Weather, Weeds Cause Trouble for Farmers

9/15/2012 7:00 AM
By Jane W. Graham Virginia Correspondent

Two of agriculture’s “W” words seem to have teamed up to make this summer of the unusual even more dramatic.

Weather and weeds are the team boggling the minds of farmers, gardeners and scientists.

Weeds seem not to be particular about how they partner with weather. If there is a lot of heat and moisture, they take advantage of the situation and zoom up to new heights and lengths, in the case of vines. If there is lots of heat and no moisture, they seek out bare spots and steal any available moisture and nutrients from less aggressive crops.

Scott Haegood, a weed specialist at Virginia Tech, said weeds have been growing inordinately fast in his part of the world around Blacksburg, Va.

He pointed to the record-breaking warm winter as giving weeds a head start in causing trouble for farmers, especially those using no-till planting methods.

Haegood said the winter annuals got a lot more growth earlier and caused more problems because it was harder to get a good no-till burn down in fields to be planted no-till.

Farmers using cover crops such as tillage radishes also ran into problems, he said, because there was no severe winter weather to freeze the radishes.

Weeds like Johnsongrass and bi-annual thistles were not killed or kept from growing by winter weather, with the result being the need for more weed control measures in the spring.

A drive down most any rural road that has not been mowed by the Virginia Department of Transportation makes it easy to see that the weeds, especially Johnsongrass, are taking advantage of the hot summer weather as well.

Chris Teutsch, an Extension forage researcher at Tech’s Southern Piedmont Agriculture Research and Extension Center, said weeds like open spots and grow where other crops have failed.

Virginia has not been alone in the outburst of weed growth. In Delaware, they have been on the warpath, too. Mark Van Gessel, a soil science professor and Extension specialist at the University of Delaware, said weeds have been a problem.

“Marestail/horseweed control was very difficult this spring due to plants being larger than normal with the mild winter,” Van Gessel said in an email.

“This year was very tough for post-emergence weed control in most crops because weeds were under drought stress at time of application,” he said. “As a result, we had lots of poor herbicide performance. I have seen lots of common lambsquarters in soybean fields this year.”

He reported seeing lots of perennials, as well, in fields that did not have many the past few years, particularly horsenettle.

Teutsch, who has worked extensively to find forage crops for livestock during Virginia’s usual droughty months, contends not all weeds are bad. He points to crabgrass as a prime example of a weed that has value for the livestock industry.

“Crabgrass is a good forage,” he said. “It grows quickly and feeds cows.”

Teutsch pointed to the message Kathy Voth, of Livestock for Landscapes, brought to the state’s forage industry earlier this year when she was keynote speaker at the Virginia Forage and Grassland Council’s winter conference.

The forage researcher, who uses livestock as a land management tool, told the attendees that cattle do eat weeds and in some cases the weeds have a higher nutritional value than grasses. She contended cattle can be taught to eat weeds.

Voth said her research has shown that some weeds are high in nutritional value. Some even have between 8 and 20 percent protein she said.

“In addition to increasing weight gain, high-protein plants can help animals take advantage of other low-quality forage, including pasture grasses that have begun to seed,” Voth said in a Lancaster Farming story published in January.

Another advantage of weeds is that they are available when grass is not for some reason, such as drought.

“During the drought of 1934-1939, Russian thistle provided a large part of the grazing for small ranches and farms,” Voth said. “It makes sense when you realize that digestibility is similar to other forages.”

Voth said herbicides aren’t working for farmers and ranchers who spend about $5 billion annually trying to eradicate weeds. In fact, weeds continue to increase by about 14 percent annually.

“The reason is the seed bank,” she said. “Every year weeds produce thousands of seeds and, depending on the weed, those seeds remain viable in the soil for 10 and even to 80 years. This means that weeds will always be with us.”

Not everyone sees weeds in a friendly light. In Delaware, two new weeds that have been spreading in that state are being targeted by the Delaware Department of Agriculture for control.

The weeds — Palmer amaranth and Texas panicum — have officially been placed on the state’s noxious weed list, which allows officials to begin educating landowners about the best ways to control them, the department announced recently.

“Our landowners can now get help to protect their properties from these invading weeds, the start of a solid defense against crop damage that will lower costs for farmers,” Delaware Secretary of Agriculture Ed Kee said in a press release.

The new weeds have been problems in the South, but are relatively new to Delaware. Texas panicum grows rapidly and emerges throughout the growing season; Palmer amaranth takes nutrients and moisture from crops and makes harvesting difficult. Palmer amaranth has also become resistant to certain herbicides.

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