Alaska Pioneer Fruit Growers Association

Spindle Galls on Local Tree

December 23, 2005

By Tom Marshall

 

In July strange growths were found on the underside of some of the leaves of my four year old native American plum tree. Each one looked like a little cigar shaped dark green tubular leaf on a small lighter green stem.  They ranged in length from1/4 to 3/4 inches.  I brought some affected leaves to Tami Schlies’ orchard tour on June 22 and the members present, representing a wide distribution of orchard experience, had not seen this type of gall.

 

Later an entomologist with the USDA found a very small white larva in one of the galls and showed it to me.  It was only about 1/250th of an inch long, but was clearly visible wiggling away under a 50 power binocular microscope.  A plant pathologist found a colored picture of a sugar maple leaf with galls that looked identical to the galls on my plum tree.  They were called spindle galls and were caused by the insect Verates aceriscrumena.

 

A possible connection between the maple and the plum tree might be that my plum tree was purchased from a New York State nursery, a maple sugar producing area. Once the affected leaves were picked, the galls did not spread and the plum tree is very vigorous. I will gather and burn all plum leaves this fall.  I also froze some of the specimens on the leaves they infected for future research.