As we begin this cool spring, wheat growers quickly will be faced with weed management decisions. This spring, the million dollar question could be, “Will my herbicides work in these cool temperatures?”
Stress conditions, whether they be moisture or temperature related, limit physiological processes in all plants, including weeds, to some degree. This can limit the response of weeds to herbicide applications. Adequate levels of control often can be achieved, but the slower activity of the herbicide application sometimes allows weeds to recover before the crop can out-compete them. The slower activity of the plants caused by cooler temperatures also might slow the metabolic process of the herbicide by the desired crop, resulting in crop injury.
So should you spray or wait for better weather? The number and size of the weeds, as well as weed species in the spectrum ultimately will determine this answer. If you feel you can wait a few days and still maintain adequate weed control and the weather looks to be warming, the logical choice is to wait.
Dr. Jim Martin, University of Kentucky Extension weed specialist, gives the following tips to consider as we progress through this spring:
n Harmony and Harmony Extra are examples of ALS- inhibitor herbicides that can injure wheat in cool, wet soil conditions. Injury also could occur if wide fluctuations of day and nighttime temperatures occur prior to, or soon after, application. It is not clear to what extent, if any, the injury observed for Harmony and Harmony Extra impacts wheat yield. The labels of these products recommend adding 2,4-D as a tank mix partner to limit the risk of injuring wheat from the ALS-inhibitor herbicides. It is important to recognize the safest time to use 2,4-D in wheat is when plants are fully tillered and prior to jointing.
n Some growers might be tempted to include Clarity, Banvel or other products with dicamba as a tankmix partner with other herbicides to enhance control of certain broadleaf weeds. Avoid using dicamba once wheat begins to joint to limit the risk of injuring wheat.
n When controlling wild garlic with Harmony, Harmony Extra or similar generic products, allow time for plants to develop 2 to 4 inches of actively growing tissue. The new growth emerges from the base of the plants and not from the old leaves that have tip burn from cold temperatures.
One final general note for this spring: With a colder-than-normal winter and cooler-than-normal temperatures so far in March, it appears we could have a slow start to spring.
Think about it: By the calendar, we’re less than two weeks away from planting corn. It sure hasn’t felt like corn-planting weather the last few days.
For more information about weed control in wheat, call the Hardin County Extension Service at 270-765-4121.
credit:thenewsenterprise.com