Symptoms Of Apple Scab Disease
Apple Scab Disease is a plant disease commonly found in domestic apples and ornamental crabapple trees. Symptoms include dark brown or black lesions on the surface of leaves and fruit. Apple scab is caused by the ascomycete fungus, Venturia inaequalis. An aggressive infection of this type will eventually reduce fruit quality, rendering it inedible. Fruit quantity is also affected. Apple Scab may occur over successive growing seasons; however, this fungus rarely kills its host. So if you are interested in planting apple trees or have a home orchard, then watch the video explaining the Apple Scab life cycle.
Video Explaining Apple Scab Life Cycle
Watch this easy to understand video explaining the critical stages that occurs during this fungal infection.
It all about moisture and temperature when it comes to apple scab infections. The wetter and warmer the weather is during springtime, the more vigorous the disease will become.
When the ascospores from Venturia inaequalis land on wet apple buds, leaves, or fruit, they germinate and grow into the apple tissue. The time required depends on temperature and the presence of a wet surface. At 39°F and 28 hours of continuous moisture will result in an infection, while between 61 to 75°F, only 6 hours are required.
After the fungus has penetrated, it continues to grow and enlarge within the plant tissues. It takes approximately 9 to 17 days for a visible scab to form. Development occurs more rapidly at higher temperatures. This initial infection is known as the primary phase.
If left untreated, a secondary infection will eventually develop on the plant surfaces, which appear as asexual conidia. These new conidiospores are easily dislodged when the lesions are wet and transferred by the wind to new leaf and fruit surfaces on the tree. This is known as the secondary phase.
Choosing Disease Resistant Varieties
Many attractive and tasty apple varieties are available that have resistance to apple scab disease. Some varieties have more resistance than others. However, these apples are still susceptible to other fungal diseases like powdery mildew and cedar apple rust. That said, gardeners may still have to use fungicides on these trees.
|Apple Cultivars: Scab Resistance Selections|
|Crimson Crisp||Gold Rush||Querina|
|Crimson Gold||Novamac **||Redfree|
|Freedom **||Enterprise **||Williams Pride **|
|** suitable for home orchards|
Purdue University explains chemical management using conventional fungicides
Some easy tips on how to get rid of Apple Scab Disease