Spots on pear leaves

Asked April 21, 2018, 8:51 PM EDT

Hi, my new pear tree has spots and the leaves are curling. Since the weather has been very wet, I'd guess it's a fungus. How do I treat it? Thanks, Louise

Benton County Oregon

1 Response

Thank you for including the images aas they are helpful diagnosing the damage.

The spots on the pear leaves are caused by pear leaf blister mites, sometimes referred to as pear rust mites. They are eriophyid mites and are far different than the spider mites you may be familiar with. Spider mites are about a 32nd of an inch, somewhat oval, and have 8 legs. Pear leaf blister mites are smaller, elongated (similar to a worm), and have only 4 legs.

Blister mites survive the winter under the scales surrounding the flower buds where they begin feeding before bloom. Feeding causes reddened raised areas on the leaves which, with time, become brown. The mites may also feed on the fruit’s skin.

Home gardeners can decrease the mite populations by applying lime sulfur in the fall. (Unfortunately, lime sulfur may be difficult to locate in small packaging suited for home garden use.) In the spring, prior to bud swell, either repeat the lime sulfur or use superior oil. Follow label directions as to the dilution rate.