Scab Disease

Scab Disease

Thanks to SPSnet

We've covered a lot of bugs in this blog, now let's tackle diseases.

What is it?

Scab disease is a fungal infection that harms and sometimes kills many fruit trees. Among the most susceptible are apple trees and crabapples. The main cause of this disease is a wet, cool spring. The fungus could come from surrounding trees or from a previously unknown infection on the tree the year before.

Little early to look this bare, eh?

What does it do?

The way it spreads: The fungus is intoduced to the plant by spores coming off of leaves on the ground from the previous year. The rain releases the spores which may end up on the living leaves of the tree. Once it gets on the leaves, it penetrates through to the susceptible tissue under a film of water. Then the fungus makes a different kind of spore and spreads to the rest of the tree, causing several health issues including:

• Dark areas on the leaves which can be purple, black or green and sooty or risen on the leaf itself
• Heavily damaged shoots will start dying back
• leaves turning yellow, often resulting in premature leaf-drop
• Budding hampered, sometimes the buds will turn black and hang on, even though they're dead
• "scabbing" on the fruit itself, making the fruit look rotten, cracked, or just plain inedible

Scabbing on the leaves of an Apple tree. 

This disease can make your trees look horrible. It changes the color of the leaves, makes them wilt, and often makes the leaves drop far before they are supposed to. It will ruin the fruit or make it drop before it's ripe. Not to mention, it's just unsightly to see a wilted, brown and purple, half covered tree.

How to manage it:

• The best way to deal with Scab Disease is, of course, to not have to deal with it at all. If possible, buy varieties of trees that are resistant to Scab disease. If you already have the trees, read on...
• To slow it down you can make sure that when the leaves drop, you get them cleaned up and destroyed as soon as possible. The dead leaves are what infects the new leaves the following year, so making sure they're gone will lower the risk of high infection. 
• The best approach is to hire a local tree care service to spray the trees with a fungicidal spray twice in the spring. This kills off the fungus and also may help keep other bugs from attacking the tree. These applications on average are one of the cheaper ones to get. 

Pictures thanks to: majestictreecare.com/Majestic_main/WebLinks/services.html