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Ascochyta

Overview

Ascochyta is a fungal disease that can affect various crops across Canada, including pulses, like peas, lentils, and chickpeas; alfalfa; and fava beans (also known as broad beans). 

Ascochyta can also impact international trade of affected crops. Countries may have regulations and restrictions on the import and export of crops that are susceptible to Ascochyta, particularly if the disease is prevalent or poses a significant risk to local production.

(Image credit: Mary Burrows, Montana State University, Bugwood.org)

How to Manage Ascochyta

How to Identify Ascochyta

The symptoms and signs of Ascochyta can vary depending on the crop species, variety, and environmental conditions. Additionally, other diseases or abiotic factors can cause similar symptoms, so accurate diagnosis is crucial. 

1. Leaf Spots 

Ascochyta infections often result in the development of small circular or irregular-shaped spots on the leaves of affected plants. These spots may vary in color, ranging from tan to brown or even black. They may coalesce to form larger lesions.

2. Stem Lesions

Ascochyta can cause lesions on the stems of infected plants. These lesions may appear as dark, sunken areas on the stem surface. They can be elongated or irregular in shape and may extend along the stem, leading to weakening and potential breakage.

3. Pod Infections

In crops that produce pods, such as peas, chickpeas, and beans, Ascochyta can infect the pods as well. Infected pods may develop lesions or discoloration, and in severe cases, they can show signs of rot. This can result in damaged or shriveled seeds within the pods.

4. Defoliation

Ascochyta infections can cause defoliation, especially when leaf spots become extensive and coalesce. Severe defoliation can lead to reduced photosynthetic capacity and overall plant vigor.

5. Spore Production

Ascochyta may produce spores, which can be observed as tiny dark-colored structures on the surface of infected plant tissues. These spores can be visible to the naked eye or may require the use of a hand lens or microscope for closer examination.

Geographic Impact of Ascochyta

It's important for farmers in Canada to be aware of the potential presence of Ascochyta in their specific regions and crops. The presence and severity of Ascochyta can vary within provinces and regions due to differences in climate, cropping systems, and disease management practices. Local conditions, including temperature, humidity, and rainfall patterns, can influence the prevalence and impact of Ascochyta in specific areas.

Pulse-Growing Regions 

The following pulse-growing regions of Canada may be impacted by Ascochyta:

  • Saskatchewan

  • Alberta

  • Manitoba

  • Parts of British Columbia 

Alfalfa-Growing Regions

The following alfalfa-growing regions of Canada may be impacted by Ascochyta:

  • Ontario

  • Quebec

  • Parts of the Prairie provinces

Fava Bean-Growing Regions

The following fava bean-growing regions of Canada may be impacted by Ascochyta:

  • Alberta

  • Saskatchewan

  • Manitoba

However, the Prairie provinces are known for their relatively dry climates, which may help reduce the incidence of Ascochyta blight compared to areas of the world with more humid conditions.

Ascochyta Around the World

Ascochyta is a widespread fungal pathogen that can be found in many regions across the globe. The specific geographic impact of Ascochyta can vary depending on several factors, including climate, cropping systems, and the presence of suitable host plants. 

It affects crops in both temperate and subtropical regions. Regions with cool and moist conditions during the growing season may be more prone to Ascochyta outbreaks. These regions may have a more significant economic impact from Ascochyta-related yield losses and reduced crop quality.

Timing of Ascochyta Emergence

The timing of Ascochyta infections can vary depending on the specific crop, environmental conditions, and the region where it occurs. In many cases, Ascochyta infections can occur early in the growing season. This is especially true for crops like peas, lentils, and chickpeas, where seed-borne or soil-borne inoculum can lead to infections during germination and early plant development stages.

Ascochyta infections can continue to occur throughout the growing season, especially if conditions remain conducive for disease development. This can include periods of cool and wet weather, which can promote the spread and severity of the disease.

In some cases, Ascochyta infections can persist until the harvest period, particularly if the disease is not effectively managed. This can result in reduced crop quality and yield losses.

How Ascochyta Impacts Crops

Ascochyta can cause significant yield losses in affected crops. The severity of yield reduction depends on various factors, including:

  • Crop type

  • Susceptibility of the variety

  • Environmental conditions

  • Disease management practices

As well, Ascochyta-infected crops may experience a decline in quality attributes. 

