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herbicide spraying
NOT TOO COLD: Burn down herbicides are less effective the colder air temperature. Wait for a warm up for best results.

Do you need to wait for warm weather to burn down weeds?

Grain Gleanings: Advice on controlling wormwood, best spring wheat planting dates and more.

You’ll soon have to make a lot of decisions about planting and managing crop pests. The following is some answers to questions early season weed and disease control.

Wait for warm up to burn down?
A reader asks: Should I apply a burndown herbicide, especially Sharpen, when it cool?

Answer: “Burndown contact herbicides such as Sharpen and Verdict, and systemic herbicides such as glyphosate and phenoxys (2,4-D), are much less active at low temperatures. Daytime temperatures of 50 degrees F or above is ideal, and nighttime lows above freezing. Adjuvants can increase the activity of these herbicides in adverse conditions such as these. Use 1 to 1.5 pt/A of MSO or 1 pt/A of an HSMOC (MSO based) and 8.5 lbs/100 equivalent of AMS, or at least 1.25 gal/100 gal of UAN. Cold temperatures may also plug nozzles with some mixtures.” — Rich Zollinger, former North Dakota State University Extension weed specialist.

Differences between systemics
"There’s an important difference between what 'systemic' means when it refers to herbicides and when it refers to fungicides. Systemic herbicides will move throughout the plant. A systemic fungicide is only locally systemic. It moves only from the top of the leaf to the underside of the leaf, or from the leaf stem to the leaf tip. It doesn’t move into the plant. As new leaves emerge, they won’t be protected. You have to continue to scout fields as plants grow to track disease development and progression.” — Andrew Friskop, NDSU Extension plant pathologist, cereal crops.

Controlling absinth wormwood
Question: How can I control absinth wormwood in a newer alfalfa/grass pasture or CRP planting without damaging the alfalfa?

Answer: “Milestone would be a good option through a spot spray application, but the alfalfa would also be injured if any spray landed on non-target plants. If the area is too large, then mowing if allowed in CRP will help reduce wormwood infestations.” — Rod Lym, NDSU weed science professor.

Two-week protection from blackleg
"Protection against blackleg offered by most canola seed treatments usually wears off approximately two weeks after emergence of the seedlings. After that, seedlings will be infected if inoculum is available and weather conditions are favorable. Scout fields for symptoms of infection starting on the second week after planting and continuing until the plants have passed the four-leaf stage. If blackleg symptoms are present in 20% or more of the seedlings, consider a fungicide application. Most fungicides registered to manage blackleg are more effective when applied at the two to four leaf stage. Fungicide applications made later will not control the pathogen effectively." — Sam Markell, NDSU Extension plant pathologist, broad-leaf crops.

Compiled from the North Dakota Crop and Pest Report.

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