Naemacyclus minorNeedlecast of Scots Pine in Massachusetts

Abstract

FREDERICK, R. D., L. ZANG, W. MERRILL, and T. A. TATTAR. 1980. Naemacyclus minor needlecast of Scots pine in Massachusetts. Plant Disease 64: 1034. Needlecast caused by Naemacyclus minor was found in Scots pine Christmas tree plantations in three towns in central and western Massachusetts. This is the first report of this pathogen from New England. In 1932, Darker (2) ascribed a Naemacyclus was associated with needlecast of Pinus spp. in Massachusetts needlecast of Scots pine in Massachusetts. and elsewhere to the fungus Naemacyclus niveus (Pers. ex Fr.) Sacc. Questions arose regarding the morphological variation in and the pathogenicity of this species; some workers considered the fungus a saprobe. Butin's ( I ) separation of the monotypic genus into two species, N. niveus and N. minor Butin, based on minor differences in size of apothecium, asci, and ascospores and major differences in pycnidiospore size and host range, eliminated the confusion over the observed morphological differences. Kistler and Merrill (3) demonstrated that N. minor is a primary parasite causing needlecast of Scots pine (Pinus sylvestris) in Pennsylvania. However, N. n i v e u s , a p p a r e n t l y g r o w i n g a s a saprophyte, also has been collected from trees affected by N. minor needlecast in Pennsy lvan ia (Merr i l l a n d Z a n g , unpublished). The following studies were done to determine which species of Contribution 1193, Department of Plant Pathology the Pennsylvania Agricultural Experiment Station. Approved for publication as Journal Series Paper 5999. 0191-2917/80/11103401/$03.00/0 @ 1980 American Phytopathological Society MATERIALS AND METHODS In November 1979, branches bearing needles with symptoms of Naemacyclus needlecast, a yellowing and casting of the second-year needles, were collected from commercial Scots pine Christmas tree plantations in Alford, Leichester, and Princeton, MA. In all three plantations, approximately 80% of the trees showed symptoms; approximately 50% of the second-year needles on each affected tree were symptomatic a t the time of inspection. The sizes of the apothecia and ascospores on symptomatic 1978 needles were measured. Symptomatic 1978 needles were surface-sterilized with 1% sodium hypochlorite for 1 min, rinsed in distilled water, cut into thirds, plated onto acid malt agar (20 g of malt extract and 15 g or powdered agar per liter of distilled water, acidified with 1.0 ml of concentrated lactic acid per liter after autoclaving), and incubated in diffuse light at 21 C. After 9 days, hyphal tips from colonies resembling those of Naemacyclus spp. were transferred to plates of neomycin and streptomycin agar (15 g of powdered agar per liter of distilled water; 1 g of streptomycin and 0.12 g of neomycin per liter added af ter autoclaving) and incubated at 21 C. After 3 wk of growth, hyphal tip transfers from the ncomycin and streptomycin agar were rlade to plates of malt agar (20 g of mall extract and 15 g of powdered agar per liter of distilled water) and incubated at 21 C until pycnidia developed. RESULTS AND DISCUSSIOP~ The average length of the apothecia on 60 needles from Princeton was 519 p m (range, 292-8 10 pm). The average width of the apothecia was 349 p m (range, 225-540 pm). The average length of 80 ascospores from several apoth1:cia was 78.8 p m (range, 54.0-106.2 pm). The average length of 80 pycnidiospores of each isolate produced in vitrc was as follows: Alford-5.7 p m (range, 4.0-8.8 pm); Leichester-5.5 p m (range, 4.0-7.2 pm); Princeton-7.3 Mm (range, 4.8-9.6 pm). The sizes of the apo thez ia a n d ascospores were within the ranges reported for N. minor (I). Pycnic~iospores were somewhat smaller than reported for N. minor, but the average length fell within the range reported by Elutin (I). Thus the fungus associated with the needlecasts of Scots pine in Massachusetts is N. minor. This is the first conl'irmation of this pathogen in the New England states. LITERATURE CITED 1. B U T I N , H . 1973. M o r p h o l o g ~ s c h e u n d taxonomische Untersuchungen an h aemacyclus niveus (Pers. ex Fr.) Fuck. ex Sacc. und verwandten Arten. Eur. J. For. Pathol. 3:146-163. 2. DARKER, G. D. 1932. The Hypodermataceae of conifers. Contrib. Arnold Arboretum, 1. 131 pp. 3. KISTLER, B. R., and W. MERF ILL. 1978. Etiology, symptomology, epidemiology and control of Naemacyclus needlecast of Scotch pine. Phytopathology 68:267-271.