Susceptibility of Eight to Comandra Blister in Tennessee

B. W. KAUFFMAN, Forest Insect and Disease Specialist, and H. W. APPLEGATE, Assistant State Forester, Tennessee Division of Forestry, Nashville 37220; C. E. CORDELL, Nursery Disease Specialist, Forest Pest Management, SEA, S & PF, USDA Forest Service, Asheville, NC 28803; and E. THOR, Professor of Forestry, University of Tennessee, Knoxville 37901

of seedlings or a sunken canker on large ABSTRACT stems. Aecial fruiting was also frequently KAUFFMAN, B. W., H. W. APPLEGATE, C. E. CORDELL, and E. THOR. 1980. Susceptibility associated with these symptoms. of eight pine species to comandra blister rust in Tennessee. Disease 64:375-377. Five 4-m 2 subplots were established randomly in the first replicate to Field studies in Tennessee compared the relative susceptibilities of eight pine species to natural determine the annual abundance and infection by comandra blister rust (Cronartium comandrae) over an 8-yr period after planting. distribution of false toadflax . Each Pond, shortleaf, and slash were most susceptible. Loblolly and Virginia pines were less subplot contained one pine seedling as susceptible, and eastern white pine, red pine, and Japanese black pine were resistant. Differences in location of comandra rust needle infection were observed among pond, shortleaf, and slash pines. well as false toadflax plants at the time of An apparent minimum 2-yr period was needed for developing rust stem cankers to cause tree establishment. The false toadflax locations mortality after natural direct stem infections through attached needles. All rust stem cankers were stem-mapped on gridded paper detected during the first 5 yr after planting caused mortality the subsequent year on all susceptible during the study examinations each species. Proximity of the alternate host, false toadflax, to infected pines was an apparent spring from 1969 through 1977. requirement, but false toadflax abundance was not correlated with subsequent incidence of rust-caused stem infection and mortality. Loblolly and shortleaf pine plantings should be avoided on sites where false toadflax would be close to the majority of planted pine seedlings. RESULTS The relative susceptibility of the eight species of pines to C. comandrae branch In the South, comandra blister rust Tennessee, false toadflax occurs scattered and stem infections and subsequent rust in Table 1. (Cronartium comandrae Pk.) has been in localized areas on dry sites in the open mortality are summarized found in Alabama, Arkansas, Kentucky, or under a thin overstory. This herbaceous Survival of all eight species averaged 80 of 100 trees after the first year, with no Mississippi, Missouri, and Tennessee perennial is highly intolerant to shade (3,6,9,15,16). Previously, the disease was (15). evidence of comandra rust branch or or associated mortality. reported primarily on ponderosa pine The objectives of our study were 1) to stem infections Pond pine had the best survival (95 trees), (Pinusponderosa)and lodgepole pine (P. determine the relative susceptibility of worst survival (36 contorta)in the West and on jack pine (P. eight species of pines to natural C. and red pine had the trees). banksiana)in the north central states (3). comandrae infection and subsequent Despite the lack of any detectable The fungus also infects Jeffrey pine (P. mortality and 2) to examine the relation aecial fruiting or stem swellings in 1970, jeffrey), knobcone pine (P. attenuata), of these two factors to the abundance and both comandra rust stem infections and pitch pine (P. rigida), red pine (P. proximity of the alternate host. subsequent mortality were observed on resinosa), Scotch pine (P. sylvestris), shortleaf, pond, and slash pines in 1971. Swiss mountain pine (P. mugo), and MATERIALS AND METHODS The initial C. comandrae aecial fruiting Table Mountain pine (P. pungens) (3,12). The following species of pines were was detected in 1972 on all five Susceptibility of red pine is questioned planted in February and March 1969: susceptible species. All stem cankers (10). Artificial inoculation of Austrian loblolly, shortleaf, Virginia, pond, 1973 resulted in pine (P. nigra) with C. comandrae has eastern white (P. strobus), Japanese detected in 1972 and mortality the next year. The only rust- been successful in nursery and greenhouse black (P. thunbergiana),red (P. resinosa), caused mortality on Virginia pine was studies in Minnesota (2). and slash. The eastern white and observed in 1974. Neither C. comandrae Some species of southern pines are Japanese black pine seedlings were 2 yr infection nor mortality was detected on hosts for this obligate fungus parasite. old and the red pine was 3 yr old. any of the eastern white, red, or Japanese Among them, loblolly pine (P. taeda) and Seedlings of the other five species were 1 sprouting after shortleaf pine (P. echinata) are the most yr old. The pines were planted at The black pines. Basal stem on one rust- commonly affected (3,8). In addition, the University of Tennessee's Highland Rim stem mortality was observed killed shortleaf pine, two rust-killed pond rust occurs on naturally infected Virginia Forest near Tullahoma in four replicates pines killed by other pine (P. virginiana), pond pine (P. in an open hardwood stand. Grass and pines, and two pond causes. Multiple C. comandrae branch serotina), spruce pine (P. glabra), and lower vegetation were removed, and the infections were observed on two shortleaf slash pine (P. elliotti) in Tennessee hardwood overstory was injected with a A total of 33 C. comandrae stem (1,4,13). herbicide before planting. Each replicate pines. infections were observed from 1970 The alternate host of the comandra contained 25 seedlings per species. Five this varied significantly rust fungus in eastern North America, plots with five seedlings per plot were through 1974; among years (P = 0.05, chi-square test). false toadflax or comandra (Comandra randomly planted in each replicate at a and 2.4 m The total rust-caused mortality for the has a wide- spacing of 1.8 m within umbellata ssp. umbellata), 8-yr period was 36 pines, representing 7% spread natural range that extends east of between rows. The study site encompassed of the 500 pines of the five susceptible the Great Plains from Canada southward an area slightly less than 0.4 ha. Data were collected anually during the species planted. to upper South Carolina, Georgia, The C. comandrae needle infection Alabama, Mississippi, and Arkansas season of maximum C. comandrae aecial fruiting, which ranged from the last week location differences observed among (11). On the Cumberland Plateau in important in of April to the first week of May, from these species of pines are 1970 through 1974 and in 1977. Rust determining the rate of disease progres- symptoms consisted of either a spindle- sion. Stem needles were the most 00191-2917/80/04037503/$03.00/0 apparent origin of all C. comandrae 01980 American Phytopathological Society shaped swelling on the branches or stem Plant Disease/April 1980 375 infections observed on all species of Consequently, 81% of all observed C. pine overstory along with increasing susceptible pines through 1971. This comandrae infections and 86% of all herbaceous and woody plant competition, trend continued on all slash pine initial observed rust-caused mortality occurred the presence of the alternate host rust infections and 80% of all pond pine in this replicate. Rust-caused infections in decreased through 1977 (23 plants per 4 initial rust infections through 1974. replicates two, three, and four represented m) after yearly population fluctuations. Beginning in 1973, however, needles only 11, 8, and 0% of the total infection, attached to branches were the primary respectively. DISCUSSION source of comandra rust infections on False toadflax populations were Pond and shortleaf pines were the most shortleaf pine. On this species, 57% of all observed and summarized annually on susceptible to C. comandrae; both rust initial rust infections apparently originated five 4-m plots between 1969 and 1977 infections and mortality were highest on through branch needles. (Table 2). The largest population these two species. Similar data were C. umbellata was observed in significant occurred in 1970, with an average of 76 obtained in shortleaf pine plantations