Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. a! p ) Baran Seven Chemicals Fail To Protect Agriculture roest sevice PONderosa Pine From Armillaria researen'siston ~— FROOt Disease in Central Washington PNW-RN-460 Gregory M. Filip and Lewis F. Roth As Abstract Chemicals were applied once to the root collars of small-diameter ponderosa pine (Pinus ponderosa Dougl. ex Laws.) to prevent mortality caused by Armillaria obscura (Pers.) Herink Roll-Hansen (=A. mel/lea sensu lato). After 10 years, none of the 15 treatments appeared to reduce mortality in treated trees vs. untreated trees. Diameter growth of surviv- ing trees averaged 3.0 millimeters per year, and the spread rate of the fungus averaged 0.6 meter per year. Keywords: Root rot, Armillaria, fungus control/prevention, ponderosa pine. Introduction Damage in commercial conifer forests caused by Armillaria is widespread and can be severe in western North America (Wargo and Shaw 1985). Near Glenwood, Washington, root disease in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) stands has been under study for the past 20 years. Research to date has concentrated on epidemiology and damage reduction (Filip and Roth 1977; Roth and others 1977, 1980; Roth and Rolph 1978; Shaw 1980; Shaw and Roth 1976; Shaw and others 1976). These and other studies show that Armillaria infection at the root collar of ponderosa pine, a principal host, results in mortality and that lateral root infections are much less lethal (Adams 1972, Shaw 1980). At least two chemicals, copper sulfate (Reitsma 1932, Thomas and Raphael 1935) and iron sulfate (Gard 1925, Thomas and Raphael 1935), applied as root collar drenches, are effective in protecting trees from Armillaria attack. Also, several fumigants eliminate Armillaria from woody inoculum: these include chloropicrin (Filip and Roth 1977, Godfrey 1936), carbon disulfide (Fawcett 1925, Filip and Roth 1977), and methyl bromide (Filip and Roth 1977, Larue and others 1962). The objective of our study was to test the effective- ness of benomyl, captan, copper sulfate, iron sulfate, copper wire, vorlex, and chloropic- rin in protecting the root collars of living and presumably uninfected ponderosa pine in central Washington from mortality caused by Armillaria. Materials and Methods The study area is near Glenwood, Washington, in a young-growth pine forest. The topog- raphy is flat to rolling, elevation varies from 750 to 1050 meters, and precipitation is 65 to 90 centimeters per year (table 1). Plant communities range from Pinus ponderosa/ Purshia tridentata at the lower elevations to Pinus ponderosa/Pseudotsuga menziesii/ Carex geyeri at the higher elevations (Franklin and Dyrness 1973). Density of understory trees more than 2.5 centimeters in diameter at 1.4 meters above ground (DBH) ranges GREGORY M. FILIP is research plant pathologist, Pacific Northwest BSW FORP aoe Research Station, Forestry and Range Sciences Laboratory, EXPERIMENT STAT La La Grande, OR 97850. LEWIS F. ROTH is professor emeritus, Oregon TION State University, Department of Botany and Plant Pathology, Corvallis, OR 97331. from 2,500 to 5,000 trees per hectare. Site index at 100 years is moderate to good and ranges from 27 to 34 meters. Stands in the study area have been selectively harvested for the past 35 years by the Champion International (formerly St. Regis) Paper Company and the Washington State Department of Natural Resources. A total of 180 ponderosa pine trees from 7 to 15 centimeters DBH were selected at seven locations within the study area on the basis of high exposure to infection by Armillaria. Probability of infection was regulated by distance from apparently advancing margins of Table 1—Site and stand characteristics of 7 locations treated with chemical protectants, Glenwood, Washington Location Plant Trees/ha Side index designation Elevation community >2.5cmDBH _ at 100 years Meters Meters A 760 Pinus ponderosa -4,940 34 Ceanothus velutinus Purshia tridentata B 760 Pinus ponderosa 4,075 29 Purshia tridentata C 990 Pinus ponderosa 3,210 32 Pseudotsuga menziesii Carex geyeri D 850 Pinus ponderosa 2,965 27 Ceanothus velutinus E 790 Pinus ponderosa 3,950 31 Ceanothus velutinus Purshia tridentata IF 990 Pinus ponderosa 2,470 28 Pseudotsuga menziesii Carex geyeri G 850 Pinus ponderosa 3,705 27 Ceanothus velutinus Results and Discussion disease centers (Shaw 