Weed control easiest earlier in the season

Texas A&M University, 02/25/2013


Wheat in Terry and Yoakum counties in Texas varies from good condition to very poor. Some acceptable stands were established where irrigation has been adequate and germination was not delayed by blowing sand. Wind storms in January did significant damage to many area fields, with some being disked under to prevent further damage from blowing sand. Now is a good time to evaluate potential weed control measures, nitrogen fertility requirements and insect/mite infestations in wheat being carried to grain.

Winter wheat: weed control and fertilization

Many winter weeds are still small and in the rosette stage of growth. This is the easiest time to manage these weeds. If these weeds are actively growing and not stressed, lower use rates of herbicides will be effective; whereas once winter weed species bolt (begin upright growth and flowering) they will require increased herbicide usage rates in order to manage them. Marestail, redstem filaree (storksbill) and various mustards (London rocket, tansy mustard, etc) abound in some fields. With the recent moisture, these weeds will bolt and grow rapidly. Many herbicides labeled for use in wheat will control these small weeds. Consider herbicides with some residual control, depending on your rotational plan for the field. A detailed listing of weed control options in wheat is available here: http://lubbock.tamu.edu/files/2011/10/weedguideforwheat08_1.pdf.

Fertilization needs in winter wheat should also be evaluated at this time. Hopefully a soil test was collected and producers are following those recommendations. Approximately, one-third of one’s planned nitrogen should have been applied previously, a second third of that should be applied prior to jointing (stem elongation), which generally occurs approximately March 1 (however, jointing may occur up to two weeks earlier or later). I encourage you to evaluate the growth stage your fields are in. A guide to help identify wheat growth stages can be found here: http://lubbock.tamu.edu/files/2011/10/wheatgrowthstages_26.pdf Jointing describes the stage of growth where the wheat stems begin upright growth habit and is the initiation of the reproductive phase of growth. Nitrogen applied after jointing will have little impact on overall yield.

As a general rule of thumb, if one did not have a soil test, 1.2 lbs of nitrogen per bushel of yield is generally considered adequate. As mentioned now is the time to apply the second third of one’s total nitrogen, with the last third to be applied later in the season.

Irrigation of wheat is approaching a critical stage. While wheat has been growing vegetatively, it will soon begin stem elongation (jointing) and enter the reproductive growth phase. As the crop enters reproductive growth the water demand will increase rapidly. One should monitor soil moisture in order to keep pace with irrigation demand.

Brown wheat mite presence has been reported from Mr. Monti VanDiver, Extension Agent- IPM, Parmer and Bailey Counties. Now would also be a good time to scout for mites and greenbugs. Once one notices yellowing in the field due to insects, damage has occurred.




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