Early blight is one of the most widespread and destructive diseases affecting potato crops worldwide This fungal disease is caused by the pathogen Alternaria solani and can lead to severe defoliation and significant yield losses if left uncontrolled In this article, we will dive deep into early blight disease to understand its symptoms, life cycle, spread, and most importantly, how to effectively manage it.
What Exactly is Early Blight Disease?
Early blight, caused by the fungus Alternaria solani, is a foliar disease that attacks leaves, stems and tubers of potatoes. It is found wherever potatoes are grown but thrives in areas with warm, humid conditions.
The disease first appears as small, dark brown to black lesions on older leaves near the bottom of potato plants. These round or irregular spots enlarge into brown targets or “bull’s eye” shaped lesions about 1/4 to 1/2 inch in diameter, often marked with concentric rings.
As the spots increase in number and size, affected leaves yellow and die off. Entire plants can be rapidly defoliated, appearing scorched and dried up Stem lesions are also possible, with elongated black sunken areas that crack Tubers can become infected through wounds, developing brown, leathery patches of dry rot.
Recognizing the Symptoms
Detecting early blight promptly is crucial for effective management. Here are the telltale signs to look out for when scouting potato fields:
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Small dark brown to black spots on lower older leaves
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Spots enlarge into 1/4 to 1/2 inch brown target-shaped lesions circled with rings
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Dead brown areas around lesions surrounded by yellowing
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Severe defoliation of plants as disease progresses
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Elongated dark sunken lesions on stems
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Dry, brown rotting spots on potato tuber surfaces
The Early Blight Disease Cycle
To stop early blight, you need to know how it gets around and stays alive between growing seasons:
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The fungus overwinters as spores in crop debris and soil. It can also survive on infected seed tubers.
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In spring, spores are splashed onto lower leaves or shoots touch contaminated soil, initiating infections.
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7-14 days after infection, lesions develop and produce more spores.
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Wind, rain, insects, machinery spread spores to new plants.
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Lower leaves are infected first, with disease moving up the plants over season.
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Tubers become infected through eyes, cuts or wounds at harvest.
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The cycle repeats as the pathogen survives winter in debris.
Why Early Blight Disease is so Destructive
When early blight strikes a type of potato that is easily infected and the weather is good, the results can be terrible:
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Premature defoliation reduces photosynthesis and weakens plants.
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Smaller, fewer tubers are produced lowering yield significantly.
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Sunscalding of exposed tubers degrades quality.
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Infected seed tubers have poor emergence and vigor.
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Tuber infections reduce storability and marketability.
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Entire crops can be destroyed resulting in 100% yield loss.
Managing Early Blight Disease in Potato
Even though it’s hard to keep pests under control, an integrated pest management plan with many parts can help reduce early blight damage:
Cultural Practices:
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Plant resistant varieties – ‘Elba’, ‘Pike’, ‘Rosa’, etc.
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Use certified disease-free seed.
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Follow 2-3 year crop rotations with non-hosts.
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Eliminate cull piles and volunteer potatoes.
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Allow for adequate soil fertility and plant nutrition.
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Avoid excess nitrogen.
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Use drip irrigation and avoid wetting foliage.
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Hill soil around stems to prevent splash dispersal.
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Increase spacing for airflow.
Monitoring:
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Scout fields weekly looking for symptoms.
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Dig up plants to check tubers for infections.
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Keep records to track disease development.
Chemical Control:
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Apply protective fungicides like chlorothalonil, mancozeb, or Qol’s preventively.
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Start applications at first disease signs and reapply every 7-14 days.
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Rotate fungicide classes to avoid resistance.
Organic Options:
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Spray certified organic copper products.
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Apply biological fungicides with Bacillus subtilis.
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Improve plant health with compost teas.
The Key to Beating Early Blight
Early signs of blight can be scary because it can quickly spread and kill a lot of trees. But with careful inspection, early diagnosis, cultural practices that lower disease pressure, and targeted fungicide sprays, even varieties that are very likely to get diseases can still produce good yields.
The most critical factors are planting resistant varieties when available, practicing crop rotation, maintaining general plant health, and taking action at the first disease signs. Integrating multiple tactics provides the best early blight control and can hold this destructive pathogen at bay.
