Fig. 1 (above)
Stolon of a rust-infected plant. Holes in the leaves were created by insects and do not necessarily indicate rust is present. Rust damage is seen as small spots on the leaf surface and as blackened areas of the leaf. Small lesions are also present on the leaf stalk (petiole).
Fig. 2 (above)
A variety of leaves showing increasingly severe rust symptoms. Holes in the leaves were created by insects. Rust lesions on the top side of the leaf are small brown dots. As infection progresses, they expand into larger spots. On the underside of the leaf, clusters of spores are produced either in the center or around the edges of these spots (see Fig. 3). In a severe infection, segments of the leaf become blackened and dead and ultimately a whole stolon may be killed.
Fig. 3 (above)
Sori caused by Puccinia glechomatis on underside of ground ivy leaf. This leaf shows a blackened segment caused by the rust and later nibbled by insects. At the bottom, center, is a tan-orange ring of rust teliospores surrounding a blackened area. Under a hand lens the rust sori appear minutely furry and are slightly raised from the surrounding tissues. Two lesions in the green tissue near the top left are also caused by the fungus.
Fig. 4 (above)
Spores of the rust fungus at high magnification. A microscope is needed to see these beautiful spores, which are found on the undersides of the leaves in tiny structures called telia. No other spore stages are known for Puccinia glechomatis (i.e. the rust is microcyclic).
Photographs by K.T. Hodge and K. Loeffler, © Cornell University 2001.