Crop Knowledge Master Fungi

Fusarium proliferatum

Leaf and sheath spots of orchids
Damping-off and root rots of orchids
Flower spots of
Young cane blight of
Hosts Distribution Symptoms Biology Epidemiology Management Reference

TYPE: Kingdom: Fungus

Phylum: Ascomycota (teleomorph or sexual state)

(Hypocreales, Hypocreaceae)


Traditional: Fungi Imperfecti: Deuteromycotina

Hyphomycetes (anamorph or asexual state)

(Hyphomycetales = Moniliaceae + Dematiaceae)

Form genus: Fusarium


TAXONOMY: Fusarium proliferatum is the asexual state or anamorph. The sexual stage or teleomorph that produces ascospores is not known for this species. Fusarium spp., closely related to F. proliferatum, have Gibberella teleomorphs.



Leaf and sheath spots of orchids

Damping-off and root rots of orchids

Flower spots of Dendrobium

Young cane blight of Dendrobium



Orchids, such as Dendrobium and Cattleya.


DISTRIBUTION: Cosmopolitan. Common on dendrobium and other orchids in Hawaii.



Various parts of orchid plants are attacked by this fungus. The most serious disease caused by F. proliferatum on orchids is damping-off and rots of young plants. Hundreds of young seedlings are lost in community pots due to this devastating disease. Rots of these plants kill many and stunt the growth of survivors. As surviving plants mature they are plagued by the recurrence of fusarial diseases during wet periods.

On dendrobium plants at least 9 months old, new shoots are blackened by Fusarium infections and slow rots develop especially at the leaf tip. Leaves are lost and the entire apical tip of new shoots are commonly killed. Fusarium proliferatum causes small (2 - 5 mm) circular to oval spots with irregular edges. Spots expand very slowly. As the leaf matures, some of the spots develop a black edge, while the center of the spots becomes sunken. The leaf tissue surrounding the spot is slightly chlorotic or pale green.

With mature dendrobium plants, only the young leaves or wounded leaves are susceptible, while mature unwounded leaves are resistant. The occurrence of leaf spots on mature leaves is the result of infection when leaves were young. The distribution pattern of leaf spots reflect the leaf position of the unopened, young leaves of a new shoot. A characteristic pattern of spots for this disease is a row of spots across the width of the leaf (Fig. 1). Sunken brown spots also occur.

The fungus infects the leaf sheath causing black to dark brown rots with irregular edges. Rots expand very slowly and after a few months, the center of sheath blights or rots can be white to tan.

Circular to elongate spots also develop on flowers. Spots are tan to deep brown with a dark border (Fig. 2).

On cattleya hybrids, elongated black rots on new leaves or blackened sheaths of young shoots are caused by Fusarium proliferatum.




Fusarium proliferatum produces microscopic, long, canoe-shaped spores called conidia. These asexual conidia have 3 to 7 cells and are produced on specialized hyphae called conidiophores. A second, smaller type of conidia with 1 or 2 cells, called microconidia are also produced. Both spore forms are produced in very large numbers (millions) and germinate on suitable substrates, such as the host and grow into a colony which produces more spores.

Growth of Fusarium is favored by moisture and temperatures in the range of 25-31 C.




Fusarium proliferatum produces many spores on the surface of infected host tissue. Some microconidia are also produced within rotting tissue. White cottony masses on the diseased tissue are spores and mycelia of the fungus. These spores are blown or splashed to nearby plants or other healthy tissue. For many orchid plants such as dendrobium, new shoots are formed below the canopy of the older leaves. Thus fungal spores formed on older shoots easily splash or drip on young shoots emerging from the base of the plant.

Young shoots are very susceptible to infection and rapid disease development. Likewise, fragile young plants in community pots are extremely susceptible to this fungus and many are killed. Since growers commonly salvage all plants that survive, the Fusarium will persist on mature plants and cause leaf, sheath, shoot, and flower rots. These plants serve as sources of inoculum, and disease spread within a greenhouse is insured by overhead watering.

Fusarium spores are distributed by wind, splashing water or the movement of spores by contact (hands, clothing, gloves, etc). Insects, snails, and slugs also move spores from diseased to healthy plants. Fusarium will survive in diseased plant tissue for many months and spores will also survive in potting media and in the immediate environment of the diseased plants. Greenhouse walls, benches, floors, etc. will be contaminated as long as diseased plants are present.




It is nearly impossible to eradicate Fusarium once it has infected an orchid plant. Thus great emphasis must be placed on keeping young, disease-free seedlings healthy. The production of new seedlings should be in a greenhouse separated from the production of mature plants. This seedling-house should not have any mature plants of any kind, especially samples of mature blooming plants.

Those community pots removed for exhibition or sales from this clean seedling-house, and maintained (transported, displayed, etc) with mature plants, should not be returned to the seedling house. The risk of contaminating the seedling-house is not worth the savings from of a few pots. Keep these seedlings outside the clean seedling-house.

All diseased leaves, dead shoots and infected flowers need to be gathered and discarded from the nursery. Do not drop infected material to the ground as this provides the fungus a good opportunity to infest the ground for long periods.

Spores of Fusarium, like those of many pathogens, need water to germinate and penetrate the host. Thus controlling moisture will reduce disease levels. Avoid watering in the early evening as this will expose leaves to a long period of wetness during the night. Water during the day and keep leaves are dry as possible. Increase air movement to reduce humidity levels. Remove weeds and other shrubs that prevent adequate air movement.

Fungicides such as Dithane M45 will also reduce infection levels.





Hawksworth, D. L., P. M. Kirk, B. C. Sutton, and D. N. Pegler. 1995. Ainsworth and Bisby’s Dictionary of the Fungi. CAB International. University Press, Cambridge, Oxon, U.K.


Nelson, P. E., T. A. Toussoun, and W. F. O. Marasas. 1983. Fusarium species: An illustrated manual for identification. Pennsylvania State University Press


Uchida, J. Y. 1966. New developments in fungal pathology on ornamentals. Floriculture Production Seminar. Sept. 1996. Honolulu HI.



COPYRIGHT: Janice Y. Uchida




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