Hard black spots on core and sides of pear

Asked August 25, 2015, 6:26 PM EDT

Our Bartlett pears are very yummy. However, most of them have very hard black spots in the core and outer layer of the pear. What has caused this and what can we do to avoid this in the future?

Pierce County Washington

1 Response

It sounds like it could be Stony Pit Virus. A virus called stoney pit can be one of the problems but other things can look like this. Symptoms may be confused with pitting from tarnished-plant bug damage, stink bugs, boron deficiency, or corky spot. Depth and shape of the corking spots will give you clues as to the problem. Boron deficiency spots tend to be square and flat bottomed (like you pressed the flat part of a nail head into the pear flesh), cork spot would show spots deeper than a stink bug could reach with its mouthparts (1 cm or less from the surface). Stink bug cork spots are shallow and have irregular shape (but not square). It is a depressed blemish with a puncture site that is always visible in the center leading to a brown cork-like area in the flesh.

Too much information? Try cutting the pear open. If you cut open the pear through one of the deepest dimples and fond a very hard raised brown knot (hard like a peach pit), it's probably Stony Pit virus. If you cut though the dimpled area and it's just a shallow non-hard brownish area, it's probably bug damage.
If you believe it's stony pit virus, your only real solution is to remove the trees and replace them with CERTIFIED virus-free trees. You may want to take in one of your pears to your Master Gardener Plant Clinic for confirmation of a different diagnosis. I wld ould definitely do that before taking drastic action.

Here is information from PNW Handbooks: http://pnwhandbooks.org/plantdisease/node/3668/print and pictures of what the "stony pit" area looks like in the pear with the virus: https://agdev.anr.udel.edu/weeklycropupdate/?p=3596