Infected needle symptoms are normally seen the following late winter or early spring. Spores of the causal fungus, produced in tiny, black, football-shaped structures in infected needles, are spread by wind and infect current needles during moist periods from August to October. By late summer, only tufts of green current-season needles may be left. Needles initially turn yellow, then brown, and are shed throughout the summer. In late autumn, small, brown spots with yellow halos appear on the current-year foliage. In Christmas tree plantings, short-needle varieties of Scots pine with seed origins from Western Europe (especially France and Spain) are particularly susceptible. Lophodermium seditiosum, the causal fungus, can cause the greatest needle cast damage among Scots pine, and red pine trees. Needle blight diseases normally present themselves in shaded parts of plantings on the lower branches, and also on the northern sides of individual trees. Due to there being different timings of management activities for each disease, it is important for growers to identify the problem correctly. Three important needle blight and needle cast diseases affect Scots pines, especially within North American Christmas tree plantations. Scots pines are widely grown as Christmas and landscape trees. Although most conifers are somewhat susceptible to needle cast diseases, certain varieties of Scots pine, Douglas-fir and Spruce growing in locations favourable for disease may be severely affected. Severe cases of needle drop not only decrease tree value, but result in poor tree health and vigour. MISC0186.Christmas tree growers are advised to be on the lookout for needle infections by fungal pathogens causing discolouration and defoliation. Washington State University Cooperative Extension. Christmas Tree Diseases, Insects, and Disorders in the Pacific Northwest: Identification and Management. Applying chlorothalonil-based products may cause chlorotic or necrotic needle flecking. May take 1.5 to 2 years before benefits are realized. Not needed in harvest year, especially for clearcut operations. Control weeds around the bases of trees.Ĭhemical control Apply twice when needles emerge and new shoots are expanding, starting 4 years from expected harvest.Remove standing timber immediately adjacent to Christmas tree plantations.Do not interplant the next rotation before the current rotation of trees has been completely harvested.If fungi cause the disease, then practices that increase air circulation and needle drying will be beneficial.Small, black, fruiting bodies (pycnidia, pseudothecia, or perithecia, depending on the fungus), develop on needles' undersurfaces in spring when they begin to abscise. Needles abscise and fall off by the following spring. Trees are noticeably affected and are unmarketable that season. Symptoms Needles on lower, interior branches become brown but remain firmly attached in late summer and early fall. Cool moist weather during needle emergence and early shoot growth favors disease development. The result is a needle cast of noble fir and, to a lesser extent, grand fir Christmas trees. It is unknown whether one or more of these fungi are the primary cause or simply infect necrotic needles that have died from some other factor(s). They include Phaeocryptopus nudus, Phyllosticta abietina, and Rhizosphaera pini. however, several other fungi colonize the affected needles but are found less frequently. It is thought that it is due to the fungus Mycosphaerella sp.
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