Effects of excess rainfall, herbicide resistance addressed

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KIMBERLY

As the end of one of the best cropping seasons ever, area farmers weren't succeeding in finding buyers for their excess production and, by early August, were wondering if there were any risks in not taking the last one or even two cuttings of alfalfa, Outagamie County crops, soils, and horticulture agent Kevin Jarek reports.

Area farmers enjoyed per acre winter wheat yields of 90 to 125 bushels without having had to protect the crop with a fungicide along with excesses of oats and peas forage, haylage, and dry hay, Jarek told attendees at the semi-annual farm management update for ag professionals sponsored by Extension Service offices in east central Wisconsin counties.

(Jarek's observations about an abundance of crop production were reinforced by the more than a dozen listings in a crop insurance company's autumn newsletter by farmers looking to sell alfalfa and grass hay bales, wheat straw, and corn for silage. There was no listing by anyone looking to buy.)

Regarding the question about not taking late cuttings of alfalfa, Jarek's answer was that the risk of smothering was minimal unless there is a significant portion of grasses in the hay stand. One challenge with the 2016 alfalfa crop was having enough time between rains to make dry hay – a situation that led to having only 10 hay sample entries at the Outagamie County fair, he observed.

Corn crop concerns

Some mid to late season problems are cropping up with corn, Jarek noted. He cited early summer predictions by area crop consultants of possible corn grain yields of 240 to 260 bushels per acre – a number that's likely to be pared back because of ear tipback on kernels (one to two barren inches at the ends of ears) because of unfavorable weather during pollination, particularly with the corn hybrids having a maturity rating or 100 days or more.

With several heavy rains in early September, the risk of molds and mycotoxins in corn has risen, Jarek warned. Because those rains came at the start of the ideal period for harvesting corn for silage, farmers were faced with the tough choice of creating soil compaction in muddy fields or waiting to harvest until after the ideal window for making silage.

Jarek also shared some concerns about soybeans in the wake of heavy foliage growth and the late season rains. He said growers might suffer yield losses due to white mold infestations on up to 30 percent of plants and that lodging of the tall or thick foliage would lead to molds before harvest.

Corn silage pricing

For sellers and buyers still trying to establish a price for corn silage, Waupaca County agriculture agent Greg Blonde reminded attendees that the Extension Service has an Android app for pricing standing corn that free to users. It is available under the title “Corn Silage” on the Google Play Store.

Blonde, who played a major role in developing the app, explained that the table considers such factors as local corn prices, production costs, nutrient removal, expected yields, and even the potential of soil compaction during harvest. It provides all of the criteria for buyers and sellers to negotiate a fair price, he said. He reported app download totals of about 500 for corn silage and 650 for high moisture shelled corn.

Herbicide resistance

Whatever the crop yields and quality prove to be in a given year, an emerging problem in Wisconsin and well beyond is the development of resistance by weeds to herbicide ingredients, Door County agriculture agent Annie Deutsch reminded the program attendees.

Since 1979, there have been 13 weed species in Wisconsin for which resistance to at least one herbicide has been proven, Deutsch reported. Six counties in the state have incidents of resistance by water hemp to glyphosate (original trade name Round-Up) while two counties have confirmed resistance by Palmer amaranth to glyphosate, she noted.

Both of those weeds, members of the pigweed family, can cause large yield losses in both corn and soybeans because of competition during the growing season – not to mention the prolific seed production by both species, Deutsch pointed out. Water hemp grows rapidly and generates seed that is viable for up to four years, she indicated.

Incident diagnosis

Not all weed survival of a herbicide treatment is necessarily due to the weed's resistance to the product, Deutsch remarked. Failures could be due to the herbicide mix, the application rate, the size of the treated weeds, environmental conditions, or even dirt on the weed plant leaves at the time of application, she explained.

Crop growers who suspect that they have weeds with a herbicide resistance are asked to contact their home county Extension Service agriculture or crops agent to arrange a contact with the state-level specialists who are tracking this phenomenon, Deutsch advised.

Starting with seeds from suspicious weed plants, confirming a case of herbicide resistance takes about 1.5 years in facilities at the University of Wisconsin in Madison. For water hemp, the University of Illinois offers a rapid molecular test for a fee of $50.

Regardless of the situation, Deutsch said all crop growers applying herbicides should vary the modes of action from year to year, make both pre-emergent and post-emergent applications if necessary, strive for an early canopy by the crop, and avoid tillage and harvesting practices that would spread weed seeds between fields.

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