How to Manage Ascochyta in Crops

Regularly monitor your crops for signs and symptoms of Ascochyta as early detection is crucial for effective management. Scouting fields and assessing disease severity can help determine the need for fungicide applications.

Managing Ascochyta effectively involves a combination of cultural practices, crop rotation, and fungicide applications. The specific management practices may vary depending on the crop, region, and local recommendations. 

Resistant Varieties

Planting resistant or tolerant varieties is an effective way to manage Ascochyta. Look for varieties that have been specifically bred for resistance to Ascochyta blight. These varieties can significantly reduce disease severity and yield losses.

Seed Treatment 

Seed treatments containing fungicides specific to Ascochyta can provide early protection during germination and early growth stages.

Fungicide Applications

Fungicides can be applied during the growing season to manage Ascochyta. Some products containing boscalid and pyraclostrobin are labeled for use on Ascochyta. Timing and frequency of applications will depend on the specific crop, disease pressure, and local recommendations. Continue reading below for fungicide recommendations. 

Crop Rotation 

Implementing a diverse crop rotation plan can help break the disease cycle. Avoid planting susceptible crops in consecutive years, especially within the same field. Rotating with non-host crops can reduce the inoculum levels in the soil.

Sanitation

Practicing good sanitation measures can also help reduce the spread of Ascochyta. Remove and destroy infected plant debris, as it can serve as a source of inoculum for future infections. Also, clean and disinfect equipment and tools to prevent the transfer of the pathogen.

Irrigation Management

Avoid overhead irrigation methods that promote prolonged leaf wetness, as this can create favorable conditions for Ascochyta development. Opt instead for drip or furrow irrigation systems that minimize leaf wetness.

How Ascochyta Impacts Pulses

Ascochyta blight is a significant concern for pea, chickpea, and lentil growers. It can lead to discoloration, shriveled seeds, and reduced nutritional value. 

How to Manage Ascochyta in Pulses

Fungicides may be necessary to control Ascochyta. However, it's important to note that not all fungicides are labeled for use on legumes for Ascochyta. There are some products containing bacillus amyloliquefaciens strain f727 cells and spent fermentation media that are labeled for use with legumes for Ascochyta control. 

Fungicides for Managing Ascochyta in Chickpeas

FBN Prothio 480 SC

  • Timing: Apply FBN Prothio 480 SC VP at the first sign of disease. A maximum of 1260 mL/ha of this fungicide may be applied per year for chickpeas. There should be a maximum of three applications per year.

  • Rate: Apply FBN Prothio 480 SC VP at 315–420 mL/ha (150-200 g a.i./ha). After the initial application, repeat applications may be made at 10–14-day intervals. Apply the higher rate when conditions favour disease development or when growing less disease-resistant varieties.

Preach Fungicide

  • Timing: Apply Preach Fungicide and LANCE WDG Fungicide as specified at the beginning of flowering or at the onset of symptoms for the more aggressive diseases. Ascochyta blight in chickpeas develops quickly once established so early detection is essential to the success of any fungicide program. Do not apply sequential applications of this tank mixture combination. Alternate to a fungicide with a mode of action other than Group 7 and 11 for at least one application. If disease conditions persist or weather conditions are favourable for disease development, apply another application of Preach Fungicide tank mixed with LANCE WDG Fungicide. 

  • Rate: Preach Fungicide must be tank mixed at a rate of 0.40–0.60 L/ha with LANCE® WDG Fungicide at labelled rates. Do not apply by pivot or sprinkler irrigation.

Fungicides for Managing Ascochyta in Lentils

FBN Prothio 480 SC VP

  • Timing: Apply FBN Prothio 480 SC VP at the beginning of flowering or at the first sign of disease. A maximum of 840 mL/ha of FBN Prothio 480 SC may be applied per year for lentils. There should be a maximum of two applications per year.

  • Rate: Apply FBN Prothio 480 SC at 315–420 mL/ha (150-200 g a.i./ha). After the initial application, one additional application may be made 10–14 days afterward if conditions remain favourable for continued or increased disease development. Apply the higher rate when conditions favour disease development or when growing less disease-resistant varieties.

Preach Fungicide

  • Timing: Apply at the beginning of flowering or at the onset of symptoms for the more aggressive diseases. If disease persists or weather conditions are favourable for disease development, apply a second time 10–14 days later, alternating with a fungicide that contains a different mode of action.

