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Determine leaf diseases: damage patterns on diseased leaves

22.08.2022  /  Reading time: 9 minutes

During the regular inspection tour of your garden, you discover that some plants are diseased. There are changes on the leaves that indicate a plant disease. But which leaf disease could it be? Here is an overview of the most common leaf diseases and their symptoms.

This article contains:

  1. Mosaic virus
  2. Botrytis bunch rot (Botrytis cinerea)
  3. Leaf curl (Taphrina deformans)
  4. Late blight (Phytophthora infestans)
  5. Mildew
  6. Rust fungi (Pucciniales)
  7. Scab (Fusicladium)
  8. Sooty mold (Diplocarpon rosae)
  9. PDF: common leaf diseases in the garden
  10. Frequently asked questions about leaf diseases

Quick Overview

Common leaf diseases in the garden and their symptoms

  • Yellow mosaic virus: mosaic-like, yellow-green brightening on the leaves
  • Gray rot: dense grayish-white fungal coating
  • Curling disease: curled leaves with light green or red blisters on the upper side
  • Late blight: olive-brown spots on the upper side and white fungal turf on the underside
  • Powdery/false mildew: wipeable white fungal coating on the upper side of the leaf/purple-white coating on the underside; yellow-brown spots on the upper side
  • Rust fungi: rust-brown spots on the upper side; pustules on the underside with fungal spores
  • Scab: gray-black spots on the upper side of the leaf
  • Star sooty mold: black-brown spots that spread in a star shape

Mosaic virus

  • Symptoms: mosaic-like, yellow-light green pattern on the leaves; wilting; leaves curl, turn yellow and die; later also deformation of fruits and shoots; often transmitted by pests such as aphids, whiteflies and thrips (like most viral diseases)
  • Susceptible plants: especially nightshade plants such as tomatoes and potatoes; cucurbits such as cucumbers, melons and zucchinis; fruit trees and vines
  • Combating and preventing mosaic virus (unfortunately the article is still missing, but will be added soon!)
Cucumber mosaic virus
This is what the damage caused by the cucumber mosaic virus looks like. This virus is often transmitted by pests. Image by DieterO on Wikimedia Commons.

Botrytis bunch rot (Botrytis cinerea)

  • Symptoms: grayish-white fungal coating on the leaves and later also on other parts of the plant; later, infected parts begin to rot and die off
  • Infestation with gray mold (Botrytis cinerea) is particularly relevant for the hobby garden because gray mold can infest over 200 host plants!
  • susceptible plants: Viticulture (noble rot!); lettuce, cucumbers, beans, tomatoes, onions, roses, strawberries, blackberries, raspberries, gooseberries
  • Combat and prevent gray mold (unfortunately the article is still missing, but will be added soon!)
Botrytis-infested tomato
Gray mold spreads throughout the plant and causes major crop losses. Image by Rasbak (CC BY-SA 3.0) on Wikimedia Commons.

Leaf curl (Taphrina deformans)

  • Symptoms: young leaves curl and become lighter in color; light green or red blisters on the upper side of the leaves; early leaf fall
  • Susceptible plants: mainly fruit trees such as peaches, nectarines and almonds
  • Combating and preventing curl disease (unfortunately the article is still missing, but will be added soon!)
Curl disease
If the young leaves on your fruit tree are curling, you are probably dealing with curl disease. Image by Schwäbian on Wikimedia Commons (CC BY-SA 3.0)

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Late blight (Phytophthora infestans)

  • Symptoms: olive-brown spots on the upper leaf surface; white fungal turf on the lower leaf surface; leaves curl up; later browning of the stems and fruits; over time, leaves turn black and wilt; plant reacts with early leaf fall
  • Susceptible plants: mainly nightshade plants, such as tomatoes, potatoes, eggplants and peppers
  • In the event of an infestation, you can find tips on how to combat and prevent late blight here
Brown rot on tomato leaves.
Blight is a very common plant disease in tomatoes! Image by Scot Nelson on Wikimedia Commons (CC 1.0 universal public domain dedication)

Mildew

Powdery mildew (Erysiphaceae)

  • Symptoms: infects the upper side of leaves with a whitish, floury coating that can be wiped off (fair-weather fungus)
  • Susceptible plants: Woody plants such as apples, grapevines, gooseberries, roses; vegetables such as zucchinis, cucumbers, pumpkins, melons, carrots, peas, salsify, sage, strawberries
  • You can findtips on how to combat and prevent powdery mildew in the article on the topic
Powdery mildew on zucchini leaves.
Powdery mildew is a fair-weather fungus!

