Just prior to harvest is a great time to assess your weed control successes and defeats. The successes are easier to determine – the fields remained clean and limited weed seed was produced. In defeats, this exercise can be more difficult to determine and may be due to several factors – read more below.

Identify the weed species that escaped.

• Should the species have been controlled by the herbicide program?
  • Some fields have significant Velvetleaf escapes, but the program did not include an herbicide that controls the weed. This is an easy fix, and an appropriate herbicide can be added to the program next year. Logistically, it would be great if one herbicide program controlled all the weeds in all our fields, but that may not be the case. Knowing what weed species are in each field can help customize herbicide programs and achieve better control.
• If the program should have controlled the species that escaped, dig deeper to determine the cause and ask yourself some questions.
  • Did Mother Nature interfere with the success of the application? Was the application delayed causing the weeds to be taller than the herbicide can effectively control? Did the field receive too little rain to activate the residual herbicide or too much rain that pushed the herbicide below the weed seed germination zone? Was it a cooler, cloudy day that negatively affected the success of a contact herbicide? Factors like this cannot be controlled, but it is important to know the herbicide was not at fault. Is the problem weed species showing signs of herbicide resistance? Illinois has several weed populations with documented resistance to herbicides. A switch in herbicide chemistry or implementation of non-chemical weed control measure may be needed.

Determine the best course of action for better weed control.

• If the weeds will interfere with harvest, consider a desiccation herbicide application. Timing of this application is very important to not decrease yield.
• Are the weeds present in the field biennials, perennials, or winter annuals? If so, consider a fall herbicide application. An herbicide application in the fall will move the herbicide into the underground storage organs and effectively control the species.
• Planting cover crops can reduce weeds if managed properly. The cover crop needs to be planted at enough density and be left to grow in the spring until it has enough biomass to serve as a mulch for the growing season. Cover crops require a higher level of management and should be researched before implementing.
• Initiate weed control strategies on a field by field basis for potential increased control.