Wheat talk

Diseases, new research among topics at plot tours

As the 2017 wheat harvest gets under way, and the annual series of wheat variety field tours fades into the past, the major discussion topics have been a pair of diseases and research into updating recommendations for optimal planting dates.

Wheat plot tours in late June included stops in Cheyenne, Box Butte, and Kimball counties. The plots included older varieties, varieties that are currently widely grown in the area, and experimental lines that might become commercially available in future years.

Dipak Santra, alternative crops breeding specialist at the UNL Panhandle Research and Extension Center, said the tours included new experimental lines from both public breeding programs (UNL and Colorado State University) and private companies, including Lima Grain Cereals Sciences, WestBred (of Monsanto), and AgriPro (of Syngenta).

Santra said a pair of wheat diseases were the major topics of discussion.

Wheat streak mosaic (WSM) virus is prominent throughout the region. Three lines in the variety trials have genetic resistance to WSM via the registered genes WSM1 and WSM2. There are three viruses in the WSM complex: Wheat Streak virus, Triticum mosaic virus, and High Plains mosaic virus. Santra said neither gene provides high resistance to all viruses dominant in the region. The main control method recommended to combat WSM is controlling volunteer wheat to minimize the ability of the virus to survive until the following season.

Several varieties with some resistance have come from breeding labs at UNL and the U.S. Department of Agriculture’s Agricultural Research Service (USDA-ARS) at Lincoln.

Stripe rust is the other disease affecting western Nebraska wheat growers. Stripe rust is relatively new to this area, but already established. This year it appeared late in the season, at the end of May, but infestations were heavy in Cheyenne and Morrill counties, in the Dalton, Gurley and Sidney areas. Some stripe rust also was seen in Banner County.

This year stripe rust appeared when the wheat reached the flag leaf stage, so most of the foliar damage occurred to the plants’ flag leaf. This is likely to reduce yields, and seed quality is significantly reduced.

According to Santra, several varieties in the trial are resistant to stripe rust, including one UNL line and several private lines. He said the best approach to fighting stripe rust appears to be genetics and spraying where there are outbreaks.

Another common topic of discussion has been updating Nebraska Extension’s recommendation for optimal date of planting, based on elevation. The existing recommendation is almost 40 years old, and needs to be updated considering climate change. A regional trial is being conducted to update the planting date recommendation.

Another dimension being added to the planting date study is seeding rates. The importance of plant population per acre was emphasized in a couple tours, in order to take advantage of good genetics.

Seeding rate is important, Santra explained, because conventional seeding rates are based on pounds per acre, but there is a significant difference in seed size among new varieties, so the number of seeds per pound of large-seeded varieties is significantly lower than small-seeded varieties. So it’s important to consider seed size when calculating seeding rate.

Seeding rate and the importance of basing the rate on seeds per acre, as opposed to pounds or bushels per acre, is discussed in a NebGuide written by Santra and retired Crop Physiologist Alexander Pavlista, “Planting Winter Wheat in Dry Soil” (G2211). This publication is online at http://extensionpubs.unl.edu/publication/9000016368966/planting-winter-wheat-in-dry-soil/.

Another topic of discussion at the plot tours was weed management. New chemicals are being tested for managing difficult weeds such as feral rye.

There were several topics specific to irrigated wheat. The need to spray fungicide was stressed by UNL Extension Plant Pathologist Stephen Wegulo to protect against foliar diseases. And growers were urged to consider plant height and lodging susceptibility when selected varieties for irrigated fields. Too-tall varieties tend to lodge under irrigation. Medium height varieties with susceptibility also are not a good choice. Santra said the best choice is medium height varieties with lodging tolerance.