Spotted leaves, Pear Tree

Asked April 20, 2020, 5:30 PM EDT

We’ve just planted a couple Bartlett pear trees a few weeks ago. Now the leaves are beginning to come out after blooming and one branch has rusty spots on it. Could be pear rust? Just wondering if they should be sprayed right away, maybe removed before it spreads to more branches? Thank you for your help!

Multnomah County Oregon

1 Response

The speckled, slightly raised areas are caused by pearleaf blister mites (Eriophyes pyri), a common problem for pears, especially 'Bartlett' and 'Anjou' during a particularly moist, rainy spring. These mites are far different than the spider mites you may be familiar with. They are microscopic.

Affected leaves may drop prematurely. Loss of foliage weakens the trees, reduces shoot growth, and interferes with fruit maturation and fruit bud formation. But because the trees were just planted, it's a wise idea to avoid fruit set for at least 3 years. Doing so will allow the trees to establish a sturdy root system.

A spray won't help this season because the damage is already done. Our official plant disease handbook suggests "Plan on taking action the following fall or spring. . ."

"Lime sulfur - Applications in the fall can significantly reduce populations. . . the following year." {But you likely will have problems finding a retail source for home gardens. You might try local farm stores.)
- "Superior oil - Apply in the spring as buds begin to swell."