Stony Pit

Overview

• Stony pit is caused by a destructive virus that is transmitted by virus-infected pear wood (rootstocks, buds, or shoots).
• Symptoms of stony pit are severe dimpling/pitting/discoloration of fruit that can make the fruit unsightly and/or unmarketable.
• Stony pit can affect all pear varieties (European and Asian), however, it seems to be most prevalent in the variety Bosc.
• Control of stony pit is only provided by using certified virus-free rootstocks, trees, and budwood.

Symptoms & Signs

Stony pit first appears as dark green areas on the pear fruits beginning as soon as three weeks after petal fall. Fruit growth is restricted, resulting in dimpling, pitting, gnarling, and deformed fruit. It can be similar and confused with plant bug/stink bug injury, however, stony pit is typically more severe in damage. In fact, the fruit can be severely stunted, gritty, difficult to cut, and measles-like in appearance. Sometimes tree symptoms are observed including pimpling/cracking of bark, stunting of trees, and chlorotic vein-banding or mottling of foliage. (Typical virus symptoms.) Symptoms can appear one year and not the next, although may again show up anytime on the infected pear tree.

Disease Cycle

The virus that causes stony pit is only transmitted by vegetative propagation with infected wood/cuttings/buds. It is apparently not transmitted by insects or seed.

Chemical Control

There is none.

Fungicide Resistance in the Eastern U.S.

NA

Non-Chemical Control

Biological Control

Cultural Control

Achieved by using only (certified preferably) virus-free wood/buds when grafting, budding, etc.  Infected trees should be removed from the orchard, although Bartlett (which is symptomless) could be top-worked onto infected trees.

Resistant Varieties

Bosc, Seckel, and Comice seem to be the most severely infected varieties, although all pear varieties (including Asian) are susceptible to having the virus and displaying symptoms. Bartlett appears to be a symptomless carrier of the virus.

Links

http://extension.psu.edu/plants/gardening/fphg/pome/diseases/stony-pit

http://postharvest.tfrec.wsu.edu/marketdiseases/pearstony.html