Production Blog

Weeds Gone Wild

The pressure is on to get post sprays done before weeds get the edge. Increasing efficiencies in the field are one way to try to battle back against the weather. (DTN photo by Pamela Smith)

DECATUR, Ill. (DTN) -- The weeds in my garden almost got the best of me this spring. I relaxed for a couple of days. It was that "I'll get them tomorrow" moment that has been costing me since.

Given a reprieve from the hoe, the spiny amaranth (a gift that keeps on giving from some compost I incorporated several years ago) grew from a seedling to a stalk sent from Satan. The 3-inch rain shower we received this week made a mixed greens salad of weeds go wild. Even the rabbits are having a hard time finding my strawberry patch.

Farmers in my neck of the woods are feeling similar pressure. Wet weather and windy conditions have made for some tough post spray schedules. Fields in my regions of central Illinois definitely benefitted from the use of early residual herbicide programs. However, I started to see some weeds starting to break while walking fields this week. My email inbox started breaking loose with warnings about timely post spraying this week too.

South Dakota State University weed specialist Paul Johnson reminded growers in his weekly post that the era of delaying post sprays until all weeds have emerged are over -- especially when looking to prevent or manage glyphosate resistance. "When looking at help or control from conventional chemicals, the rule of thumb is 2- to 4-inch weeds, and it is best to err on the small side of that range," he writes. See more at: http://bit.ly/…

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Giant ragweed was the focus for the weed scientists from Purdue University. Giant ragweed sprouts early in the season and grows rapidly, blocking light from corn and soybean seedlings. Most manufacturers recommend applying post-emergent herbicide when giant ragweed is 4-6 inches tall.

"All too often we see where producers were reluctant to make post-emergent application to a 4-6 inch giant ragweed because of a lack of other weeds that size and the potential need for a second post-emergence application," said Bill Johnson and Travis Legleiter. "Waiting for other weeds to emerge or for the soybean canopy to further develop will only allow the giant ragweed to continue to grow well past a manageable height and likely affect yields." To read the full article, go to: http://bit.ly/…

I don't have any words of wisdom to outsmart this wacky weather other than to say, don't make the same mistake I did and wait. Weeds don't go on vacation. Consider that the growth rates for Palmer amaranth approach 3 inches per day. Yield losses of 78% (soybean) and 91% (corn) attributed to Palmer amaranth interference have been reported in the scientific literature.

What I am seeing is growers try to do whatever they can to increase efficiencies in the field. The homemade tender pictured above is a good example -- keeping that sprayer rolling across acres by having bulk chemicals at the field saves time (watch for more on this rig in another post).

Meanwhile, here's another good reminder about the need for timeliness and management. Recently, BASF created a time-lapse video that allows viewers to actually see how fast weeds grow in an untreated soybean plot compared to plots treated with popular herbicides. Take a look here: http://bit.ly/…

After watching, all I could think was: There goes my weekend.

Pamela Smith can be reached at Pamela.smith@dtn.com

(PS/AG)

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