1980). All selected trees were within 6.1 meters of the nearest tree showing signs of Armillaria infection (mycelial fans at the root collar). We selected a tree only if the total basal area of infected trees within 6.1 meters of it was between 0.009 and 0.084 square meter. This was done to standardize exposure to inoculum. One of seven chemicals was applied once in August 1973 to each tree selected. Four of the seven chemicals (iron sulfate, copper sulfate, captan, and benomyl) were applied to a small moat (0.3 meter wide) around the root collar of each tree as a 19-liter drench. Nine- teen liters of water were then added to increase percolation. Three concentrations of each material were tested (25, 50, and 100 grams of active ingredient per tree for captan and benomyl; 193, 580, and 963 grams per tree for iron and copper sulfate). Each tree treated with copper wire received 1,135 grams of wire bits (1-2 centimeters long) sprinkled around its base at the root collar zone. Chloropicrin and vorlex (80 percent chlorinated hydrocarbon, 20 percent methy! isothiocyanate) were applied to each appro- priate tree in four filled and capped 132-millimeter polyethylene bottles buried 20 centime- ters at cardinal points around the root collar. (Cooper (1973) demonstrated the slow release of these fumigants from such polyethylene vials.) Control trees received 38 liters of water. Treatments were assigned randomly to the trees. Each location contained some of the treatments, but not all, because of an insufficient number of candidate trees at each location. Tree mortality was monitored yearly, and diameter growth was measured on surviving trees after 10 years. The species of Armillaria causing mortality within the study area was A. obscura (Pers.) Herink Roll-Hansen (=A. mellea sensu lato) or intersterility group | of Anderson and Ullrich (1979); identification was based on pairings of single-spore isolates collected within the study area (Anderson and others 1979). A. obscura is considered to be the most destructive species in western North America (Wargo and Shaw 1985). Ten years after application, none of the 15 treatments appeared to reduce or increase mortality in treated trees as compared to untreated trees (table 2). Differences among treatments were not tested statistically because an insufficient number of trees at all locations precluded performing a balanced, replicated design. Enhancement of Armillaria infection has been reported in inoculated P. ponderosa and P. radiataD. Don seedlings that were treated chemically (Filip 1976, Shaw and others 1980). Except for the first 2 years of the study, when infected trees were probably selected inadvertently, the mortality rate among the 180 trees was fairly constant at about five or six trees per year. The diameter growth rate of trees surviving after 10 years averaged 3.0 millimeters per year (table 3). This rate is much less than the 5.0-millimeters per year diameter growth of dominant trees on each site and probably reflects the overstocked condi- tion of the understory in many locations. Also, the growth rates of infected trees prior to being killed may have been even less, although these rates were not measured. The spread rate of the fungus, measured annually by recording the distance of recently killed trees from apparent infection sources, averaged 0.6 meter per year (table 4). This rate is less than that reported by Shaw and Roth (1976) in the same general area, but they studied the spread of disease over several decades and among much larger trees (70-130 centimeters DBH). Chemical treatments probably did not affect the spread rate in our study because none of the treatments greatly affected tree mortality. The experimental design did not allow statistical testing of this relation. Table 2—Incidence of ponderosa pine mortality caused by Armillaria obscura 10 years after treatment with chemical protectants, Glenwood, Washington Location designation All Treatment A B Cc D E FP G locations Number of dead trees Control 6(14)! 