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Leaf galls

Leaf galls are widespread this year on maple, plum, oak and many other tree species. The structures resemble tiny beads, bladders, fingers, or spindles; others are flat hairy patches; and others cause leaf edge swellings. Galls vary from green to red in color.

Leaf galls

In the spring, tiny mites that overwinter on the bark crawl onto developing leaves and initiate increased production of normal plant growth hormones that guide gall formation. Mites feed and reproduce inside these galls. Most all leaf galls are caused by mites. Larger leaf and twig galls of various shapes are caused by insects such as wasps and psyllids. Death of individual leaves seldom occurs, but the number of galls per leaf may become so unsightly that control is desired on ornamental trees.

Leaf galls

Spring application of a miticide seven to ten days before budbreak, again when the leaves are beginning to develop from leaf buds, and a third application seven to ten days later can greatly reduce gall numbers. A l996 Minnesota Extension Service publication, FO-6704-S, titled "Insect and Mite Galls in the Landscape", provides more information on these gall makers.


Aphids, aphids, aphids

Sapsucking aphids have been very active in forest stands and yard trees this spring, likely brought on by the warm, dry weather in April and early May. Aphid species on white spruce and Norway pine have been reported throughout the Northwest Region. While sampling branches for spruce budworm, spruce aphids were often observed associated with branches dripping small amounts of pitch from aphid feeding wounds on the twigs, especially in stands of large crown trees that were closely spaced. In early May, stands of white birch in Beltrami County were noticed to have a "shiny" glaze as if sprayed with a polyurethane coating. This coating was "honeydew" excreted by the aphids. If you had parked your new Cadillac under these trees for a few hours the presence of aphids would have surely been noticed.