Managing Rust in 2016 Wheat Production
Over the past few days, several disease outbreaks in wheat have been noted by NCSU faculty and Extension. It is strongly advised to scout fields regularly. Some of these diseases can cause severe yield loss.
This disease is unusual for North Carolina. Symptoms include severe stunting, excessive tillering, some leathery leaves, and some yellowing of the plant. (See image below). Downy mildew is caused by the organism (Sclerophthora macrospora). This is an oomycete, not a true fungus. As such, spores are disseminated by water and plant parts in standing water are subject to infection. Infected plants are unlikely to form heads or seed, and many die before jointing. If a diseased plant does develop a seedhead, it will be twisted giving the disease its name “crazy top.”
Standing water is a major reason for the problem. At this growth stage (April 2016), nothing can be done for the current crop. Improving drainage in problem areas is a the solution. It may be advisable to avoid replanting wheat in fields with severe damage and to control grassy weeds, as they may serve as host plants. Grain to be used for seed should be thoroughly cleaned by fanning to remove all fragments of disease tissue and lightweight kernels, as the disease may be seedborne.
Low to medium levels of wheat stripe rust have been observed across the state over the past week. Current weather in North Carolina is ideal for stripe rust development and this disease can spread very fast. Unfortunately, there is no good comprehensive stripe rust ratings for North Carolina commercial varieties because this disease is fairly rare for this area.
Unusually early and high levels of leaf rust have been observed broadly across the Coastal Plain. The early severity is due to the warm winter. Leaf rust ratings for many, but not all, wheat varieties grown in North Carolina is found at (https://smallgrains.ces.ncsu.edu/).
Images of both leaf and stripe rust are below. Growers are advised to scout fields immediately and continue scouting through seed development. If significant infection is found and, if the field has good yield potential, treat immediately with a fungicide. (Note: It is more important to catch stripe rust early than to catch leaf rust early). Attached (below) is a table of effective fungicidal treatments. Please note that application of a strobilurin or strobilurin-containing product at flag leaf and later crop stages increases the likelihood of DON should scab develop.
Effective Fungicide Treatments: NCERA 184 Wheat fungicide table 2015_V3
For more information, visit the NCSU Small Grain Website
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