Volunteer corn can be a significant problem in corn‐cotton rotations under no‐till and limited tillage. Volunteer corn can result from grain loss at harvest due to poorly adjusted combines, late season hail damage, hybrid selection with poor ear retention, and/or lodged corn plants that dropped corn.
If ear rots are present during the corn phase of the rotation, producers may opt to intentionally adjust the combine to discard low weight kernels during harvest. Lowweight kernels will over winter and may still be viable to germinate the following spring. In a cotton rotation, volunteer corn can become a significant challenge to the developing cotton crop.
Like all weeds, volunteer corn uses water and nutrients in addition to shading young cotton plants all of which causes a yield loss. Additionally, heavy volunteer corn can cause cotton harvest challenges.
Volunteer corn begins to germinate in conjunction with cotton germination. In instances when the ears are poorly shelled, kernels often do not germinate until irrigation is initiated for the cotton crop resulting in two flushes of volunteer corn. Because cotton is planted in May, there is not sufficient time to allow germination and termination of the volunteer corn prior to cotton planting.
There are few herbicide options for volunteer corn in cotton. Most cotton and corn varieties are glyphosate and/or glufosinate resistant. Planting stacked herbicide traits results in the inability to control volunteer corn in a cotton crop using either a glyphosate or glufosinate herbicide.
For producers who maintain a corn‐cotton rotation, ordering corn hybrids without the Liberty Link trait would provide the opportunity to spray Liberty (glufosinate) to easily control volunteer corn. However, in many cases planting decisions change due to markets and even weather so in‐season herbicide options must be evaluated.
Treflan (trifluralin) is a preemergent herbicide labeled for volunteer corn in cotton, but in the event of a cotton crop failure, northern Texas High Plains producers will restrict their plant back options if Treflan is used. In regions of Texas where irrigation plus precipitation is 20 inches or less, there is an 18‐month plant back to grain sorghum and a 5‐month plant back to corn.
A timely post emergent herbicide application is recommended when corn is between 5‐ and 12‐inches tall using a labeled herbicide with grass activity (Table 1). There are in‐season rotational restrictions for grain crops, but rotational restrictions will not carryover beyond into the following cropping season.
Post‐emergent herbicides are the most effective option in no‐till and limited‐tillage fields where pre‐emergent herbicides may not make soil contact and reach the germinating seedling.