on numbers in 2 only the first replicate of plants per 4 m . Primarily as a result of the Ozark and Ouachita National Forests seedlings, encompassing a 24 X 36 m area. increasing shade from the developing in northern Arkansas, where infection ranged from a trace to 68% and mortality ranged from 1 to 40% (16). Table 1. Cronartiumcomandrae branch and stem infections and subsequent rust mortality on pine C. comandrae infections and mortality species in Tennessee on loblolly pine, previously reported as a highly susceptible species (8,15), were Pine species Year surprisingly low. The data in our study, Tree condition 1970 1971 1972 1973 1974 1977 Totals however, are in line with the 7% infection Eastern white level on 3-yr-old field plantings of Living" 89 84 83 81 76 70 70 loblolly pine reported in an earlier study Japanese black (14). In addition, the relatively low rust Living" 69 67 65 64 55 43 43 infection and mortality were comparable Loblolly to the infection (6%) and the mortality Branch infections 0 0 0 1 0 0 1 (2%) previously observed in 30 loblolly Stem infections 0 0 2 0 1 1 3 pine plantations in four Mortality 0 0 0 2 0 0 2 Tennessee Livingb 89 87 87 84 84 84 84 counties on the Cumberland Plateau (5). Pond A relatively low susceptibility of Branch infections 0 0 0 2 1 0 3 Virginia pine to C. comandrae infection Stem infections 3c 1 5 2 1 0 12 and subsequent mortality is also Mortality 0 3 1 5 3 1 13 suggested by the results of our study. Living 95 92 89 81 79 79 79 These results agree with those previously Red reported by Powers (14), where less than Living' 36 30 25 24 19 18 18 1% of Virginia pine seedlings developed Shortleaf natural Branch infections 0 0 1 4 3 0 8 C. comandrae infections in field Stem infections 3c 0 2 1 3 0 9 plots on the Cumberland Plateau. The Mortality 0 3 0 3 1 5 12 lack of comandra rust infections on Livingd 86 80 77 75 73 68 68 Japanese black pine has also been Slash reported (7). Branch infections 0 0 0 0 0 0 0 Infection trends observed on all species Stem infections 5c 1 1 0 0 0 7 of pines showed that only two of nine C. Mortality 0 5 1 1 0 1 8 comandrae branch cankers observed Living 82 72 67 61 59 52 52 through 1973 resulted in tree mortality Virginia the following year, Branch infections 0 0 1 0 0 0 1 whereas five of the Stem infections 0 0 0 1 1 2 3 remaining seven branch cankers formed Mortality 0 0 0 0 1 0 1 stem cankers. Disease symptom expression Livingd 91 91 90 84 81 78 78 apparently did not progress sufficiently Totals to permit detection of rust stem cankers Branch infections 0 0 2 7 4 0 13 during the spring of 1970, so that both Stem infections 11e 2 10 4 6 3 34 stem f cankers and mortality were Mortality 0 11 2 11 5 7 36 observed in 1971. Consequently, an Living 637 603 583 554 526 492 492 apparent minimum 2-yr period is needed aNo infections. for developing rust stem cankers to cause blncludes infected pines. tree mortality after natural direct stem clnfection not detected in late April but assumed present in 1970 because of mortality in 1971. infections dOnly 98 shortleaf and 99 Virginia pines planted. through attached needles. eStem infections varied significantly (P = 0.05) among years (chi-square test). Whenever rust stem cankers were detected during any year from fIncludes 1975, 1976, and 1977 mortality. 1971 through 1974, mortality was detected the subsequent year. This infection and mortality pattern, which accounted for Table 2. Number of Comandra umbellata ssp. 2 umbellata stems on five 4-in plots in Tennessee 96% of the variation in rust-caused mortality (r = 0.98), would most likely be Year evident during the firstS5 yr of the rotation Plot number 1969 1970 1971 1972 197-3 1974 1975 1976 1977 Mean length of the pine plantation but may 1 28 32 50 52 31 8 19 25 38 31 have less correlation thereafter because of 2 37 115 48 40 41 4 26 7 14 37 the larger stem diameters. 3 50 147 41 79 44 4 27 29 47 52 The apparent reduction of long- 4 8 13 7 5 7 3 6 3 1 6 distance spread of C. comandrae 5 23 74 79 64 38 17 16 13 17 39 infection Mean 29 76 45 48 32 7 19 15 23 from the false toadflax in the first replicate to pines in the other three 376 Plant DiseaseNol. 64 No. 4