DANGEROUS INTERNATIONAL FOREST TREE DISEASES HI 



Brown-Spot Needle Blight 



A. F. Verrall 



Forest Service, U.S. Department of Agriculture, 

 New Orleans, Louisiana 



Scirrhia acicola (Dearri.) Siggers is a needle spot and dieback mainly 

 of Pinus palustris before height growth starts. The common spot is 

 straw yellow at first, often with chestnut-brown borders which may 

 become dark purplish in autumn; individual spots are about 3 mm. 

 across but several often coalesce, and as the needles die from the tips, 

 the green tissue between spots shrinks more, resulting in an embossed 

 appearance. Some spots consist of an amber-yellow band with a small 

 brown center. 



Conidial stage is Lecanosticta acicola (Thum.) Syd. Acervuli in- 

 nate-erumpent, at first globose, 50-100/x across, becoming elongate up 

 to 1.5 mm. Conidia mostly 1-3 septate, sickle-shaped, 0.5-4 X 27-32/u, 

 pale brown, discharged through clefts in epidermis in sticky matrix, 

 disseminated mostly by rain splash. 



Ascigerous stage: stromata compact, linear, non-clypeate, innate- 

 erumpent, 1-18 locules mostly in single row, 40-80/a diameter, not dis- 

 tinctly ostiolate; asci aparaphysate, 6-9 X 30-35/x, 8-spored; spores 

 hyaline, 1-septate, oblong-cuneate, 3-4 X 9-16^. Ascigerous locules 

 often develop marginally to acervuli. Conidia produced all year; 

 ascospores mostly in winter and spring. 



Brown spot is one of the major obstacles to the successful regenera- 

 tion of Pinus palustris over wide areas in SE. United States. The 

 disease causes chronic defoliation which either kills seedlings or delays 

 initiation of height growth for many years. This pine is typically very 

 resistant after reaching a height of 75 cm. P. taeda may be heavily 

 attacked at all ages but most dieback occurs in the lower crown late 

 in the growing season and, therefore, is less deleterious. Occasionally 

 the fungus causes serious needle dying on other pines, including P. 

 strobus. 



Intercontinental spread through shipment of seedlings is highly 

 probable, for even with rigid fungicidal spraying some infection occurs 

 in most pine nurseries. Pollen and seed shipments appear safe. 



Range : Common in the coastal States from North Carolina to Texas. 

 Also reported inland as far as Missouri and Ohio. Occasionally 

 in SW. and NW. United States. 

 Hosts: Pinaceae — 



Pinus palustris Mill. 



P. taeda L. 



P. elliottii var. elliottii Little & Dorman 



P. strobus L. 



P. echinata Mill. 



P. glabra Walt. 



P. rigid a Mill. 



P. serotina Michx. 



P. virginiana Mill. 

 Also occurs on following introductions to eastern United States: 



P. attenuata Lemm. 



P. contorta Dougl. 



