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Pest Patrol: Manage volunteer corn in your 2019 soybeans

#PestPatrol with Mike Cowbrough, OMAFRA

Q: Due to a challenging 2018 corn harvest, I’ll likely be looking at more volunteer corn in my 2019 soybean crop. What suggestions do you have for managing this weed?

A: The only option to control volunteer corn in soybeans is to use one of the post-emergence herbicides from the Group 1 mode of action. If you wait until every last volunteer corn plant is emerged, not only will this negatively affect soybean yield, but you will end up targeting plants that are much too big to be controlled.

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Volunteer plants from Roundup Ready and Liberty Link corn hybrids are easily controlled by a number of herbicides provided they are applied prior to the six-leaf stage (Table 1 below). With high population densities you will often see a prolonged emergence period and likely the need to apply Group 1 herbicides twice to ensure the largest volunteers are no bigger than the six-leaf stage. It is important to note that volunteer plants from Enlist corn hybrids are not controlled by Assure II and Venture L. Therefore, herbicides that contain the active ingredient “clethodim” (i.e. Select, Statue or Arrow All-In) should be used instead (Table 1).

Xtend soybeans – Antagonism and reduced levels of volunteer-corn control can result when tank mixing volunteer corn herbicides with dicamba (i.e. Engenia, FeXapan or Xtendimax). Rates of the volunteer corn herbicide should be increased to overcome this antagonism if tank mixing (Table 2 below).

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