Risk Factors And Management Recommendations For Wheat Diseases In Nebraska

Aug 31, 2017

By Stephen Wegulo

Extension Plant Pathologist

Virus Diseases — Wheat streak mosaic virus / Triticum mosaic virus / High Plains virus / Wheat soilborne mosaic virus (Figure 1 )

Risk Factors

Pre-harvest volunteer wheat in wheat fields where there was pre-harvest hail
Pre-harvest volunteer wheat in summer crops such as sunflower
Grassy weeds, for example, barnyard grass, green foxtail
Prolonged warm fall/mild winter
Early planting
Planting wheat next to late maturing mite-virus hosts, for example, corn or foxtail millet
Planting into low, poorly drained ground (wheat soilborne mosaic)

Figure 1. Wheat streak mosaic in a grower’s field in the southern Panhandle of Nebraska in May 2012

Management

Control pre-harvest volunteer wheat in wheat fields and summer crops
Control post-harvest volunteer wheat
Control grassy weeds
Avoid planting wheat too early
Avoid planting wheat next to late maturing mite-virus hosts such as corn and foxtail millet
Avoid planting wheat in low, poorly drained fields or areas
Plant resistant/tolerant varieties if available and adapted to local conditions; most varieties are susceptible. See the Nebraska Fall Seed Guide and the K-State Wheat Variety Disease & Insect Ratings.
Plant high risk fields last, for example. fields adjacent to grassy weeds and late maturing corn or foxtail millet

Stripe Rust (Figure 2 )

Risk Factors

High inoculum load in southern states
Overwintering caused by a prolonged warm fall followed by a mild winter
Grassy weed hosts
Cool, wet spring

Management

Plant resistant varieties. See the Nebraska Fall Seed Guide, the K-State Wheat Variety Disease & Insect Ratings, and these CropWatch articles: Fall Strategies for Managing Wheat Diseases and 2017 Stripe Rust Ratings from Eastern Nebraska Wheat Variety Trials.
Wheat field with stripe rust

Figure 2. Stripe rust in a grower’s field in south central Nebraska in May 2010

Avoid planting wheat too early in the fall
Scout wheat fields starting early in the spring
Apply a fungicide in the spring; in a high risk situation – for example, stripe rust is detected early in the spring and there is a wet, cool spring – two sprays may be needed, one in early spring and a second one to protect the flag leaf. If only one spray is possible due to economics, the flag leaf spray is recommended
Do not spray for stripe rust in the fall; if you are unsure, have a UNL extension specialist look at your field before you take any management measure in the fall.

Fungal Leaf Spots — Tan spot, Septoria, spot blotch (Figure 3 )

Risk Factors

Wheat drilled into wheat stubble
Wet spring

Figure 3. Tan spot

Management

Crop rotation. Avoid drilling wheat into wheat stubble.
Scout wheat fields starting early in the spring.
Apply a fungicide in the spring; in a high risk situation – wheat drilled into wheat stubble and a wet spring – two sprays may be needed, one in early spring and a second one to protect the flag leaf. If only one spray is possible due to economics, the flag leaf spray is recommended.
Plant resistant/tolerant varieties if available and adapted to local conditions; most varieties are susceptible. See the Nebraska Fall Seed Guide and the K-State Wheat Variety Disease & Insect Ratings.

Fusarium Head Blight (FHB, scab, Figure 4)

Figure 4. Fusarium head blight

Risk Factors

Planting into corn, wheat or sorghum stubble
No-till or reduced tillage
Background spore inoculum in the atmosphere
Excessive and continuous rainfall before and during flowering
Irrigation
Moderate to warm spring temperatures
Susceptible cultivars

Management

Plant resistant/tolerant cultivars. See fusarium head blight ratings in CropWatch (Fall Strategies for Managing Wheat Diseases), and the K-State Wheat Variety Disease & Insect Ratings.
Plant several cultivars with different flowering dates.
Rotate wheat with non-host crops such as soybean or other broad leaf crops.
Avoid planting wheat after corn, wheat, or sorghum.
Manage irrigation in the spring and summer.
Apply a fungicide at flowering.

Seed-transmitted and soilborne fungal diseases — Common bunt, loose smut, flag smut, ergot, root and crown rot diseases (Figures 5 and 6)

Risk Factors

Planting bin-run seed – common bunt, loose smut, flag smut, ergot
Planting wheat after wheat
Planting wheat after grasses, for example, in ground that was under CRP
Planting in a poorly prepared seedbed
Planting in soil with insufficient or excessive moisture
Planting at an improper depth

Figure 5. Common bunt

Figure 6. Ergot

Management

Plant certified, fungicide-treated seed. Certified seed is variety-pure and free of contamination with weed seeds and pathogen propagules as ergot sclerotia. Fungicide seed treatment ensures microscopic fungal spores and mycelia are killed, which prevents infection during or after germination.
Avoid planting wheat after wheat or after CRP.
Plant in a well prepared, firm, mellow seedbed.
Avoid planting too shallow, too deep, or in soil with insufficient or excessive moisture.

Integrated Wheat Disease Management

The most effective strategy for managing wheat diseases is to combine as many management tactics as practical into an integrated disease management program. These tactics are:

Scouting and disease identification
Variety selection
Cultural practices
- Crop rotation
- Tillage and residue management
- Planting date
- Nutrient management
- Irrigation management
- Control of volunteer cereals and weeds
Chemical control
Biological control
Use of disease forecasting systems when available

Source: unl.edu