Pear disease and Insect identification

It’s that time of the year when people start seeing a lot of diseases and insect problems with pears. I thought I would post links on how to identify pear diseases so you can better treat them. I realize there are many other general disease threads out there but I wanted to focus on pears specifically.

Pear scab
Pear Fireblight
Pear Blossom Blast

Pear rust
Pear psylla
Pear leaf blister mites
Codling moth
Plum curculio
Pear Black rot
Pear Sphaeropsis Rot
Pear Anthracnose and perennial canker

Pear decline
Pear powdery mildew

Many people are looking for an organic approach and may benefit from this guide
Need to know about the latest pear diseases? List of pear diseases - Wikipedia or or
Insect and Disease Identification Thread - #78 by speedster1 or
Stone fruits have their own diseases so if you are looking for those try this link . Trying to identify another disease ?


Thanks for posting all these links

wrt Fireblight, the UC site has the better information, except they say the only treatment available to the homeowner is copper

I wonder if this is just a CA restriction - I just ordered Fertilome’s streptomycin online

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Hope the links help someone. I agree spraying Fertilome’s streptomycin when pears are in bloom is a great idea for prevention of fireblight . Post bloom spraying as your aware won’t help. Saw some blossom blast this year so I will likely use Fertilome streptomycin next year since it is bacteria as well. Copper seems very effective against fireblight when the trees are sprayed dormant in the late fall and early spring.

The UC site was quite helpful

I’m new to FB [as I assume it is] and was wondering how long to watch for new symptoms in the shoots - the site answered that

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Clark thanks for posting those links, nice to have all in one place. Here is an additional one that I have had problems with, Fabraea Leaf spot:

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Very helpful information, thank you for posting it

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Now that fall is arriving house keeping is an important factor because many diseases are airborne from leaves, winter over in lesions in the bark. Destroy infected leaves and wood when possible. Dispose of fruit drops to control insect etc. . I paint trunks, apply rabbit guards, etc. . Take note of bacterial, fungus, or virus diseases you saw this year. Don’t forget about mites and pear psylla On the ars grin website remember some pear woods show virus infected so it’s important to be aware viruses are transmitted via grafting. Before you order or exchange wood for next year remember the virus possibilities. Viruses such as Stony pit and yellow vein effect some fruits more than others. There are different strains of the illnesses. Bacteria such as Fireblight can completely wipe an orchard out. Some diseases damage fruits and prevent raising of sellable fruits. Next spring don’t graft anything you don’t need to to avoid spreading diseases but mark the trees you must graft this fall. There will always be diseases so don’t worry about it just decide how to handle it. Some diseases you may determine are bad enough to remove the tree. Few pear diseases are that bad but there are some out there. As you prune this year remember to use alcohol or bleach on your equipment between cuts so as not to spread diseases. Make notes on your heaviest bearing trees, time of year they produced etc. that will help with your spray schedule next year. Make sure to purchase dormant oil spray and copper if your like me and use them. See this article and this one

Since it’s that time of the year again I wanted to post a link that identifies most of the major pear pests again Pear: Fruit Development: Monitoring Pests and Their Damage—UC IPM. These are the several pages of fungal and bacterial diseases that pears and apples can get Not every disease or pest is in those 2 links but the common ones should be there.

@ltilton did you spray Fertilome after signs of fire blight? Did it work?

These black spots appeared on my pear pretty much overnight. Anybody know what it is?
-It’s been pretty wet here lately.


I didn’t have definitive signs of fireblight, I sprayed prophylactically. Can’t say if it worked but I didn’t have FB last year. Going to spray again tomorrow

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Those leaves dont look like FB to me. Keep a close eye out for any leaves that lose turgor, and look for a small droplet of golden ooze on green stems or leaf stems.


I agree looks like weather damage and not fireblight.


I have two young pears that have some type of canker on their trunks. I just noticed them this spring, they didn’t have these last year from what I can recall. One is a rescue pear and the other is a conference pear. They were planted in 2017.

The rescue pear has this canker and it is about halfway around the trunk. Some leaves may be showing signs of fireblight but the canker isn’t oozing like I’ve read fireblight cankers do.

The conference pear has this canker and it goes around maybe a quarter of the trunk.

So should I just completely remove these trees or cut below the cankers and hope I’m able to cut out all diseased wood, and let them regrow from lower buds?

I think this info from Penn State will help you decide what to do.

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Thanks for the link. Removing them seems to be the best option. I only wish I noticed them a month ago so there would be more options for replacements. There is a plant pathology and disease diagnostic lab here at UW-Madison, and I think I’m going to drop off some samples on Monday so I can determine if this is fireblight or something else.

Another canker question for all the pear experts here. This is a Blake’s pride pear planted in 2015 on unknown semi-dwarf rootstock from Stark bros. It has never flowered, but up until this year always had good annual growth and no signs of disease problems. This year the only buds that leafed out were on year old wood. All the buds and spurs on older wood died, presumably from cold injury (-30f). I’m finding lots of dead tissue and cankers on most branches, crotches, and the trunk. My best guess is original cold injury allowed pathogens to enter. Is there any hope for this tree or should I remove it. @clarkinks @mamuang your opinions are appreciated.

The bark low on the trunk is peeling away and tissue underneath is dead.

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So I sent twig samples to the plant disease diagnostic lab here at UW-Madison. The samples were from the rescue pear and Blake’s pride pear from the posts above. Both trees were negative for fireblight.

The cankers on the Blake’s pride were from Phomopsis, and the cankers on the rescue pear was Tubercularia which causes nectria twig blight. In both causes, they hypothesize that these funguses took advantage of tissue injury caused by our extreme cold this winter. In both cases they suggest pruning to remove. However I replaced both trees since the damage was so extensive.


Im not sure how i missed this post. Sorry to see these problems. Glad you figured out the cause of the problems. Removing the trees was the right thing to do. You were wise to eliminate these trees now and eliminate future problems.


I wasn’t so upset with removing the conference and rescue pears since they were only c couple v years old, but removing the Blake’s pride hurt a bit since it was more mature and I think it was beginning to spur up.

However looking on the bright side of things, I replaced the Blake’s pride with everyone’s favorite, harrow sweet. And the rescue and conference pears I replaced with Potomac and gem. Hopefully these prove to be more disease resistant and precocious.