Cause Pucciniastrum epilobii f. sp. palustris, a fungus, has been reported from Oregon and Washington. It also infects fireweed (Epilobium sp.) and true fir (Abies spp.). On fir it produces yellowish, tubular aecia on current-year true fir needles that mature several weeks before P. goeppertianum. Spores produced on fir infect only fuchsia or fireweed. Older fuchsia leaves are more susceptible, and low light favors disease development. The rust can overwinter and maintain itself in the uredinial state independent of alternating to true fir.
Symptoms Pale or yellow spots develop that may progress rapidly to tan or brown necrotic spots or blotches. On some cultivars, spots may be on only a few leaves or have purple borders. Small, yellow to reddish fruiting bodies (uredinia) develop in irregular groups along the margins of necrotic spots on the undersides of the leaves but are easily overlooked. Severely diseased leaves dry up and drop off. Defoliation weakens plants, which may recover or die.
- If practical, remove the true fir alternate host from in and around the greenhouse or growing area. Removing fireweed also may help.
- Remove and destroy all fallen or infected leaves.
- Plant resistant cultivars or widely separate from susceptible cultivars.
- Keep the foliage dry, and space plants for good air circulation.
- When transplanting do not cover the root crown with excessive media or soil. Transplant back to the original soil line.
Chemical control Use when symptoms are first found on alternate hosts.
- Eagle 20 EW at 6 to 12 fl oz/100 gal water. Group 3 fungicide. 24-hr reentry.
- Mancozeb-based products. Group M3 fungicides. 24-hr reentry.
- Fore 80 WP at 1.5 lb/100 gal water plus a spreader-sticker.
- Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker.
- Myclobutanil 20 EW T&O at 6 to 12 fl oz/100 gal water plus spreading agent. May observe a PGR effect. Group 3 fungicide. 24-hr reentry.
- Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens at 1 fl oz/gal water. Group 3 fungicide. H
- Terraguard SC at 2 to 8 fl oz/100 gal water. Group 3 fungicide. 12-hr reentry.
Reference Loring, L.B. and Roth, L.F. 1964. Pucciniastrum epilobii on fuchsia in Oregon. Plant Dis Rep 48:99.