Nursery disease problems - Sirococcus strobilinus

Sirococcus strobilinus is a major problem in the Jeffrey pine and ponderosa pine at the Humboldt Nursery located 300 miles north of San Francisco, on the California Coast. This disease has also been found infecting sugar pines at Humboldt Nursery and coulter pine at another nursery on the California Coast 90 miles south of San Francisco, but it has not caused a problem in these species. SYMPTOMOLOGY -- This fungus causes a tip dieback of the current years' growth in nursery-grown pine seedlings. The various stages of the disease seen in the field suggest that initial infection occurs in the juvenile needles. From these it spreads down into the succulent stem tissues, where it causes a small purplish canker. The canker enlarges, growing longitudinally up and down the stem more rapidly than around the stem, producing an elongated sunken canker. A small drop of resin is often exuded in the central area of the canker at the needle base where infection first entered the stem. At this stage in canker development, small black pycnidia begin to appear on the dead needles and the older portions of the canker. When infection occurs in the region of elongation, the restricted growth in the cankered area causes the shoot tip to curl over and form a crook. Ultimately, the canker girdles the stem, and the tip distal to the canker dies and turns brown. Infection appears to be confined to the current year's succulent growth.

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Details

Author(s): Michael D. Srago

Publication: National Nursery Proceedings - 1978

Event: Nurseryman's conference and seed processing workshop
1978 - Eureka, CA