Now that you understand the early blight disease cycle and impacts, you can craft a robust management plan suited for your potato fields. Pay close attention to weather patterns, scout regularly, and be prepared to respond promptly at the first spots. With proper control measures, early blight does not have to mean devastating losses.
Managing early blight in the home garden Early blight lesions on tomato leaves
Early blight-resistant varieties are readily available. As early blight occurs commonly in Minnesota, gardeners should look into these varieties.
It doesn’t mean that there won’t be any early blight; it just means that resistant varieties can handle the pathogens better, so the damage will be less severe than with non-resistant varieties.
Cornell University keeps track of varieties sold as having disease resistance. You can often find this information in seed catalogs.
- Use fabric, straw, plastic mulch, or dried leaves as mulch to cover the soil under the plants.
- You can water each plant carefully by hand, with drip irrigation, a soaker hose, or a soaker hose.
- Stake or trellis plants to let more air flow through, get rid of weeds, and make sure plants are far enough apart.
- Cutting off the bottom leaves can also stop early blight spores from splashing onto the leaves from the ground.
- After two years, you can plant peppers or tomatoes in the same spot.
Biology Early blight starts at the bottom of the plant.
- Two species that are very similar can cause early blight: Alternaria tomatophila and Alternaria solani.
- It is possible for both pathogens to infect peppers, tomatoes, potatoes, and weeds in the Solanaceae family, such as black nightshade (Solanum ptycanthum) and hairy nightshade (Solanum physalifolium).
- Disease grows in temperatures between 59 and 80 F; 82 to 86 F is the best temperature range for it.
- It is most likely for the pathogen to spread when it is wet or when there is a lot of dew or when the relative humidity is 90% or higher.
- In Minnesota, the early blight pathogens spend the winter in both infected plant debris and soil. The pathogen can also live on tomato seeds or be brought in on tomato transplants.
- Lower leaves get sick when they touch contaminated soil, either directly or when raindrops splash soil on the leaves. Spores, which are reproductive structures, can grow between 247 and 90 degrees Fahrenheit and need free water or a relative humidity of 90 percent or higher. Plants get spores, which in just five days make leaf spots as small as 1/8 inch across.
- Spores can be spread across a field by wind, people, or tools, so there are many chances for reinfection during the growing season.
Blight: 5 Ways to Control Potato Blight (Late Blight)
FAQ
How do you treat early blight in potatoes?
Management:Disease free seed tubers should be used for planting. Because spores in the soil are the main source of infection, infected plant matter should be cleaned up and thrown away. Very early spraying with Zineb or captan 0. 2% and repeating it for every 15 – 20 days gives effective control.
What are the first signs of potato blight?
How do you treat early blight?
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- Crop rotation: Rotating crops helps break the disease cycle by preventing the build-up of fungal spores in the soil.
- Avoid overhead irrigation: Overhead irrigation can splash fungal spores onto healthy plants, so drip irrigation or soaker hoses are recommended.
- Improve air circulation: Staking plants or pruning branches can improve airflow, which helps keep leaves dry and reduces the risk of fungal growth.
- Crop rotation: Rotating crops helps break the disease cycle by preventing the build-up of fungal spores in the soil.
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- Prune and discard: Remove and discard all affected leaves and stems to prevent the disease from spreading to other plants.
- Burn or bury: Disposing of infected plant material in a way that prevents further spread, such as burning or burying, is crucial.
- Prune and discard: Remove and discard all affected leaves and stems to prevent the disease from spreading to other plants.
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Fungicide Application:
- Synthetic Fungicides: Copper-based fungicides are a common choice, but it’s essential to follow label instructions carefully.
- Organic Fungicides: Options like baking soda spray or garlic infusion can be used as alternatives to synthetic fungicides.
- Timing is key: Fungicides should be applied early in the season, before symptoms appear, or at the first sign of infection.
- Repeat applications: Regular applications may be necessary, especially during wet weather, to maintain control.
- Synthetic Fungicides: Copper-based fungicides are a common choice, but it’s essential to follow label instructions carefully.
What is the best fuNgiCiDe for potato early blight?
LATe bLIghT And eArLy bLIghT – No MatCh foR Revus toP fuNgiCiDe. When the same disease control options aren’t enough for late and early blight, potato growers rely on the superior performance of Revus Top® fungicide.