In August 1998, The Plant Disease Information Office started to receive an unusual number of phone inquiries and samples of ailing white pines from throughout the state. The symptoms on the trees were distinctly different from those associated with diseases of white pine previously reported in Connecticut. After extensive microscopic examination and search of the literature, the disease was identified as Canavirgella Needlecast. This disease has never been reported for Connecticut although it is thought to be present along the eastern seaboard, from North Carolina to Maine. The first report documenting the association of the fungus Canavirgelia banfieldii with this needlecast disease appeared in 1996.
SYMPTOMATOLOGY AND DISEASE CYCLE:
This needlecast, caused by the fungus Canavirgella banfieldii, is a disease of Pinus strobus (Eastern white pine) and Pinus peuce (Macedonian white pine). Infected trees appear distinctly reddish brown from a distance in late July and early August. Upon close inspection, the symptoms are usually confined to current-season needles. Tips of infected needles first appear yellowish tan and develop a distinct reddish brown color by late August. By the following spring, infected needles curl and fade to tan or gray. One of the diagnostic characteristics of the disease is that not all needles within a fascicle are infected. Additionally, individual needles within a fascicle may exhibit differing amounts of symptomatic tissue. When needles are infected with Canavirgella, the bases of the symptomatic needles usually remain green and the needles and the fascicle often remain attached to the tree. Symptomatic portions of individual needles may break off before the fascicles drop during periods of normal needle shedding. The general symptoms of this needlecast have frequently been confused with those associated with acute ozone injury and other needlecast diseases. However, with ozone, symptoms usually develop on all of the needles within a fascicle and needles exhibit the same extent of injury.
Infection of succulent, elongating current-season needles apparently occurs in late June or early July. The spores (ascospores) of the fungus are thought to be released during early stages of needle elongation and during periods of favorable weather. As with most needlecast pathogens, extended periods with free water on the needles are conducive for infection. The disease does not appear to be site-specific since heavily infected trees have been found on warm, exposed south-facing slopes as well as on cool, moist, north-facing exposures.
As with most needlecasts, control of Canavirgella needlecast can be achieved using a multifaceted approach. This disease can often be effectively controlled by following good sanitary and cultural practices. Tree vigor should be maintained by proper watering, fertilizing, and pruning. Although needlecasts are usually considered to be more aesthetic than life-threatening and are rarely serious enough to warrant chemical control, there are situations where they can be serious and cause permanent damage, disfigurement or even tree death. Newly transplanted trees or trees weakened by stress are particularly sensitive to repeated premature needle drop. In such cases, chemical control should be beneficial. However, once symptoms are visible on the needles it is too late for chemical applications. Because of the newness of this disease to Connecticut, specific fungicides are not labeled for use. Information on the efficacy and timing of fungicide applications will be forthcoming.
Dr. Sharon M Douglas, Department of Plant Pathology and
Ecology, The Connecticut Agricultural Experiment Station,
123 Huntington Street, R 0. Box 1106, New Haven, CT 06504 email: sdouglas@caes. state. ct. us
This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.
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