Damage, symptoms and biology
This disease is the most common and most destructive needle cast in fir. It severely defoliates seedlings and young trees, reduces their growth, and may sometimes kill them. In larger trees, however, the damage does not cause any serious problems. The current year's needles are infected first, but they do not show any damage. The following spring, brown spots appear and spread, eventually covering the entire surface of the needles by mid-summer. The first fruiting bodies form on the upper surface of the needles and discharge spores in late summer or early fall. It is unclear just what role these spores play, but they may give rise to the second type of spores. Ascospores form in mid-summer on the needles infected two years earlier. Hysterothecia, the fruiting bodies bearing these spores, create a black line on the underside of the needles. This line is actually the ascus, which will release ascospores able to infect new shoots the following spring.
No measures are implemented to control this disease in the forest. With high-value trees, however, pruning of affected branches represents a good means of suppression. The disease causes considerable damage in Christmas tree plantations. Fungicide spraying may also be effective, but it must be done at the right time, that is, when the spores are released. To find out about the registered products available for use against a particular insect or disease, please contact the Pest Management Information Service of the Pest Management Regulatory Agency (PMRA), at the following toll-free number: 1-800-267-6315.
Canadian Forest Service Publications
Information on host(s)
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