  • Rate: 0.4 L/ha

Fungicides for Managing Ascochyta in Dried Shell Peas and Beans in Crop Group 6C

Azoxystrobin 250 VP

  • Timing: For Ascochyta blight, the first application must be applied before disease is established and no later than the onset of flowering. A second application can be made 10–14 days after the first application, when disease pressure is severe or when agronomic or weather conditions are conducive to disease development or movement.

  • Rate: 500 mL/ha

How Ascochyta Impacts Alfalfa

Ascochyta leaf spot is a common disease in alfalfa across Canada. It can cause leaf lesions, defoliation, and reduced forage quality.

How to Manage Ascochyta in Alfalfa

Managing Ascochyta in alfalfa can be challenging, but there are several strategies that Canadian farmers can employ to minimize its impact. Planting Ascochyta-resistant alfalfa varieties can help reduce the risk of infection. 

For black stem and leaf spot, the following may be effective: 

  • Crop rotation

  • Certified seed

  • Disease-resistant cultivars

  • Early harvest

  • Pyraclostrobin and boscalid fungicides 

Fungicides for Managing Ascochyta in Alfalfa

Preach Fungicide

Alfalfa grown for seed production may benefit from a fungicide application that contains pyraclostrobin to manage leaf spot (Ascochyta medicaginicola).

  • Timing: For optimal disease control, apply Preach Fungicide at the beginning of flowering (10–30% bloom) or the onset of disease. Do not make more than one application per year.

  • Rate: 0.4 L/ha 

Shaft Fungicide

Alfalfa grown for seed production may benefit from a fungicide application that contains boscalid to manage spring black stem (Ascochyta medicaginicola). 

  • Timing: Apply Shaft Fungicide at 20–50% flowering to control spring black stem. Apply every 7–14 days if disease persists or if weather conditions are favourable for disease development.

  • Rate: 420 g/ha

How Ascochyta Impacts Fava Beans

Ascochyta blight can affect various types of beans, including lima beans and fava beans. It can cause leaf spots, stem lesions, and pod infections, leading to yield reduction.

How to Manage Ascochyta in Fava Beans

Farmers in Canada can manage Ascochyta in fava beans by using products containing:

  • Azoxystrobin, such as Azoxystrobin 250 VP

    • Timing: The first application must be applied before disease is established and no later than the onset of flowering. A second application can be made 10–14 days after the first application, when disease pressure is severe or when agronomic or weather conditions are conducive to disease development or movement.

    • Rate: 500 mL/ha

  • Pyraclostrobin, such as Preach Fungicide

    • Timing: Apply Preach Fungicide at the beginning of flowering or at the onset of symptoms for the more aggressive diseases (e.g. anthracnose in lentils). If disease persists or weather conditions are favourable for disease development, apply a second time 10–14 days later, alternating with a fungicide that contains a different mode of action.

    • Rate: 0.4 L/ha

A fungicide should be applied to protect healthy plant material if disease inoculum is present and weather conditions favour disease development. Fungicides are most effective when applied at the beginning of flowering or the onset of symptoms. Usually, one well-timed application is sufficient for controlling Ascochyta blight in fava beans.

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Every product that labels ASCOCHYTA as a weed, pest, or disease the product can be applied against is shown below. Click any product for label and more information.
Ace™ 3.8L STBravo Weather Stik®Bravo Weather Stik®Bumper® ESCarb-O-Nator®Chloronil® 720Chlorothalonil 720Dexter™ MaxDexter™ XCELDisarm® G FungicideEluvium™Equus® 720 SSTEquus® 720 SSTFitness® FungicideFortuna™ 75 WDG FungicideInitiate® 720 Flowable FungicideManzate® Pro-Stick™ T&OMertect® 340-FMiravis® TopNufarm T-Methyl SPC 50 WSB FungicideObvius® Fungicide Seed TreatmentObvius® Plus Fungicide Seed TreatmentOmni® Brand Chlorothalonil 720SCOranil™ 6LOxiDate® 5.0Periapt™Praiz® NGPraiz™Procon-Z™ FungicidePropicon ECPulse Premix 4L STRancona® 3.8 FSRancona® CTSRancona® SummitRancona® V 100 Pro FSRancona® V 100 Pro FSRialto™ 720 FSlant™Slant™ ECStamina® fungicide seed treatmentSystiva® XS Xemium® Brand FungicideThiabendazole 4L STVibrance® MaxxVibrance® Trio