For Release September 21, 1999

A Weedy Summer

by Chuck Otte, Geary County Extension Agent

Every growing season seems to have it’s own personality. Either the weather, insects, weeds, or diseases seem to take prominence to give that particular summer it’s own unique feel. It looks like 1999 will be the summer of the weeds.

We know that every year we will have weed problems in our crop fields. That’s why herbicides are a billion dollar ag industry. But herbicides have limitations. Sometimes they work real well, other times they don’t work very well at all. Then in some years we have weed problems show up that we couldn’t anticipate or we couldn’t really do anything about anyway.

For herbicides to work most effectively, they need to be applied at the right time and with the right combination of weather conditions. The wrong weather at the wrong time can reduce the herbicide to a useless, but expensive, chemical. Too much rain after application can just break the herbicide down and wash it away. Too little rain after application and the herbicide just sits on the soil surface to be degraded by ultraviolet light. If the temperature goes too high or too low after application the product may not work or you may wind up with serious crop injury.

Changes in farming practices, types of tillage and herbicides can have amazing impacts on the kinds of weeds that we are fighting. Herbicides are formulated to deal with the worst weed problems in crop production. The worst weeds are going to cost the most dollars in the long run and have the biggest opportunity to provide profit to a herbicide company. If you constantly have spring tillage you are going to favor weeds that sprout in late spring and produce seed in the late summer. If you constantly have early fall tillage you will favor weeds that germinate in mid to late fall and produce seed in the spring.

The combination of no or reduced till and some of the "new" chemistry herbicides have created some major shifts in our crop fields. All of a sudden tree seedlings are becoming a real problem, and low rates of Roundup aren’t very effective against tree seedlings. Some of the old fashioned herbicides controlled a weed called Hop-hornbeam. But the new chemistry, low dosage herbicides seem to overlook this weed. All of a sudden it’s everywhere. Marestail or horseweed was a not uncommon weed, but seldom a problem in conventionally tilled fields. Put a field into no-till and you’ll see a lot of it.

We had a combination of everything this year. But the real tale teller was the eight weeks of cool wet weather in the late spring and early summer. This was just what we needed to get a lot of seed sprouted and growing. Then a quick turn, or rather periodic quick turns to hot and dry weather stressed a lot of our crops and pastures. The funny thing about hot dry weather is that it doesn’t tend to stress the weeds as much as it does the crops. That’s probably one of the reasons that they are weeds.

Alfalfa fields and brome fields seem overflowing with foxtail and crabgrass this year. There’s not much we can do now, and a normal spring will help. A little tweaking of management and perhaps a little herbicide can help next year. Every pasture seems loaded with Western ragweed. Here’s a perennial that’s around every year, but this year it’s real prominent. Sometimes it’s a sign of overgrazing, sometimes it’s just the year. If it stays a problem you may need to spray. Everyone had weed problems this year. Take notes in a notebook to help you plan next year. You may have to make some changes next year, or you may just mark it down as one of those weedy summers!


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