Pre-Seed Weed Control

Pre-seed weed control is a valuable tool to use in an overall weed control strategy for your crops. Early weed removal has been documented as an important step in maximizing crop yield due to reduced weed density and competition. Glyphosate has commonly been used in pre-seed weed control programs, however with the increasing concern for glyphosate-resistant weed development, growers should be actively utilizing multiple modes of action for their pre-seed programs. This strategy allows targeting weeds with two or more effective modes of action at once, which reduces selection pressure for resistant weeds and helps to manage herbicide resistance on the farm.

Pre-seed application is one of the easiest times to include a tank-mix into your herbicide program. Adding in a tank-mix partner to glyphosate not only expands the weed spectrum you can control, including volunteer glyphosate-tolerant canola, but can also add extended weed control with many of the new tank-mixes available. This will allow fields to stay clean longer and help to maximize yield.

Some of the excellent options for tank-mixing with glyphosate in a pre-seed program include:

1) Wheat, barley, oats – Intruvix (FMC), Korrex II and Paradigm (Corteva), Heat LQ (BASF), Blackhawk, Conquer II (Nufarm)
2) Spring wheat (not durum) – Inferno Duo and Inferno Trio (UPL), Focus (FMC)
3) Canola – Prospect (Corteva), Conquer II (Nufarm), Command Charge (FMC)
4) Soybeans and field peas – Heat LQ and Heat Complete (BASF), Valtera and Fierce (Nufarm), Authority, Authority Charge and Authority Supreme (FMC), Focus – soybeans only (FMC)
5) Dicamba-tolerant soybeans – XtendiMax (Bayer), Engenia (BASF), FeXapan (Corteva)
6) Field corn – Heat LQ and Heat Complete (BASF), Conquer II, Valtera and Fierce (Nufarm), Focus (FMC)
7) Flax and sunflowers – Authority and Authority Charge (FMC)

Rapid spread of glyphosate-resistant kochia in Manitoba – an analysis of kochia samples collected post-harvest in 2018 and compared to a similar study in 2013 revealed that the incidence of glyphosate resistance increased from 1 to 59% of kochia populations in Manitoba (Geddes et al). Of note, kochia collected from glyphosate-resistant crops such as soybean and corn had a greater percentage of resistant plants. The author of the study concluded that future “management programs will consist of increased reliance on alternative modes of action pre-emergence, adoption of herbicide-resistant crops with stacked resistance traits, and integration of non-chemical tools into current weed control strategies”.

The prudent use of add-in herbicides to glyphosate for pre-seed use will help curb the spread of glyphosate-resistant kochia and other weeds that could pose problems in the future. Remember to follow all the important tools in managing weed resistance such as using multiple modes of action, crop diversity, crop competitiveness, sanitation, as well as border and patch control. Get your suspicious weed escapes tested to know where your farm is at.

Please consult with your Shur-Gro agronomist to develop an effective pre-seed weed control strategy for your crops.