Early blight on tomatoes, potatoes, peppers and eggplant. Can it be subdued?

Alternaria solani is the fungus causing Early Blight. Spring brings the rain, wind, and insects traveling from plant to plant plus a hidden visitor of Alternaria solani spores. Overhead irrigation, tools, infected seed and working in the garden when wet also support spore dispersal and growth. Rain splashing from the soil, carry these spores to your plants.

Spores enter the plant through leaf surfaces or wounded plant material. The fungus spores can linger, producing many “seasons” of infection and take advantage of the hot, wet weather of late summer.

Early Blight is favored by warm temperatures and extended periods of leaf wetness from frequent rain, fog, or dew. Warm, humid  temperatures of 75-86 degrees increase the likelihood of infection.

Once the spores have “attacked”, infections have occurred and become the most important source of new spore production and rapid spread of the blight. Lesions generally appear quickly under warm, moist conditions on older foliage and are usually visible within 5-7 days after infection.

Early blight can develop quickly mid- to late season and is more severe when plants are stressed by poor nutrition, drought, other diseases, or pests.

What are the symptoms?

  • Dark spots will start showing on the older leaves of your tomatoes, potatoes, Bell pepper, hot pepper and eggplant.
  • These spots will look like concentric rings.
  • Tissue surrounding these brown spots will turn yellow (a yellow halo)
  • Spots enlarge becoming leathery, merge and leaves start to hang withered or fall off.
  • Younger leaves will start showing black spots as well as the stems.
  • As the leaves fall, the fruit has no shading and succumb to sunscald. This will also cause reduced fruiting as there is less leafing for photosynthesis.
  • Infected fruit have dark, sunken, leathery spots near the stem end. Both green and ripe fruit are affected.

tomato-early-blight1       tomato Early-blight

13_StemsTomato4       eblight3lg1_fruit

  • Tomatoes will rot from the stem to the inside of the fruit.
  • Tubers of the potato vine develop dark specks resulting in a corky potato.

What can be done to stop this blight?

  • Apply mulch (black plastic, straw, newspaper, biodegradable weed barrier)  to protect the plant from spore splashing from the soil onto lower leaves. Remember early blight is a soil borne disease.
  • Provide plenty of space between the plants. Good air flow will help keep the plants dry.
  • Pick off affected/infected leaves and remove them from the garden, bagged; dispose with household garbage. Burning is equally effective.
  • Wash your hands and/or gloves when you finish in the blighted area.
  • Change your clothes to reduce further spore dispersal.
  • Wash/disinfect any tools used in the blighted area.
  •  Use a biofungicide spray: Bacillus subtilis,  (Serenade® MAX) and Bacillus pumilis (Sonata®) with compost tea. Read label for application.
  •  Copper products, hydrogen peroxide, and potassium bicarbonate can be used against early blight . Read the label for application.
  • Garlic, neem oil and seaweed extract have also been shown to be effective in reducing the severity of early blight disease on tomatoes. Spray and apply as label directs.
  • Do not work in the garden when it is wet after rain, morning dew or fog.
  • Use drip irrigation as this will keep the plants dry.
  • Rotate your tomatoes, potatoes, Bell and hot peppers and eggplant every three to four years with small grains (wheat, barley, rye, oats, sorghum), corn and legumes (peanuts, peas, cowpeas, green beans, long beans, runner beans, fava beans, soybeans, Southern peas, sugar snap peas). If you are limited on space consider container and vertical gardening giving your soil time to regain its health and decrease the spore population.
  • Amend your soil with compost during late fall as it supports microorganisms that contribute to biological control in the soil.
  • Early blight survives from season to season in or on the leaves, stalk and fruit from diseased plants.  Remove diseased plants or destroy them immediately after harvest.(Bag or burn)
  • Nightshade and horsenettle  serve as alternative hosts for the disease. Remove them from your garden area.
  • blacknightshade_orig       Horse-nettle-plant1
  • Tomato stakes and cages should be disinfected (hydrogen peroxide or diluted bleach solution) and rinsed prior to storage. All dried plant material must be removed, bagged or burned.
  • Be alert to weather changes.
  • Become a plant detective. Get out to the garden daily and observe for any changes. You won’t be sorry as you are on the watch for disease. Removing leaves at the first sign of infection will slow the spread of Early Blight.
  • Do not compost any diseased plant material.
  • Do not save seed from diseased fruit as Early Blight survives within them.

Are there Early Blight “resistant” tomato varieties? More like partially resistant.

  • Mountain Pride
  • Mountain Supreme
  • Mountain Gold
  • Mountain Fresh
  • Mountain Belle
  • Mountain Fresh Plus
  • Aunt Jenny’s Purple
  • Big Rainbow
  • Black Plum
  • Juliet
  • Legend
  • Matt’s Wild Cherry
  • Old Brooks
  • Tigerella (AKA Mr. Stripey)
  • Tommy Toes

What is a good strategy for potatoes?

  • Choose resistant varieties such as long season as they are usually more resistant – Certified seed potatoes.
  • Choose a short season variety, plant early and harvest before Early Blight invades.
  • Separate your potatoes from your tomatoes to decrease cross infection.
  • Give wider spacing to access better drying and air flow.
  • Be aware of the moisture in the soil. Do not over water.

Yes, Early Blight can be subdued if you are vigilant.

Papa

Advertisements

There are White Spots on my Peas! Uh Oh, it’s Powdery Mildew!

