Written collaboratively by Ruth Beck and Febina Mathew.
Producers of field peas may need to scout for powdery mildew this year. Powdery mildew is a late-season fungal disease that can impact peas if weather conditions are conducive. Peas that are planted late are usually more susceptible to powdery mildew than those planted early. However, this disease can also occur in early planted fields in South Dakota under the right environmental conditions and when the crop canopy is heavy.
Symptoms of powdery mildew begin with white powdery spots that occur first on the upper surface of the oldest leaves and stipules and then on stems and pods. Warm dry weather accompanied by cool nights with dews is conducive to the spread of this disease. Many varieties are resistant to this disease. Producers should select and grow resistant varieties if possible to avoid any chance of this disease. However, this is not always an option for producers.
Management
If producers are growing varieties which are susceptible to powdery mildew and weather is conducive to disease development they should scout the canopy every 2 days beginning at early pod development. If conditions are high risk for disease development scouting should start when the first pods are at full length, otherwise scouting can start when the first pods are filled. Fungicide applications should be made when the first symptoms of powdery mildew are detected at low levels in the lower canopy.
Producers may want to consider a preventative fungicide treatment if they are not able to monitor the fields as needed. However this is only necessary if the weather is conducive to disease development and varieties do not have resistance. Powdery mildew does not occur every year in South Dakota. Fungicide timing is important. Most fungicides provide protection for up to two weeks. The goal is to apply the fungicide before disease exceeds low levels but not too far in advance of initial disease onset, as you want high levels of fungicide residual remaining in the plant when disease begins to develop. Preventative fungicides such as Proline, Quadris, Headline, and Priaxor can be applied during bloom to late pod fill. These fungicides have shown efficacy in field trials conducted in previous years.
Figure 2. White film on pea leaf.
It is important that this disease is properly identified. Powdery mildew can affect the entire field when varieties are susceptible. Peas naturally can have a white film on their leaves during growth and this can be mistaken for powdery mildew.
A good resource for labelled fungicide options on field peas is the NDSU Field Crop Disease Management Guide. For more information on field pea disease concerns, view the publication, “An Identification Guide of Common Diseases of Dry Peas in South Dakota.”
Powdery mildew is a common disease that afflicts many plants, and peas are no exception. Powdery mildew of peas can cause a variety of problems, including stunted or distorted growth, decreased harvest, and small, flavorless peas.
Since powdery mildew primarily affects plant foliage, fruit and vegetables from afflicted plants are still safe to eat, but refrain from consuming any leaves.
Crop rotation with non-related crops will help. Field isolation may assist in reducing infection which occurs by wind movement. Avoid heavy application of fertilizer. Foliar fungicides should only be necessary when the disease appears early in the growing season or if the crop was planted late.
Expert Response. Soaking leaves in hydrogen peroxide will kill powdery mildew. However, I would not recommend eating leaves with powdery mildew on them. Powdery mildew is not toxic to humans, but fungi cause allergic reactions in some people.
Quick facts. Powdery mildew is a common fungal disease that affects many different plants in the flower garden. May cause plants to look less attractive but doesn't cause significant damage. When severe, the disease may reduce plant growth and flowering.
If powdery mildew is mild to moderate, try spraying pea plants with a plant based horticultural oil such as neem oil. Never spray when the temperature is above 90 degrees F. (32 C.). You can also spray peas with commercial fungicide at the first sign of the disease.
Although white powdery mildew does not pose a direct threat to humans, it can be indirectly harmful. It won't hurt you if you touch it, but if you are allergic to mold and you pick or consume a plant infected with mildew, you can have a serious reaction to it.
Powdery mildew can be treated early on with fungicides including potassium bicarbonate, neem oil, sulfur, or copper. Home remedies like baking soda and milk can also be successful treatments when applied properly.
Powdery mildew fungicide: Use sulfur-containing organic fungicides as both preventive and treatment for existing infections. Trim or prune: Remove the affected leaves, stems, buds, fruit or vegetables from the plant and discard. Some perennials can be cut down to the ground and new growth will emerge.
The soap acts as a desiccant on contact with powdery mildew. The application of soap sprays is more effective if used as a preventative measure than when used to eradicate powdery mildew after infestation has occurred.
If powdery mildew has taken over your plants, it's best to first remove any infected portions, immediately throwing them away rather than composting them. This will help prevent spores from spreading to other plants or future outbreaks from occurring.
If you do see mildew in spite of your watering care, spray infected plants at the first sign of white spots. Mildew will not go away without spraying, and the longer you delay, the harder it is to control.
Is Powdery Mildew Harmful to Humans. Whilst this fungus has no direct negative effects on humans (including human contact), it can cause problems for many people who are allergic to this particular mould or suffer breathing problems.
If I wash the pea pods before eating them are they safe to eat? Powdery mildew is not toxic or poisonous to humans, but an allergic reaction can occur. Check the inside of the pod for any signs of mold developing. If the inside and outside of the pod is free of mold it should be good to eat.
Powdery mildew is a late-season fungal disease that can impact peas if weather conditions are conducive. Peas that are planted late are usually more susceptible to powdery mildew than those planted early.
Powdery mildew in field peas is caused by the fungus Erysiphe polygoni. Infected plants are covered with a white powdery spore mass (see Figures 1 and 5). Leaves, stems and pods can become infected, resulting in withering of the whole plant. Spore masses are present on both sides of the leaf.
Oils alone can be used to control powdery mildew. Vegetable seed oils such as canola oil can be used, at a rate of 2.5 to 3 Tablespoons per gallon of water, with the addition of a quarter-teaspoon of liquid soap to emulsify the oil.
Introduction: My name is Chrissy Homenick, I am a tender, funny, determined, tender, glorious, fancy, enthusiastic person who loves writing and wants to share my knowledge and understanding with you.
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