Dealing with Bitter Rot Pear Disease

What can be done to stop the problem of bitter rot pear disease?

Karen left me a message asking me if I knew how to deal with Deformed Rotting Bartlett Pears growing on  her daughter’s beautiful tree.

Here’s what she wrote:

Daughter has a bartlet pear tree that reaped abundant HUGE fruit this year which was, unfortunately, deformed with indentations and black ‘holes’  . . .don’t know what the problem is and don’t know if spraying for a ‘fungus’ is appropriate. ????  Please enlighten us. Hate to see all this beautiful fruit going to the hornets.”

Identifying the problem:

The first thing to do is to identify the problem by researching it online and in my gardening books.  The question is,” Is this pear rot problem caused by a fungus or an insect?”

Since Karen  said nothing about leaves or branches being attacked or infected, I presumed only the fruit had been affected.  I could eliminate any problems which involved more than the fruit.

When I was researching the material, I came across a comprehensive pdf  presented by the West Virginia University at, where all the diseases/problems re fruit trees were explained in detail.

Picture of bitter rot in peach is courtesy of where you can find even more info about bitter rot

bitter rot fungus disease found in pears and peachesThe only pear pest I found that involved only the fruit was called “bitter rot“.  According to the University’s information, bitter rot can be found on pears or peaches and is usually found on the fruit only.  It is caused by a fungus that can get through the unbroken skin of the fruit.

The article on bitter rot presented by the University continued to explain that “at midsummer or later, one can notice one or many  small, light-brown, circular spot(s) on the fruit.  If it’s quite hot, these spots enlarge quite quickly and soon change to a dark brown color.  As they gradually reach 1/8 to 1/4 inch in diameter, the area becomes sunken in or shaped like a saucer. When the spots reach 1/2 inch one can see small black dots in the sunken area. As the fruit ripens, it decays rapidly and finally shrivels into a mummy.”

Disease Cycle

It was interesting to find out that bitter rot is produced via fungus spores. The mummified fruit with the fungus still alive in it  ends up on the ground while fungus spores, spread by wind and/or rain, end up in cracks and crevices in the bark or in the jagged ends of broken limbs. The fungus produces more spores which eventually are washed by rain unto the fruit.  Then the cycle continues.

Ideal conditions for the bacteria to grow and multiply is humidity between 80% to 100% (lots of rain) and a temperature of  85 F or higher.”

Now that I know the problem is bitter rot caused by fungus,
I would take the following 5 steps.

Step 1. The most important action that is needed to eliminate bitter rot in  pears is to thoroughly clean up the area around her pear tree. That means cleaning up all the leaves, fallen fruit, dead wood/debris under and around the tree and send all to the garbage or burn it.

This debris should never be placed in the backyard compost bin. It is important to constantly pick up the fallen fruit to avoid fungus spores of the  bitter rot disease from being blown back onto the tree and fruit and perpetuating the problem.

Step 2. Once all the tree’s surroundings is cleaned up, I would make sure the bitter rot spores do not have a chance to survive by making the tree’s health stronger.  In order to be healthier, the tree must be properly nourished.

In order for the tree to stay healthy, it must be able to absorb nutrition from the soil. To permit absorption, the soil’s pH should be between 5.5 and 7 and should be rich loamy soil that drains well..

For further instructions on how to check the soil’s pH, you might want to go to and read the article “Testing Your Soil” found  under the category “Backyard Gardening”.

To avoid further problems with bitter rot, the soil under the pear tree should have a pH between 5.5 and 7.  The article will tell you what to do if it isn’t.

To find out how to check whether you have loam or something else as soil, read “Texture of  soils“  which is  found at

In that article, you will also find a video which will help you even more.

If the soil is clay or sand, it must be remedied.  However, no matter the type of soil you have, if you want loamy soil, simply keep adding compost which will provide the tree with nutrition.

If you don’t have compost, as a second choice one could work in some old “aged” manure in the soil around the tree base.  A third choice is to use those “fruit stakes” found in the spring at gardening stores/nurseries and pound them in the soil under the tree. . . definitely not as good as compost or manure because it does not have as wide a range of micronutrients and macronutrients as compost/manure.

(Note: if you get manure from a farmer the manure must be at least one year old manure i.e. aged manure.  Otherwise it’s safer to buy the manure at a nursery.)

I would add plenty of compost (at least 2 inches — you can never use too much compost) around the perimeter of the tree, but this compost should barely touch the trunk of the tree. (It would be great if you added wood mulch, but not the colored stuff, on top of the composted material.) The bulk of the composted material (and wood mulch if you have it) would be  spread from the trunk outward towards and under  the tree’s drip line.

Steps 1, 2, and 3 should be done as soon as possible in the early fall.

Step 4 Early in the spring before  the buds come out and after the weather stays above the freezing point , I would spray the pear tree . . . every crevice,  nook, and cranny on the trunk and branches  with horticultural oil.

For more information on how to do that, please check the article “Natural and Organic Fruit Tree Sprays” at my blog

I just found out that there is a brand new organic horticultural oil made with Himalayan Cedarwood oil.  This is just new, but I know that cedar oil is wood base oil and has been around for a long time.

This RX Horticultural Oil  is being advertised as being enhanced by the powerful insecticidal and anti-fungal properties of Cedar Oil, great for eliminating  stubborn insects and disease. The best part is that it is safe around people and pets.

So anyone living in Florida might find this product at a  local nursery.  However, you can read more about it (or buy it online) at .

Regardless, in order to  kill the stray bitter rot spores which may have overwintered in the crevices on the tree trunk, the tree must be sprayed with at least horticultural oil and maybe with what nurseries call “dormant spray,” a mixture of sulfur and oil (although I personally would try oil only because I hate working with the sulfur mixture)

Step 5 As a further precaution against bitter rot, I would continue with a spraying program after this initial spraying with the oil.  I would spray the tree  every 15 days (or more often if it rains) with the home made recipe which can be found outlined in the article “Natural Sprays for Fruit Trees” (on this blog).

I have used this recipe over and over from early spring till fall as a prevention program on all my fruit trees . . . one of them being a pear tree.  The trees love it, especially when I added the molasses (an anti-fungus ingredient).  A second ingredient which helps get rid of fungus is the garlic.  This particular recipe should boost the pear tree’s ability to fight this bitter rot problem.

This recipe can be used all summer long as often as you wish for it’s made up of ingredients found in your cupboard.  Just be sure to spray EARLY IN THE MORNING when there’s no wind and before the sun gets hot.

Having said all this, I strongly encourage Karen to get a second or even a third opinion from nursery owners who may have seen these conditions ruining the pear fruit on trees in her area.  All I’ve done here is explain how I would deal with the situation.  There are many factors which are missing; however,  although I’m pretty sure I’ve identified the correct issue when I say the pear tree is being attacked by a bitter rot fungus, it’s always wise to double check.

However, no matter the fungus or the insect causing this problem, you will have to spray to get rid of it.  Remember it’s better to prevent than to cure, especially if you can use eco-friendly products.

Karen, if you read this, I would love some feed back regarding your tree.  I hope I wasn’t too late with my response and that you will end up eliminating bitter rot on your pear tree forever.

Good luck!


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