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Disease Note.

Pine-Pine Gall Rust, Caused by Peridermium harknessii, on Scots and Ponderosa Pines in Missouri. F. Rycyk, Jr., Missouri Department of Agriculture, Jefferson City 65102. C. J. Luley, and P. Gowen Overton. Missouri Department of Conservation, Jefferson City 65102, and Avila College, Kansas City, MO 64145. Plant Dis. 73:610. Accepted for publication 22 April 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0610B.

In 1984 and 1988, rust galls were found on ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws.) and Scots pine (P. sylvestris L.), respectively, near Columbia, Missouri. Aeciospores collected on 19 May 1988 from galls on both pine species were allowed to germinate on water agar in darkness for 24 hr at 18.5 C, and the germ tubes were examined for the morphological characteristics by which Peridermium harknessii J. P. Moore (= Endocronartium harknessii (1. P. Moore) Y. Hiratsuka) (2) may be distinguished from Cronartium quercuum (Berk.) Miyabe ex Shirai (I). Germ tubes from both sources conformed to the reported behavior of P. harknessii. The mean length was 245 !lm, 23% were branched, 95% of branches occurred in the proximal half of the germ tube, and the tips did not lyse. This is the first report of pine-pine gall rust in Missouri. This rust is a potential threat to Christmas tree and other plantings of Scots pine in the state.

References: (I) G. W. Anderson and D. W. French. Phytopathology 55:171, 1965. (2) Y. Hiratsuka. Can. 1. Bot. 47:1493, 1969.