Orchard Weed Tips for Early Spring

What's happening with orchard weeds now?

• "Weed-free" strips under trees are sprouting many weeds!
• Annuals are germinating - pigweed, lamb's-quarters, groundsel, barnyard grass and foxtails are at cotyledon-stage.
• Winter annual rosettes are well established - flower stalks are bolting in Canada fleabane, peppergrass & buttercups.
• Perennial shoots are emerging from underground parts - Canada thistle, stinging nettle, and quackgrass have emerged.
• Flowers are now visible on dandelions, peppergrass, chickweed & groundsel.

How to scout for weeds in spring?

• A pane of glass pressed to the ground in the sun will let you observe the first flush of weeds. This should give advance notice for preemergence herbicides.
• Check closely for emerging annuals. Identify at the cotyledon to first true leaf stage. Annuals are usually fairly uniform across the fields.
• Mark field maps where patches of perennial weeds occur. Wait until susceptible stage for herbicide treatment: early bud for Canada thistle and sow-thistle, bud for milkweed, first flower for bindweed.

When to act?

• Scouting for weeds should be done weekly, or more frequently when temperatures are warm. Expect new germinations with each rain.
• Growers need to control weeds early. Remember that the critical weed-free period for bearing fruit trees is until 30 days past bloom. For new trees, May, June and early July are the most important times to be weed-free.

What control measures should be done now?

Growers usually use one of these control strategies:

• Apply a preemergent herbicide eg. Princep, Dual Magnum, before weeds emerge. A second application (including Gramoxone, glyphosate or Ignite) will be needed around mid-June as weed escapes begin.

• Wait until weeds have emerged (around mid-May). Apply a burndown + preemergent herbicide (not too late - remember the critical period!).

• Apply a mulch under trees before weeds emerge. 4-6" of mulch in needed.

OR

• Use mechanical means to destroy weeds under trees eg. flamers, cultivators, steamers, etc. These work better when weeds are small.