Pine Needle Rust

By The Old House Web

Pine Needle Rust

Pine needle rust, caused by Coleosporium asterum, is a common disease in the north central states, but it seldom causes serious damage. The needle rust kills older needles on seedlings and younger trees up to the sapling stage, primarily on red pine but also on Scotch and jack pine. In spring, infected trees will show browning of the lower needles on the trees. With the onset of spring, orange droplets appear on infected foliage, and by late May and June, orange blisters become evident. The blisters, which may resemble pine needle scale, are masses of spores that cannot infect other pines. Instead, the spores infect the leaves of asters and goldenrod in early summer. By late summer, orange spores have formed on the undersides of the lower leaves. In cool, wet weather in late summer and into fall, a second set of orange spores on the undersides of aster and goldenrod leaves are carried by winds to pine needles, where they cause new infections.

Control: Attempts should be made to eradicate asters and goldenrod in the immediate vicinity of the nursery or planting. Controlling other weeds will also help increase drying of the lower foliage following rain or dew. Keeping foliage dry is very effective in inhibiting infection by the spore. No recommendations for chemical control have been developed and no chemicals are currently registered for control of pine needle rust.

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