Plant Disease Management Handbook

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Bracken Fern (Pteridium aquilinum)

Sword Fern (Polystichum munitum)

Cause Powdery mildew is a common disease caused by several Erysiphe species. The fungus E. pseudopusilla is the only species reported in the US on the plant E. americanus. Species reported on Euonymus japonicus include E. euonymicola and E. lianyungangensis in other parts of the world.

Cause Rhizobium radiobacter (formerly Agrobacterium tumefaciens), a soilborne bacterium, enters Euonymus plants through wounds, either natural or caused by pruning, grafting, mechanical injury from cultivation, heaving of frozen soils, chewing insects, or the emergence of lateral roots. Pruning tools that cut through galls can become contaminated with the bacteria and spread them to cut surfaces of subsequently pruned plants.

Cause Pseudomonas syringae pv. syringae, a bacterium. Factors that favor the disease include wounds, frost damage, soil pH, poor nutrition, and infection by other pathogens. Sources of bacteria include old cankers, healthy buds, and epiphytes on leaf surfaces, weeds, grasses, and even soil. Bacteria can spread by wind, rain, insects, and infected nursery stock.

Cause The fungus Colletotrichum gloeosporioides has been found a few times by the OSU Plant Clinic and is considered an occasional problem in BC. It is a problem on Euonymus japonica and E. fortunei including the very susceptible cultivars Canadale Gold, Emerald Gaiety, and Emerald 'n Gold. The fungus is favored by warm temperatures and long wet periods.

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California Poppy (Eschscholzia californica)

Cause The fungus-like microorganism Phytophthora cinnamomi has been reported and found frequently in Oregon. Waterlogged soils and warm temperatures favor P. cinnamomi. It survives unfavorable periods in soil and infected plant debris. Under favorable conditions, spores germinate and infect roots. After infection, the microorganism spreads mainly in the inner bark tissues of the root and stems.

Cause Nectria cinnabarina, a fungus. It is a common saprophyte on many plant species. The fungus colonizes bark, cambium, and sapwood of stems weakened by freezing, drought, mechanical injury, or other diseases.

Cause Ophiostoma ulmi (formerly Ceratocystis ulmi) and O. novo-ulmi, fungi with many subgroups. The first of two North American epidemics began in the 1920s with the introduction of a relatively non-aggressive subgroup, which reduced the native elm population. A second, more destructive epidemic began in the 1940s with the introduction of a more aggressive subgroup, which has been found in Oregon.

Cause Wetwood is associated with bacteria including Enterobacter nimipressuralis, Bacillus megaterium, and Pseudomonas sp. Liquid accumulates in diseased tissue of the tree which is then colonized by the bacteria. Anaerobic growth of the bacteria produces gas inside the tree. The high gas pressure forces liquid out of the tree where it dries on the bark. A higher pH also can be detected in diseased tissue.