Louisiana wheat disease management
Wheat is affected by several diseases that negatively impact yield if not properly managed. The major wheat diseases are leaf and stripe rust. In LSU AgCenter tests, rust-infested plots yielded more than 50 percent less than non-infested plots. This demonstrates the need to effectively manage these diseases to optimize profits. Other diseases that occur less frequently or are not as widespread are bacterial streak, stem rust, leaf and glume blotch, barley yellow dwarf, and head scab.
To minimize the impact of these diseases, an effective disease management strategy is critical. Therefore, LSU AgCenter scientists conduct research in an effort to develop effective management strategies. This is accomplished in part through assessing genetic disease resistance in varieties entered in the LSU AgCenter ‘Official Variety Tests’ (OVT). Standardized OVTs are conducted on several research stations every year. Each location represents a unique production area in the state.
In addition to variety testing, experimental and commercial fungicides, as well as application timings are evaluated for efficacy against the major diseases affecting Louisiana wheat. Data generated from this research is used to develop extension service recommendations. This information is also used in LSU AgCenter extension programming ef-forts across the state.
The first step toward an effective disease management strategy begins with proper disease identification. Diseases should be correctly identified in individual fields prior to applying a fungicide. It is important to know what symptoms are associated with each disease and the environmental conditions that favor disease establishment and spread.
Stripe rust development is most aggressive when temperatures are 50 to 65oF in the presence of intermittent rain or dews (6 to 8 hours). However, development can occur when temperatures range from near freezing to 70oF. Initial infections on seedling wheat may not have the characteristic striping pattern that occurs on older plants. Seedling infections often occur in ‘thumb-sized’ clusters on the leaves, as opposed to a random distribution that occurs with leaf rust.
Infections may appear as linear rows of small yellow to light orange pustules (stripes) on the lower leaves during late winter or early spring. Striped patterns are typical of infections in older pants. If conditions remain favorable for development, pustules may cover the entire upper leaf surface, as well as portions of the head. A lifecycle (infection to repro-duction) can be completed within 7 to 10 days under optimum conditions.