If you live in central or southern Indiana, except for a few pockets in west-central, northeast and southwest Indiana, you may think all the talk about Palmer amaranth is overblown. But pictures don't do it justice. Once you've seen it, you will know why you ought to be watching your fields for it or taking preventive measures, even if you haven't seen it yet.
This isn't soybean rust, which created great hoopla and has yet to show up with any consequences in Indiana and most Midwest states. Palmer amaranth is here, present in at least one-fourth of Indiana counties, and is resistant to glyphosate.
Related: How To Identify Palmer Amaranth
"If it gets by you and is bigger than 4 inches, you just can't hardly bring it down postemergence," says Bill Johnson, Purdue University weed control specialist. Purdue has plots on Palmer amaranth in the far northeast corner of Cass County, near Twelve Mile.
It's likely not just a coincidence that a large dairy, Providence Farms, is located directly across the road from the plot. Many suspect it first arrived in cottonseed meal, at least at those locations. Palmer amaranth was a huge problem in the south, particularly in cotton, long before it showed up here.
"You really need some sort of program that includes residual herbicides, Johnson says. "We are evaluating different options. We can control it starting with residuals, but it takes a combination to give good control. We want to use at least two modes of action on it."
Some of the programs which control the weed fairly well cost as much as $60 per acre or more, not counting application costs. Once you have it, it isn't a cheap weed to fight, Johnson says.
One problem is that 95% control is not good enough. A few escapes can produce tens of thousands of seeds, and allow it to spread. Some farmers in northwest Indiana have already resorted to hiring crews late in the season to go through and remove individual plant escapes by hand to prevent them for shedding more seed on the soil.