Red growths and curling leaves on pear

Asked April 6, 2018, 12:34 PM EDT

Hello, Yesterday I noticed red bumps and curling leaves on our European pear flower clusters (dwarf Orcas variety). I picked off the affected clusters or individual leaves. About 10-15% of the leaves/clusters were affected. It's a fairly young tree, maybe 3 or 4 years old. What is causing the bumps and curling, and what treatments are available? How can we prevent spread to the unaffected leaves if it's too late to treat this year? Thanks so much!

Benton County Oregon horticulture

1 Response

Those symptoms are the result of eriophyid mites, which are too small to be seen without magnification. Here is a link to a complete description of the pest, damage, and management options...

A dormant application of lime sulfur generally is effective, but lime sulfur is not available in smaller than 2.5-gallon quantities. It can be used on many types of fruit trees, so if you have more than just a couple of fruit trees, a 2.5-gallon container may not be as impractical as it sounds (cost is about $35). I generally recommend a combination of lime sulfur and dormant oil, but the oil can also be applied by itself. Thorough coverage of all twigs, branches, and bark is essential.

I suggest avoiding carbaryl, as it has been known to disrupt natural predators such that spider mite outbreaks become more likely. Therefore, sulfur is the only option remaining for home use during the growing season; it may cause russeting of some varieties, but on such young trees that shouldn't be a major issue (i.e. not much fruit to worry about yet).