at this year that did not have spots on the leaves from Gramoxone.  In addition, Gramoxone has been applied with other herbicides like Boundary which can confuse the problem.  As you can see, it can be a complicated mess when trying to figure out what the exact herbicide(s) caused the problem.

Even if we do not know the exact herbicide that has caused the symptoms here are some things to keep in mind.  Drift rates of herbicides that have preemergence weed control generally will not put enough on or in the soil to have a prolonging effect on the rice for the remainder of the season.  With Gramoxone drift, what you see is what you get.  Mostly what we have seen is just leaf speckling.  It does not translocate down into the plant to have any other effect.  I have been on calls where the rice leaves have speckles but the plants are showing signs of glyphosate drift.  On these calls, glyphosate is the main problem.  Also, glyphosate drift on rice becomes a whole different animal when it was applied with another herbicide.  In a lot of these cases, we do not know the exact herbicides that caused the problem.

Even though we may not know the exact problem that is going on in these fields, the recommendation usually stays the same.  If the rice is injured and a flood is established, begin to start taking the water off of the field.  Water tends to magnify the problem and makes the rice stress more.  Sometimes you do not have to let the soil get dry, but the rice does not need the pressure of deep flood.  Let the plants start to green up and show some signs of tillering or normal growth before reestablishing a typical flood.  Once normal growth begins to occur, the rice should be fine for the rest of the season.  However, some delay in maturity will be expected due to the herbicide drift.

Herbicide drift is one of the most hair pulling things you get involved with as a specialist and that can be said for the farmer whose rice is hit by it.  If we can help, give us a call.

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Buehring, Former Extension Rice Specialist
By Buehring, Former Extension Rice Specialist May 18, 2012 11:36
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