Elytroderma Needle Cast
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Contents |
Host
Ponderosa pine.
Distribution
Range of host in Idaho and Montana.
Damage
Witches brooms form in branches, and small trees are often deformed by loose brooming of the leader. Needles are infected yearly within the broom and are cast after 1 year. Growth loss, deformation, and occasionally death of small trees result.
Identification
New infections are started by spores in late summer. Needles are infected and the fungus grows into the twig and branch cambium. The witches broom, which forms after a few years' infection, combined with discoloration and shedding of needles within the broom, are good indications of this disease (fig. 81). Infection within the broom is chronic; the new needles are reinfected every year and are shed the following summer.
Branch infections are detected by cutting away the bark to expose the cambium. Small pockets of dark resin are distributed throughout the phloem adjacent to the cambium.
Fruiting bodies are black lines parallel to the needle axis at the lower end of needles (fig. 82). The fruiting bodies split the epidermis in mid to late summer to release spores.
Similar damages
Ponderosa pine dwarf mistletoe causes witches brooms which retain the normal complement of needles. The needles are green in dwarf mistletoe-infected brooms. Dwarf mistletoe plants are generally present as well. Other needle casts of ponderosa pine will cause discoloration but not brooming.
Comparison of Common Pine Needle Casts
| Primary Host | Symptoms | Fruiting Bodies | Fruiting Season | Needles Shed | |
|---|---|---|---|---|---|
| Lophodermella concolor | Lodgepole pine | Red-brown bands in summer and fall; entire needle tan in following spring | Tan cushions of fungus under flap of epidermis on tan needles | Late spring | 13 months following infection |
| Dothistroma pini var. linearis | Ponderosa pine | Distinct, red, transverse banding at random on needles; needles become tan in fall or spring following infection | Black dots in red bands | April-November | 15-24 months following infection |
| Dothistroma pine var. linearis | Western white pine | 1-year-old or older needles turn red or brown. Red transverse banding indistinct or absent | Black dots breaking through epidermis | April-November | Needles remain attached, drooping on twigs for 1-2 years following infection |
| Elytroderma deformans | Ponderosa pine | Needles gradually turn red-brown. Part of needle may remain green. Witches brooms. | Black slit in epidermis near base of needle | Mid-to late summer | 12-20 months following infection |
| Lophodermella arcuata | Whitebark pine, limber pine | Black lines on dead needles | Late spring | 13 months following infection |
References
Anonymous. 1982. For. Insect & disease identification and management. USDA For. Serv.,Northern Region; Idaho Dept. of Lands, Insect and Disease Control; Montana Dept. of State Lands, Division of Forestry. 192 p.
Bega, R. V. 1978. Diseases of Pacific Coast conifers. USDA For. Serv. Ag. Hndbk. No. 521, 206 p.
Hepting, G. E. 1971. Diseases of forest and shade trees of the United States. USDA For. Serv. Ag. Hndbk. No. 386, 658 p.
Field Guide to Diseases and Insect Pests of Idaho and Montana Forests, USDA Forest Service Northern Region, Publication Number R1-89-54
