Saturday, January 7, 2012

Let the Battle Begin: Controlling Botrytis on Quince (Cydonia oblonga)

The early signs of Botrytis cinerea on Cydonia oblonga 'Van Damen'

It may still be winter but there are things we need to be doing to prepare for a healthy harvest in the coming season.  I am looking out my front window at my Quince tree which has taken "forever" to lose its leaves this year.  It's January and there are still leave on it!  I was seriously thinking of borrowing my husband's power washer to knock them off!

"Honey, may I borrow your power washer?"

Normally it is one of the last species of trees in the neighborhood to lose its leaves.  This year however, it has been "painfully" slow due to the odd fall and winter weather and those leaves, they play a part in the increasing infection of a fungal disease that has become a growing concern this past year.

For several years we have enjoyed the beautiful fruit this little tree has given us but have always lost a small portion to rot that occurs starting at the blossom end of the fruit and if not cut away in time, will ruin the whole thing.  I have watched and wondered over the years what it was that was causing the problem but never felt the pain of the loss like I did this year when my long anticipated harvest seemed more profoundly affected than ever before.

They don't look like much but just you wait.

After watching the fruit form from it's humble homely fuzzy beginnings to glorious yellow fruit I almost couldn't wait to pick and have so many of them bear ugly brown rotting spots at the bottom I just couldn’t take it anymore...especially when I began to cut into some that looked like they only had a little brown at the base and had to toss half the fruit away!  IT WAS TIME TO TAKE ACTION!

NOOOO!  Not my beautiful fruit!!!

Laptop in hand I slapped on my investigator's hat and got online to find out what the culprit was.  (If you have not discovered this yet…online searches are an amazing and easy way to do research.)  I went to Google, typed in  “Diseased quince fruit images” and POOF!  A whole catalog of images to look at, one of which yielded information on what was wrong with my tree.

One of the things I learned when I worked as an OSU Master Gardener was to distinguish the signs of disease and insect damage carefully.  So I noted that when I cut into the Quince, there were no signs of insect damage as there might be in the case of Apple maggots...a thing I am so very grateful for too as they are a big problem here.  With this knowledge I was on to look at possible diseases.  I took note that the rotting started at the base of the fruit where the remains of the flower can be seen. It also appeared to have a hard core-lick beginning on some fruits...but the same effect which was to eventually move up and rot the whole fruit.  This would be an important clue to identifying the culprit. 

As I looked over the images in front of me I found a few that looked very much like what I was seeing.  I needed one that was from an informational site and not just a random photo.  It only took a few seconds and I had my answer.   Yes it really is that easy...well most of the time it is anyway.

My enemy as it turns out  was Botrytis..."Botrytis cinerea" to be exact, the same fungus that attacks grapes and many other plants. Botrytis, also known as Gray Mold is sometimes referred to as blossom end rot in pome fruit (apples, pears and quince) because it causes the fruit to literally rot from the bottom up.  As fungal disease in general has many forms and one that I am sure most of you have seen at one time or another.  You know that gray mold found on herbaceous plants like annual bedding plants and perennials...that is Botrytis.  It can be found in all its ugly gray moldy glory on mushy Marigold flowers or on the rotting bases of Petunias that have been kept too moist or in overcrowded flats of plants of well watered plants at garden centers.  It is one of the most unpleasant memories I have from my days working in garden centers...from Alyssum to Zinnias...give the right conditions they all seem to get it and I would rather clip slugs in half with my pruning scissors than have to clean off mushy slimy moldy plant material!  (Shudder)  But back to how to fight it.

When going to war there is a piece of wisdom that we as gardeners certainly need to remember to apply when dealing with diseases and pest..."Know your enemy!".  If you want to fight an enemy effectively you first need to understand how the enemy operates and how to take them down.   Understanding what the disease attacks, how disease spreads and the conditions it needs to grow in are all important in being able to combat it effectively. 

My enemy here, Botrytis, attaches itself to the soft fleshy tissue of new buds and emerging flowers in this case and overwinters on old leaves and on the tree itself.   This means that if the spores are present as the new buds swell and the flowers open will become infected.  I need to reduce the presence of those spores and their ability to attack the new spring growth.

All fungal diseases have three environmental elements that help them thrive; air movement, temperature and moisture levels.  If you can effectively change just one of those conditions you can slow down and prevent the fungus from spreading or even eliminate it.  So you can see why understanding is key to this battle.  However with a tree in a garden it is a little harder to change one or more of these environmental elements than say, in greenhouse where one can adjust the temperature, moisture levels and air flow more readily.  That does not leave us without options however.

I have often referred to the Pacific Northwest and Portland in particular as the “fungal jungle” since we battle fungal disease here all the time.  We learn quickly here that just clearing up old dead plant material often isn't enough.  We sometimes need to apply dormant sprays to fruit trees as a preventative measure.  This is crucial in combating these diseases as our spring weather provides near perfect conditions for Botrytis to occure.  The temperatures are warming and the spring rains leave the moisture high which produces fast lush growth in the garden...a perfect environment for Botrytis.  And I suppose I am like a lot of gardeners...I put up with some damage but the loss of a desired harvest kicked me in the fanny and got me heading in the right direction.  Thankfully, it is not too late and I have things I can still do to fight this disease and reduce future damage.

Tater...You're gonna have to move, I need to rake.

STEP ONE:  Clear away and destroy diseased leaves and any fruit from the tree.  I may as well do that for my other plants too while I am at it.  This will dramatically reduce the opportunity of future infection by removing the source of over wintering spores on spent plant material.  I will not be composting any of the leaves or fruit this year but am burning it all.

Dormant sprays need to be applied before buds begin to swell and flowers and leaves appear.

STEP TWO: Applying the recommended dormant spray. Dormant sprays are used to kill over-wintering spores that are on the branches and dormant buds of the tree.  Honestly I have never done this before as we’ve never minded some loss and fortunately our tree is small enough we can apply it ourselves easily.  Using the proper product at the proper time is crucial to stopping the spread of this disease so I checked with my local county extension office online and got the information I needed.

STEP THREE:  Maintain good cultural control measures noted in step one to reduce future outbreaks!!!

Finally I just want to say again how amazingly how easy it is to find good information online just typing in a question or the type of images needed as I did above.  It has become my habit to do an online search first and if I still need help, I contact the local county extension office or the small orchard society.  A good local garden center can be helpful too, but still, I find the internet my most helpful resource.  Oh and speaking of the internet I should make mention that social media venues are a part of those resources as well from Facebook groups to online forums.  We gardeners seem always ready and dedicated to helping others garden successfully.  So don't you ever be shy about asking a question if you need help in your garden, we are ready and willing to help.  Remember, the only stupid question one never asked.

Here's to a healthy harvest this coming season!

Happy Gardening!

NOTE: To avoid possible damage to your trees and garden, it is important to follow USDA guidelines for spray schedules for your area.  This goes for both organic and inorganic chemicals.  This will also save you time and money as well.

Copyright © 2012 by Patty Hicks

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