Fire Blight

Fire Blight

Signs of Fire Blight on a Pear tree.

What is it?

Fire Blight is a disease that usually attacks Apples and Pears. It's caused by a bacteria that survives the winters in branch and trunk cankers(1). Once springtime rolls around, the bacteria begins multiplying once the temperature is above 65 degrees.

Infected trunk of an Apple tree

Do you have it?

You can sometimes see the white, liquid bacteria oozing out of cankers on the tree. It is called Fire Blight because of the symptoms it causes. It will look like the leaves, flowers, and small twigs have been scorched away. You'll usually notice the symptoms rather early in the year.

What does it do?

The infection starts in tip shoot tips and moves downward all the way to the trunk. The leaves will start turning brown or black, depending on the type of tree it is. (apples and crab apples usually turn brown, pear trees look black.) The disease will also infect fruit. This next picture is an apple infected with fire blight.

That's bacteria seeping out of it... gross.

The areas most commonly affected are the open flowers in the spring. It sometimes stays local to a certain part of the tree, but sometimes will spread to other areas. It can kill susceptible trees and even if it doesn't kill it, it can severely disfigure it. Once the tree has fire blight, it stays forever.

How to manage it:

Fire Blight can be avoided by planting certain types of trees that aren't affected by it. For example, if you want to plant a pear tree, you would want to avoid Asian and Red pears as they are the most susceptible.

If you've already got the trees then there are some tips to preventing the infection from spreading.

• Do not use excess nitrogen fertilization
• Do not prune if you can help it
• The tree should not be irrigated during the bloom cycle
• If you see an area that is showing symptoms of blight, remove and destroy it immediately
• With no cure known yet, the recommended spray to help would be a Copper blossom spray. It stops new infections, but it's detrimental that you cut the old infections out as best as you can.
• These sprays should be applied the entire time the tree is in the blossom stage, and should be applied when the temperature is above 60 degrees. Do this every 4 to 5 days until the bloom is over. This could mean as many as 12 treatments in one year.
• When trimming out infected areas, make SURE you clean your clippers after every snip. A bucket with 10% bleach in it will be fine.
• The best times to trim is in the summer and winter. During these seasons the infection has stopped reproducing and is dormant, thus making it easier to find the infection and destroy it.

(1) A canker on a tree is a small or large portion of dead bark that was killed during the previous years' infection.

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