Disease Management in Cereal Crops

As I write this article the disease pressure in cereals has been quite minimal to date due to the cool conditions cereals have experienced so far. However, as temperatures begin to rise and canopies get thicker producers should be on the lookout for those important cereal diseases. Here are a few key diseases to watch for.

Powdery Mildew

Powery mildew is a disease that can cause issues in both wheat and barley. It likes lots of humidity as well as temperatures between 15-20°C. There have been some early reports of this disease in May in Huron and Perth counties. If the crop is at or approaching flag leaf, a fungicide application should be considered if the variety is susceptible and there are symptoms on the flag leaf and the second leaf (3-5%). If the forecast is for temperatures above 25°C and conditions are dry, a fungicide may not be necessary.

Septoria Leaf Spot

Septoria leaf spot is another early season disease in Ontario which thrives in prolonged wet conditions especially in May and early June. This disease can be controlled with timely fungicide applications. An application may be warranted if the variety is susceptible and if there are lesions on the second to last leaf up to the boot stage, or when there is a lesion on the flag leaf at head emergence.

Stripe Rust

Stripe rust (Figure 1) can impact wheat, rye and barley. It has been a disease that Ontario producers have experienced more in recent years. However, looking back on previous years when there were high levels of infection, the disease was found in Ontario early in May. To date the disease has not yet been identified here this year and we continue to monitor its movement south of the border. Stripe rust likes temperatures ranging from 12-21°C and can be identified by small yellow-orange lesions that merge to form stripes on the leaves of plants. Only in severe cases will it impact the head and VERY rarely does it effect the stems. Control of this disease is warranted when a susceptible variety is being grown, 1% of the flag leaf is affected and rainy, wet weather is in the forecast.

Figure 1. Stripe rust found in winter wheat. Stripe rust will not effect stems and leaf sheaths and only in severe infections will effect the head.

Figure 1. Stripe rust found in winter wheat. Stripe rust will not effect stems and leaf sheaths and only in severe infections will effect the head.

Crown Rust

Crown rust is the most important disease in Ontario oat production especially in southern Ontario (Figure 2). The main source of spores is from Buckthorn trees that are often found along field edges. The disease likes mild to warm temperatures (20-25°C) during the day and mild temperatures at night (15-20°C) with adequate moisture. Crown rust can also develop very quickly which is why it is so important to stay on top of scouting! In order to successfully manage this disease, tolerant varieties should be grown and fungicides need to be applied in a timely manner and close to flag leaf emergence.

Figure 2. Severe crown rust infection in a susceptible oat variety. Buckthorn is an alternative host to crown rust and should be removed from field edges if possible.

Figure 2. Severe crown rust infection in a susceptible oat variety. Buckthorn is an alternative host to crown rust and should be removed from field edges if possible.

Fusarium Head Blight

Fusarium Head Blight (FHB) (Figure 3) is still one of the most important diseases in cereal crop production effecting wheat, barley, oats and rye. Risk for FHB is greatest during wet, humid weather during the flowering period and when temperatures are in the range 22°C-27°C. Prolonged warm, wet conditions through to the end of the growing season can also increase the risk. Fields where cereals have been seeded following corn or other cereal crops are most at risk. To manage for this disease, moderately resistant varieties should be selected and a fungicide application made if the DONcast model is predicting high risk. To determine the risk of FHB infection in your field please check out the DONcast model which can be found at www.weathercentral.ca. Fungicide applications should be made on "Day 2". Day 0 occurs when 75% of the heads on the main stems are fully emerged. Day 2 is two days after this when anthers are visible on the middle of the wheat head (Figure 4).

Figure 3. Fusarium Head Blight infection in winter wheat can be identified by bleached heads or shrunken, wrinkled kernels.

Figure 3. Fusarium Head Blight infection in winter wheat can be identified by bleached heads or shrunken, wrinkled kernels.

Figure 4. Winter wheat head at Day 2, the optimum timing for a T3 fungicide application. Note the anthers, the pollen producing structures on the middle of the head.

Figure 4. Winter wheat head at Day 2, the optimum timing for a T3 fungicide application. Note the anthers, the pollen producing structures on the middle of the head.

For more information on fungicide selection please check out Publication 812, Field Crop Protection Guide, 2020-2021.

For more information on varietal disease tolerance please check out: GoCereals.ca.


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca