Can you identify my problem with my pear tree? Every year the pears when...

Asked July 11, 2014, 1:02 PM EDT

Can you identify my problem with my pear tree? Every year the pears when forming on the tree get these black spots to the point of almost covering the entire pear. What may I do to correct this? The variety of pear is the "Parker Pear". Thanks, Bill

Anoka County Minnesota

7 Responses

Thank you for your question.

According to our own U of M trees.umn.edu, Pyrus 'Parker's Pear' is susceptible to various diseases: "Very susceptible to fireblight, particularly in years with warm and wet spring weather. Additional disease problems include anthracnose, canker, scab and powdery mildew." Other pests include pear psylla, coddling moth and borers.

Because you said this occurs every year, I am thinking this is a disease issue and your tree is susceptible to the disease.

To help zero in on the disease, can you please provide more info about the black spots? For example, can you wipe off the black splotches> Are they raised? Rough? or smooth? Is the inside of the fruit damaged?

Also, how is the rest of the tree? It looks like you have some leaf damage - how about leaf drop / discoloration? Any dark areas on the branches? Cracks? Dieback?

Please reply to this email. Looking forward to hearing more about your tree.

Hi Julie;

The black blotches on the fruit are neither raised nor rough. The inside of the fruit seem to be ok and edible but I haven't eaten any over the years for fear of not knowing what it is.

The leafs are discolored as well but the bark and branches seem ok. The leaves do not drop.

Bill

Thanks Bill for the follow up. Can you wash or wipe off the black blotches?
If so, I wonder if this is mildew or sooty mold. I've sent on your question to our extension plant pathologist to see if she can advise.
Thanks for your patience.
jw

Hi again Julie:
The black splotches will neither wipe or wash off. It is like they are "etched" into the pear.
Thanks, Bill

Hi Bill:
I have searched high and low for an answer for you. I think it's a disease causing this problem (vs. an insect) that your pear is susceptile to since it occurs annually. I thought maybe it was mildew because doesn't affect the inside of flesh of the fruit or cause the scabby rough skin of apple scab. But I can't be sure and I think it would be a good idea for you to send in a sample to the University's Plant Disease Clinic. Because this occurs every year and because your variety is susceptible to so many things, it would be good to get a diagnosis from the clinic. It costs about $45 and is ultimately your choice of course, but the trade-off would be a healthier tree and fruit you could potentially harvest and enjoy.

The Plant Disease Clinic has a website with instructions for submitting a sample: http://pdc.umn.edu. I'm sorry I couldn't help you more, but we just don't have a lot of information on pears even though the U has bred varieties for Minnesota gardens. If you do decide to submit a sample, I'd appreciate if you'd drop me an email with the results: weise019@umn.edu.

Best of luck and thanks for contacting Ask an Expert.

Hi Bill:

I just heard from our extension plant pathologist and she confirmed your pear does indeed have pear scab. Here is what she said:

What he is describing sounds like pear scab. It is caused by a different species of fungus than apple scab (Pear scab is Venturia pirina, and apple scab is Venturia inaequalis) but the biology of the pathogens and the diseases they cause are very similar. The fungal pathogen will overwinter in infected leaves below the tree and in the spring spores are released to infect young leaves. These leaf infections then produce spores that infect fruit and other leaves and the cycle continues all summer when warm wet weather occurs. The corky black lesions on the fruit do not make the fruit inedible. They could be peeled and eaten. In some cases the infection is so bad that the fruit becomes cracked or misshappen. In this case he might see secondary rot organisms coming in and of course those fruit would need to be discarded. It is too late to prevent new infections this year but he can use the management options listed in the IPM for home apple orchards pub for apple scab (http://www.extension.umn.edu/garden/yard-garden/fruit/apple-pest-management/ ) to decide what to do this fall and next spring. He should be aware that although the same fungicides for apple scab should be effective against pear scab, the pesticide label would have to specify for use on 'pear' or he could not use it.

So ... treat this fall and next spring with fungicides labeled for "pears" for scab. Also be sure to rake and clean up fall leaves and fruit to reduce habitat for the fungal spores (a good overall practice for garden care).

Thanks for your patience, Bill, and for contacting Ask an Expert. Best of luck with your tree.


Julie;
Thank you and your plant pathologist for working so hard on this. I will treat for "Pear Scab" this fall and next year. If I have the same problem next year I will submit a sample to yoir clinic for diaqgnosis.
Thanks again
Bill