If rice is to have any benefit as a rotation crop for reducing pigweeds in the soil seed bank, you must achieve 100 percent control. A lot of rice fields have excellent pigweed control in the paddies but a few stray pigweeds on the levees. A big mamma pigweed getting sub-irrigated on a levee with all the nitrogen it wants can make over a million seeds.
The telephone calls I’m receiving remain quite challenging because the book was thrown out this year before we ever started. When you throw out the book, sometimes you have to guess. I don’t know if I can guess any better than anyone else, but I give it my best shot.
I am getting a lot of calls about pigweeds in rice. I have written since 2005 that this weed would become a monster. Normally, pigweed is a weed that you pay to pump water to control — except on the levees.
However, it is not always that simple. Sometimes they were missed with the burn-down treatment and you wind up with big pigweeds in little rice. Sometimes —— due to the extreme plant populations that often occur — they can compete vigorously with the rice before it is big enough to flood.
In a lot of cases the best pigweed stands occur on sandy fields or hillside fields that are difficult to hold a flood on. Some growers tell me they used to control them with water but can not now.
Nothing with pigweed surprises me.
There are no great options for pigweed control in rice. Most are resistant to the ALS inhibitors, so that takes out Newpath, Beyond, Regiment, Grasp, Permit, Londax and Strada as options. Facet and Command do not have much activity on them and propanil alone does not have near enough activity.
The best two herbicides to use preflood are Aim and Grandstand. Neither is great, but they are the best we have.
On small rice and small pigweeds, I usually recommend propanil plus Aim. This treatment will kill some, burn some and miss some. It will also light the rice up pretty good, so your tolerance for burn needs to be relatively high.
As the rice and pigweeds get some size, I usually switch the recommendation to Aim plus Grandstand or propanil plus Grandstand. This treatment will kill a few and nose the remainder over and sit on them to buy some time until flooding. Then, if possible when the rice will tolerate it, flood deep and hold it.
The best midseason treatment for pigweed is 2,4-D where it can be used. If an early treatment and/or the flood do their job, hopefully the pigweeds will be relegated to a levee problem.
The levee treatment restrictions on 2,4-D seriously need revisiting. It would be impossible to drift 2,4-D from the west side of the ridge to the east side with a normal levee application. However, I do not see any movement in that arena.
I have been assured by Plant Board personnel that pigweeds on levees are a justification they will approve on a permit application — IF the application is filled out properly.
I receive numerous complaints each year about permit applications being denied. When I have inquired about a few of these, it is usually because the applications were not filled out properly rather than the justification offered not being accepted.
If rice is to have any benefit as a rotation crop for reducing pigweeds in the soil seed bank, you must achieve 100 percent control. I drive by a lot of rice fields that have excellent pigweed control in the paddies but a few stray pigweeds on the levees. A big mamma pigweed getting sub-irrigated on a levee with all the nitrogen it wants can make over a million seeds.
I am beginning to get the aquatic calls I expected with the water seeding and seeding into backwater. Newpath plus Londax and Beyond plus Grasp are the heavy hitters in Clearfield rice. In conventional rice, Londax plus Command and oil early can be a good treatment. RiceBeaux plus Command or Londax can be good early and as the rice gets well-rooted the best treatment becomes Grasp or in some cases Regiment.
I am getting a lot of calls in soybeans from folks with unrealistic expectations from a potential burn-down treatment on large marestail and pigweed. The first rule of thumb is you have to start clean. In situations where the weeds are too large, you simply have to use tillage and nobody wants to.