Now is the time of year when weed management decisions directly affect next year’s bottom line.

The plants that have escaped control measures and are still actively growing now, generate thousands to millions of seeds, depending on species and level of control. Even taking steps that reduce seed set, without completely killing the plant will make a big difference the following years; it’s really a numbers game with annual weeds. Imagine a kochia plant which can produce 50,000 seeds per plant. Achieving 70% control (many branches burned off with a PPO product like Flexstar or Cobra, but the central stem is still green and produces new branches) will reduce the weed seed bank to 15,000 potential progeny. That is still a lot of kochia, but the problem will be much more manageable. And of course, be looking for the reason plants may have escaped control measures. For instance, are they still surviving because they were too large when sprayed, or is it because there is a resistant population starting in the field?

Weeds to watch (7-18-14):

• Kochia: currently flowering and beginning to set seed

• Common Lambsquarters: many plants have already set some seed

• Redroot pigweed: early emergers have already have seed heads

• Green and yellow foxtail: just beginning to head out
  
  
• Nightshade: plants started emerging 14 days ago in some areas

A kochia control trial at the CREC.

Mike Ostlie
Agronomist