What causes the pits/knots in my pears that makes them inedible?

February 14, 2023 Ask the Expert, Fruit Trees and Small Fruits, Managing Insect, Diseases, and Animal Pests

Question:

Last year many of our pear trees (we have about 10 varieties) had fruits with pits or knots in them making lots of the fruits nearly inedible. What causes this, and is there anything I can do to correct it?

I always prune my trees in the same way, and also thin the fruitlets early on. Do not fertilize or spray, other than applying ramial mulch around the base.

Answer:

Jonathan Foster, Community Education Assistant

I’m sorry to hear about your pear woes.

It’s difficult to diagnose pests and pathogens without photographs, but I’m assuming this time of year it may be difficult to provide those! Unfortunately, this one may be one I can diagnose without pictures. Stony Pit in pears (information with sample photos from Penn State Univ here and Michigan State Univ here) is a common ailment of the species, resulting in “dimpled” fruits that can be quite inedible, as you already noted. Plant pathologists suspect it is viral, though to my knowledge this has not been definitively established. The bad news, I’m sorry to say, is that management of the disease generally involves removal of the infected trees, as we do not yet have an effective treatment.

That said, similar symptoms can be caused by insect damage and boron damage, but we would need to submit a sample of the fruit to the UMaine diagnostic lab in order to be certain–unless it’s clear to you from the above resources that we have the diagnosis correct, I recommend getting back in touch with us next season when we can get an analysis performed for you.

I’m sorry not to have better news for you, but I wish you the best of luck with your other pear trees.