By Tom Collins
GUELPH — Vomitoxin made the headlines but there were plenty of other diseases, pests and problems that kept crop farmers busy in 2018.
Weeds, spider mites, Cercospora Leaf Blight, nitrogen loss and challenges with winter wheat establishment were all causes for headaches. Agronomists Melody Robinson, of Clark Agri-Service, and Chris Snip, of AGRIS Co-operative, were at the SouthWest Agricultural Conference at Ridgetown last month offering advice on how to stay on top of the issues this year.
1. Control weeds
The worst Ontario weeds last year were Canada fleabane, annual bluegrass and scentless chamomile, Robinson said. “The best weed control really comes from crop rotation and chemical rotation,” she said.
For Canada fleabane, a burndown like Eragon or Xtend technology was popular, while some growers used a combination of glyphosate and dicamba, she said. But after two years of use, weed populations of late-season fleabane, wild carrot, dandelions and late-season lambsquarters were more prevalent.
For annual bluegrass in soybeans, she recommended Focus or Fierce Zidura pre-emergence. In corn fields, she recommended Focus for pre-emergence and Atrazine or Acuron post-emergence.
For scentless chamomile, she said soybeans would need two burndown passes: One pass of glyphosate, and a second pass of glyphosate plus Eragon about one-to-two weeks later. With only one pass, the foliage fries off and the weed grows back due to its thick tap root, she said.
For scentless chamomile in corn fields, Robinson recommended GR 27 products (such as Callisto and Armezon), or Marksman or Atrazine.
Maximize soybean populations
Gaps in soybeans fields — sometimes due to poor emergence, or the planter dropping three or four seeds at once and leaving 18-inch gaps between plants — can affect yield, said Snip. Those gaps also allow more weeds to grow as there’s no competition for space.
To maximize soybean populations, Snip suggested maintaining the planter components within manufacturer specifications, planting into an even seedbed and having a good residual herbicide program. He also recommended assessing plant stands often in the early stages.
2. Control spider mites
Spider mites can cause soybean yield loss of 50 per cent, Robinson said. Control options are limited, as most aphicides don’t kill spider mites but do harm beneficials, she said, adding that controls can also be expensive, as high as $50 an acre.
If you’re unsure if you have spider mites, Robinson recommended a simple test. Take a piece of white paper into the field. Take a couple of soybean leaves, and sprinkle the leaves over the paper. You’ll see the spider mites moving around on the paper. Control is warranted if there is even one severely damaged leaflet per plant.
3. Control Cercospora Leaf Blight in soybeans
Ever notice bronze-coloured soybean leaves or purple seeds in your soybeans? That’s from the Cercospora Leaf Blight fungus, which can delay harvest and affect yield and quality. The fungal pathogen lives in dead plant material lying on the top of the soil, with infection occurring late in the growing season during the pod fill. Snip said farmers can incorporate the crop residue into the soil, but admitted that would be difficult to do on no-till farms.
Infection rate is higher during periods of warm temperatures with high humidity, so Snip recommended paying attention to the weather during pod fill.
If the fungus is a problem, Snip said farmers should choose more-tolerant varieties of seed, rotate with non-host crops and spray a fungicide if warranted (possibly a little later than you would normally spray).
4. Losing N
Robinson said farmers on heavy clay soils are most worried about losing Nitrogen via denitrification (where nitrates are broken down and released into the air). She pointed to a University of Nebraska study that said if the soil is saturated for five days, a farmer can lose 10 to 75 per cent of available nitrogen, depending on soil temperature.
She said farmers can manage the risk of nitrogen loss by using protected N products that have nitrogen inhibitors.
5. Winter wheat establishment
Seeding depth is critical, said Snip, adding that shallow seeding depth and hairpinning — where straw is pinned in the seeding slot — kills more wheat than frost. When in doubt, planting deeper is better, he said. “If you screw that up, you’re done.”
He also recommended controlling weeds before planting wheat. “We wouldn’t go and plant a corn or a soybean crop into a field that has a weedy mess,” he said. “Why are we planting a wheat crop into a weedy mess and expecting to control it the next spring?”
He also said for fertilizer treatment, phosphorus in-furrow is four times more efficient than broadcast.
Robinson recommended farmers spread out the risk of high-DON levels by planting multiple maturities. Choose a tolerant hybrid, but don’t give up on hybrids that yield well with a lower rating, she said. She also pointed out in the fields she saw, vomitoxin was worse where corn was stressed, so plant in good conditions, she said.
7. Volunteer corn
Farmers this year can expect an increase in volunteer corn (corn plants growing from seeds that were left in the field the previous year), Snip said. This is due to a late harvest (making for increased lodging and ear drop) and more fields destroyed because of high vomitoxin levels. In those fields, farmers need to choose this year’s crop and seed to account for controlling volunteer corn, he said. He also advised farmers to adjust their herbicide programs to include an effective method of volunteer corn control and to budget for volunteer corn control when crop budgeting.