The daytime temperatures are getting warm and it’s cool at night. It seems like the perfect scenario for great growing weather. Your peas are up and growing like a storm. What’s that on the leaves and pods? There are white fuzzy spots growing on my peas. Powdery Mildew strikes again!!

peapm

Powdery mildew is the most common occurring plant fungal disease. Its appearance, when first noticed, is characterized by spots or patches of white to grayish powdery growth on the upper surface of leaves and their stems.

  • It impairs photosynthesis
  • Stunts growth
  • Increases the rate of plant decline

Advanced stage of powdery mildew:

  • Foliage turns to yellow, leaves curl or turn brown.
    • D-TO-LTAU-FO.001h        D-SP-EPOL-FR.001h

How does this happen? There are three requirements for disease to flourish. A host, the pathogen/disease and the right environmental conditions.

  • Powdery mildew (thin layers of fungal tissue on the surface of the leaf which produce spores) requires new and young living plant tissue to grow.
    • The disease grows as mycelium (fungal tissue) on the surface of the affected plant as white patches where the spores are produced.
      • Spores make up the white/gray powdery growth visible on the leaf surface.
      • Spores  of powdery mildew are carried by the wind, splashing rain drops and/or insects to new plant tissue.
      • The spores can produce in 48 hours.
  • Warm, humid days and cool nights are the perfect conditions for the fungus to grow.
    • Moderate temperatures of 60° to 80° (F) are favorable temperatures for powdery mildew growth.
    • Temperatures of 90° (F) and above inhibits the growth of the disease.
  • High humidity for spore germination common in crowded plantings, where air circulation is poor and damp shaded areas invite this plant fungal disease.
  • Crop debris and host weeds are important to the survival of powdery mildew.
  • The spores of powdery mildew over winter attached to plant parts and plant debris.

These are the common preemptive strategies to avoid/combat powdery mildew.

  • Plant powdery mildew resistant varieties if available.
  • Plant in full sun.
  • Properly space plantings to allow good air circulation.
    • If plants are overcrowded, prune to allow increased air circulation, reduce humidity and cross infection.
  • Arrange your rows or beds east to west to eliminate shade possibility.
  • Tallest plantings should be to the north.
  • Avoid overhead watering. Best time to water is mid morning allowing the plants to completely dry.
  • Stay out of the garden when wet!!! Otherwise, you become a carrier of the disease.
  • Avoid the late summer application of nitrogen fertilizer (fish emulsion, composted poultry litter, ammonia nitrate, urea) which limits new growth the disease attacks.
  • Remove ALL diseased plant parts and burn or bag and remove from property.
    • If possible, remove diseased plant parts on a sunny, hot, wind free day.
      • Spores are killed by heat and direct sunlight.
      • In the absence of wind there is less of a chance for spore dispersal.
  • Remove ALL plant material and plant debris (mulch included) in the fall.
    • Survival rate of any overwintering fungal spores is decreased.
  • DO NOT COMPOST ANY PLANT MATERIAL OR DEBRIS where this disease was active.

When fungus pressure/threshold is too great you can pull all diseased plants or are there fungicides to use? The answer is YES!!

  • Horticultural oils – Saf-T-Side Spray Oil®, Sunspray Ultra Fine Spray Oil® – follow label directions
  • Neem Oil (plant based), Jojoba Oil (plant based) – follow label directions
    • Never apply when temperatures are 90° (F) or above or with drought stressed plants.
    • Never apply an oil spray within two (2) weeks of a sulfur application as plants may be damaged.
  • Wettable Sulfur is most effective when applied before disease symptoms appear. – Safer Garden Fungicide® – follow label directions
    • Never apply when temperatures are 90° (F) or above or with drought stressed plants.
    • Never apply within two (2) weeks of an oil spray.
    • Be careful when spraying squash and melons as there may be damage.
  • Baking soda ( Sodium Bicarbonate)
    • Combine with horticultural/dormant oil with liquid/insecticidal soap
      • 1 TBS Baking Soda, 1 tsp horticultural/dormant oil, 1 tsp insecticidal/liquid soap to 1 gallon of water.
      • Spray every one to two weeks.
      • Use sparingly to avoid sweetening (alkaline) the soil.
  • Potassium Bicarbonate – Kaligreen® – contact fungicide killing spores of powdery mildew quickly.
    • Approved for organic use. Follow label directions.
  • Mouthwash – generic ethanol based – spray 1 part mouthwash to 3 parts water.
    • Caution use on new foliage as it may be damaged.
  • Vinegar – spray 2 -3 TBS apple cider vinegar (5% acetic acid) mixed with 1 gallon water.
    • Caution use on new foliage as it may be damaged.
  • Milk – natural occurring compounds in milk attack the disease while improving the plants immune system.
    • Spray 1 part milk to 2 parts water weekly.

Biological Fungicides – beneficial microorganisms when sprayed on plant tissue destroy fungal disease. Serenade®, Actinovate AG®, Cease®

  • Active ingredient  – Bacillus subtillis – prevents powdery mildew from infecting the plant. Follow label directions.
    • Non toxic to people, pets and beneficial insects
      • Not proven to be as effective as oils or sulfur

Here are a few examples of powdery mildew.

powdery_mildew_tomatoes      carrot-powdery-mildew-1L

9-4PM-on-grape-leaves-1ANNEMIEK (1)       PMSquashBHedlundHerndonVA2006-1y47tkc

PM watermelon

Remember, fall clean-up is essential!! Be on your guard!

Papa