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Fungal Disease Protocol

Oh, summer... the season of heat, humidity, hustle, and harvests! With the heat and humidity, and sometimes a pop-up afternoon rain shower, come a few challenges for maintaining plant health and vitality.

Fungal disease goes hand-in-hand with growing summertime favorites. Tomato, cucumber, and squash plants are particularly susceptible to fungal disease. With their broad, low-lying leaves in addition to the heat and humidity, there is an easy bridge for fungal spores to jump from the moist soil to our summer crops. Therefore, we usually notice fungal disease like early, late blight, or septoria spot on tomatoes and powdery or downy mildew on cucumbers and squash first on the lowest leaves of the plant.

These fungal diseases manifest in different ways but usually some kind of discoloration of the leaves in splotchy or ringed patterns. If you are growing these plants, and you notice discoloration of leaves on the lower half of the plant, it's safe to assume you have a fungal disease to treat. Here's a quick diagnostic for these top summer fungal diseases -

Early blight on tomato leaf

Common Tomato Fungal Disease

  • Early Blight: yellowing of leaves, formation of round "ringed" (like a bullseye) brown spots on the edges of leaves

  • Late Blight: dark grey-ish brown splotches on leaves

  • Septoria Spot: small, dark brown spots on leaves with yellow rings around each spot

Common Cucumber / Squash Fungal Disease

  • Powdery Mildew: bright white, soft-edged splotches on the tops of leaves

  • Downy Mildew: yellow, brown, and grey-ish blue splotches on leaves, starting on the bottom of leaves and bleeding into the tops of leaves

Powdery mildew on zucchini leaf

It is important to remember anytime we are growing plants, we are cultivating an ecosystem. A plant ecosystem also includes bacteria, fungi, and animals of all sizes and shapes. My goal is always to strive for a happy co-existence within this ecosystem.

If you suspect you have a fungal disease, it is important to know that fungus spreads through spores, in moist conditions, and through contact. Don't touch your leaves unless you're ready to conduct a full treatment of the plant, which involves removing affected leaves and treating with a fungicide you feel comfortable with. I love a diluted neem oil concentrate.

For more on cucumber and squash fungus, and how to treat your plants with fungal diseases, consider purchasing this digital download.

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