Larch Needle Blight

(Hypodermella laricis Tub.)

Larch Needle Cast

(Meria laricis Vuill.)

From: Field Guide to Diseases and Insect Pests of Idaho and Montana Forests, USDA Forest Service Northern Region, Publication Number R1-89-54

Hosts. – Western larch.

Distribution. – Range of host in Idaho and Montana.

Damage. – Both kill infected needles. Growth loss can result from severe infections particularly if successive years of severe infections occur. Seedlings can be killed by severe infections. Spur shoots and, occasionally, succulent new shoots can be killed by Hypodermella laricis.

Identification. – Larch needle cast and needle blight frequently occur together because they require similar conditions for infection. Severity of infections vary greatly from year to year in response to weather conditions. Severity also varies among trees within stands. Infection is usually heaviest low in the crown. Needle cast causes infected needles to be shed within a few weeks of infection. Needle blight kills infected needles quickly and causes the dead needles to remain attached to the spur shoots for 1 to 3 years.

Hypodermella infects young needles early in the spring. The infected needles turn red-brown and droop (fig. 116) within 2 weeks of infection. All or most of needles on a spur are usually infected. Black, oval fruit bodies form on infected needles in late fall and early the following spring.

Meria begins infecting needles in early spring and continues to re-infect throughout the summer if rainy weather continues. Infected needles have discolored spots or bands which are yellow at first, becoming red-brown (fig. 117). Within a month of infection the needles drop to the ground. Minute cushions of colorless spores are produced on needles on the ground. These cushions, which emerge through stomata, are difficult to see without use of special stains.

Similar damages. – Larch casebearer causes defoliation of larch trees which appears superficially like that caused by needle cast or needle blight. Needles attacked by larch casebearer are hollow, shriveled, and kinked (fig. 118). Larch sawfly damage is similar to larch needle cast, but sawfly removes chunks of needles (fig. 119). Shoots fed upon by western budworms look similar to those killed by Hypodermella. Feeding by budworms results in partial severing of the shoot. Frost causes damage to shoots and young needles which may be confused with Hypodermella blight. Frost damage tends to be heaviest in the upper crowns of trees.

	Image Unavailable
Figure 118 - Larch Casebearer hollows needles causing them to droop. Case of feeding casebearer can be seen near the tip of a needle (center).	Figure 119 - Larch Sawfly removes large chunks from needles. The needles may turn yellow or red.

Link to Larch Needle Blight Images in Forestry Images

Link to Larch Needle Cast Images in Forestry Images

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.

Funk, A. 1985. Foliar fungi of western trees. Canadian Forestry Service, Pacific Forest Research Centre BC-X-265, 159 p.

Hepting, G. E. 1971. Diseases of forest and shade trees of the United States. USDA For. Serv. Ag. Hndbk. No. 386, 658 p.

Leaphart, C. D. and R. E. Denton. 1961. Needle discolorations of western larch. USDA For. Serv., For. Pest Leaflet 61, 7 p.

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