It's Time to Target Perennial Weeds in Orchards and Vineyards

June is the time to spend a few minutes scouting orchards and vineyards for perennial weeds, and spot treating them to prevent major problems.

Timing

Many broadleaf perennial weeds are just approaching the sensitive stage for systemic herbicides like glyphosate. For best results, apply at these stages:

• Canada Thistle @ early flower bud
  
• Milkweed @ flower bud
  
• Bindweed @ full flower
  

Quackgrass needs to be actively growing with at least 3 to 4 new leaves to absorb the herbicide. Often by June, it's too late to spray quackgrass, but if quackgrass is still growing, it's still susceptible.

Rates

The correct rate for each weed is listed on the label. For example, there are 3 rate ranges for glyphosate products:

• Annual weeds: 0.75 to 3.5 L/ha
  
• Canada thistle and quackgrass: 2.5 to 7.0 L/ha
  
• Perennial broadleaf weeds: 7 to 12 L/ha
  

Use the high end of the rate range where weeds are larger and growth is dense.

Caution

Avoid contacting desired plants, including low branches and root suckers. These herbicides circulate in trees for several years if absorbed. Some research suggests that low levels of glyphosate in a plant makes it susceptible to disease. Wick wipers will minimize contact with the crop, and shields can protect low hanging branches.

Prevention

Essential to succeed in controlling perennial weeds, especially in orchards and vineyards:

• Scout for weeds along the edges of fields, in fencerows and ditch banks.
  
• Prevent seeds by mowing or using a systemic herbicide before flowering.
  
• Clean up fields for new plantings by spot treating perennial weed patches.

Control of perennial weeds is generally a 2 or 3 year proposition. Investing some time each year will keep these pests to a manageable level in your orchards and vineyards.

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