Taking an environmentally sensitive approach to pest management


Integrated Pest & Crop Management



AUTHOR

Kevin Bradley
University of Missouri
Division of Plant Sciences
(573) 882-4039
bradleyke@missouri.edu

At This Point, It's Mostly Just Revenge

Kevin Bradley
University of Missouri
(573) 882-4039
bradleyke@missouri.edu

Published: April 13, 2009

The most common questions I've received over the past week or so have to do with henbit infestations in wheat. My response has been the same in almost every instance, "That ship has sailed." Henbit is already in full bloom or past the full bloom stage in just about every part of the state. It is entering into its natural state of senescence and completing seed production. At this point, it will not be competitive enough with wheat to justify a herbicide application. Although Harmony Extra can be sprayed up to the flag leaf stage and will probably still control henbit, I do not think it is an economically justifiable treatment at this time. If there are other weeds like chickweed present, then you may want to reconsider but understand that henbit has already done all the damage it is going to do. The good news is that henbit is one of the weaker competitors as far as winter annual weeds go, and if you couple that with the fact that wheat is a very competitive crop, chances are you may not have lost yield anyway. For example, research conducted in Missouri has revealed that it takes as many as 82 henbit plants per square meter to cause even a 13% yield loss in wheat.

Herbicide applications are not necessarily warranted on henbit infestations like this that are in full bloom or past the full bloom stage of growth.

At this point in the season, it is also important to remember that applications of 2, 4-D must be made before the jointing stage of wheat or severe crop injury can occur. Jointing is a wheat stage that precedes stem elongation and can be determined by feeling the plant for the presence of a 'joint' just above the soil surface. You can do this by pinching the existing wheat stem and sliding your fingers upwards from the base of the plant. If a hard bump is felt about an inch or so above the soil surface, slicing into this area will more than likely reveal the presence of a joint, or node, and 2, 4-D applications should not be made.

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REVISED: October 2, 2015