Downy mildew (Perenospora)

  • Symptoms: manifested mainly by a purplish-whitish coating on the underside of the leaves (cannot be wiped off!); yellow-brown spots on the upper side of the plant's leaves
  • Susceptible plants: Vegetables such as radishes, radishes, horseradish, lettuce, peas, lamb's lettuce, cabbage, spinach, onions; woody plants such as roses and vines (grapes)
  • Fighting and preventing downy mildew
Downy mildew on zucchinis
Downy mildew is similar to the yellow mosaic virus. So take a close look to see if you can find a fungal coating or insects on the underside of the leaf. Image by Christian Hummert on Wikimedia Commons (CC BY-SA 3.0)

Rust fungi (Pucciniales)

  • Symptoms: small brown-red rust spots on the upper side of the leaf; rust-red pustules with fungal spores spread to the underside of the leaf (with the exception of white rust, where the pustules are white); infected parts of the plant die; some shoots are also infected
  • susceptible plants: Apples (apple rust), pears (pear rust), currants (currant column rust), cereals (cereal black rust, yellow rust), asparagus, carrots, onions, peas, beans and turnips
  • Combating and preventing rust fungi (unfortunately the article is still missing, but will be added soon!)
Pear lattice grate
Does your pear tree look like this? Then it is probably infested with pear rust.

Scab (Fusicladium)

  • Symptoms: gray-black spots on the blossoms and brown-black spots on the upper side of the leaves and later also on the fruit; early leaf drop
  • The most common scab disease is apple scab(Venturia inaequalis). Scab is caused by a fungus.
  • Susceptible plants: especially plants from the rose family (apples, pears, roses, etc.), potatoes (potato scab)
  • Fighting and preventing scab (unfortunately the article is still missing, but will be added soon!)
Potato with potato scab
This is what potato scab looks like. In addition to the leaves, the tubers are also affected. Image by Rasbak on Wikimedia Commens (CC BY-SA 3.0).

Sooty mold (Diplocarpon rosae)

  • also called black spot disease
  • This disease is caused by a fungus
  • Symptoms: round black-brown spots on the leaves, which often spread in a star shape and end in jagged edges; leaves turn yellow and fall off
  • Susceptible plants: mainly plants of the Rosaceae family (roses, pears, apples), rarely cucumbers
  • Combat and prevent star sooty mold (unfortunately the article is still missing, but will be added soon!)
Star sooty mold is a common plant disease of roses. Rasbak on Wikimedia Commons.

Hopefully you have found out which leaf disease you are dealing with! We'll keep our fingers crossed that your plants get well again!

As some diseases and pests are difficult to control using biological means, you should definitely take preventative measures to protect your plants in the garden. You can find tips on biological plant protection in the article on the topic!


To prevent leaf diseases and diseases in general, it is important to obtain high-quality seeds! In our Fryd store you will find a diverse selection of seed leaders, robust varieties. Take a look and let yourself be inspired.

If you have any questions or comments about gardening, please write to us at [email protected]. You will also find many like-minded people in the community in our app. Here you can also ask questions and get tips from experienced gardeners on how to deal with diseases.

Do you want to get helpful gardening tips all year round and plan your own beds optimally? Then register here or download the Fryd app for Android or iOS.

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Author

Marie

Marie studied agricultural science at the University of Hohenheim. Her main focus is on ecological agriculture and permaculture. She writes articles for Fryd to educate people about ecological interrelationships and alternatives to current land use. Our current economic systems, especially in agriculture, have numerous negative effects on nature and destabilize our ecosystems. We need a great diversity in our gardens and beds again to counteract the extinction of species. Every gardener can contribute to creating and maintaining habitats and food for a wide variety of creatures. With her articles, she would like to pass on her experience in dealing with natural systems and give people the opportunity to contribute to a stable ecosystem and thus also to securing our livelihood.

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FAQ

Powdery mildew shows a wipeable, whitish-mealy coating on the upper side of the leaf, while downy mildew has a purplish-whitish coating on the underside of the leaf.

Botrytis is characterized by a greyish-white fungal coating on the leaves, which later spreads to other parts of the plant. The plant dies.

Round, black-brown spots on the leaves, which often spread in a star shape and end in jagged edges; leads to yellowing and dropping of the leaves.

A dense, grayish-white fungal coating on leaves and other parts of the plant, which later leads to rotting and death of the affected parts.

PDF: common leaf diseases in the garden

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