1(3) 2(2) 1(2) 1(1) 0(4) 4(4) 15(30) Benomy|: ; 25g 2(2) 1(2) 1(2) (Gl) OC) ua) Ae) (10) 50 g 1(5) 0(0) 2(2) 0(1) 1(1) 0(0) 1(1) 5(10) 100g 1(2) 0(1) 1(2) 1(3) O(1) 0(0 0(1) 3 Captan: 25g 1(4) 1(1) 0(2) 1(2) 0(0) 0(0) 1(1) 4(10) 50g 0(2) 0(1) 0(0) 2(4) 0(0) 0(2) 1(1) 3(10) 100 g 0(3) 0(0) O(1) 0(1) 1(2) 1(1) 0(2) 2(10) Copper sulfate: 193g 0(0) 2(4) 3(4) 0(2) 0(0) 0(0) 0(0) 5(10) 580 g 1(3) 0(0) 0(0) 2(5) 1(1) 1(1) 0(0) 5(10) 963 g 3(5) 1(2) 0(0) 0(1) 0(0) 0(1) O(1) 4(10) Iron sulfate: | 193 g 0(0) 0(2) 3(3) 1(3) 0(0) 1(2 0(0) 5(10) 580 g 2(4) 0(1) 0(0) 1(1) 1(1) 1(1) 2(2) 7(i0) 963 g 1(4) 0(1) 1(1) 2(2) 0(0) 0(0) 1(2) 5(10) Copper wire 0(2) 0(2) 0(0) 2(3) 0(0) 1(2) 1(1) 4(10) Vorlex 0(3) 0(0) 1(2) 3(4) 0(0) 0(0) 1(1) 5(10) Chloropicrin 1(2) 1(1) 2(2) 1(2) 2(3) 0(0) 0(0) 7(10) Total 19(55) 7(21) 16(23) 18(37) 7(10) 6(15) 14(19) 87(180) iNumber in parentheses is the total number of trees treated. Single applications of chemicals to protect small-diameter pines from lethal infec- tions of A. obscura generally are not effective, but some of the chemicals may pro- tect pines from lethal attack in high-value areas, such as seed orchards, recreation sites, or ornamental plantings, where economics may justify more than one chemical application. More promising in commercial forests is the use of chemicals as eradi- cators of inoculum rather than as protectors. A. obscura can be eliminated from small stumps by injecting the stump with choloropicrin, volvex, vapam, methyl bro- mide, or carbon disulfide (Filip and Roth 1977). Precommercial thinning rather then chemical barriers may be a better method of pro- tecting small-diameter pines from mortality caused by Armillaria. Precommercial thinning on certain sites in Oregon has significantly reduced crop-tree mortality caused by Armillaria (Johnson and Thompson 1975). Density of the understory on many of the Glenwood, Washington, sites is high and growth rates are low. This may predispose understory trees to infection and subsequent mortality, which could be mitigated by precommercial thinning. Current methods of control in the Glenwood area include commercial thinning with stump removal of infected pines (Roth and others 1977) and conversion to Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), which is more tolerant of Armillaria root disease. | Table 3—Mean annual diameter increment of surviving ponderosa pine 10 years after treatment with chemical protectants, Glenwood, Washington Location designation All Treatment A B C D E ie G locations Millimeters per year Control 2.8(8)' 1.9(2) — 4.4(1) — 2.3(4) _ 2.5(15) Benomy!: 25g a 8.8(1) 6.2(1) -— - ~~ _ 7.5(2) 50g 3.2(4) — — 4.6(1) -- _ _ 3.5(5) 100 g 3.0(1) ‘Oly =2:5(9), 8:32)" 2:5(1) — 4.2(1) 4.2(7) Captan: 25g 3.7(3) — 5.5(2) 7(1) — -- — 3.9(6) 50 g 4.9(2) — _- 2.3(1) — 2.1(1) — 3.5(4) 100g 5.1(3) _ 2.8(1) 4.4(1) 3.9(1) 62(1) 1.4(2) 3.9(9) Copper sulfate: 193g — 1.2(2) 1.411) 3.9(3) = — -— 2.5(6) 580 g 1.4(2) 1.6(1) _ 4.9(3) — _ _ 3.2(6) 963 g .7(3) .9(1) -_ 1.4(1) -- 62(1) 2511) 1.9(7) lron sulfate: 193g — 1.4(3) _ 6.7(1) — 2.3(1) — 2.5(5) 580 g 2.5(2) — — _ 2.8(1) — 1.4(1) 2.3(4) 963 g 4.2(3) 1.6(2) = -- — 2.9(1) 3.2(6) Copper wire 3.2(2) 1.4(1) _ 4.4(1) -- 3.5(1) -~ 3.2(5) Vorlex 3.5(2) -- -- 2.5(1) _ _- — 3.2(3) Chloropicrin 1.6(1) — a 3.51); 3.74) = -- 3.0(3) Total 3.0(36) 2.1(14) 3.9(6) 3.7(18) 3.2/4) 2.8/9) 2.3/6) 3.0(93) — = no living trees remaining at that location. ‘Numbers in parentheses are the number of trees measured. Acknowledgments English Equivalents Literature Cited Table 4—Spread rate of Armillaria obscura as determined by annually recording the distance of recently killed ponderosa pine from apparent infection sources, Glenwood, Washington Location designation Year A B Cc D E F G Mean Meters per year 1974 al 1.4 0.9 1975 4 1976 3 USI = 1978 4 1979 if 1980 ‘ — 5 3 3 5 Np —- is S ies a5 S Pe 2 | ak —_ OnnRON®A ON 1981 1982 1983 1984 Mean | lo! olmanvorua! ORRADNOADAOH — = no mortality at that location for that year. The authors thank Len Rolph and Terry Shaw for their assistance and valuable advice in completing this study. 1 meter = 39.37 inches 1 square meter = 10.7639 square feet 1 centimeter = 0.3937 inch 1 millimeter = 0.0394 inch 1 hectare = 2.4710 acres 1 gram = 0.03527 ounce Adams, D.H. The relation of cover to the distribution of Armillaria mellea in a ponde- rosa pine forest. Corvallis, OR: Oregon State University; 1972. 115 p. Ph.D. thesis. Anderson, J.B.; Ullrich, R.C. Biological species of Armillaria mellea in North Amer- ica. Mycologia. 71: 402-414; 1979. Anderson, J.B.; Ullrich, R.C.; Roth, L.F.; Filip, G.M. Genetic identification of clones of Armillaria mellea in coniferous forests in Washington. Phytopathology. 69: 1109- 1111; 1979. Cooper, P.A. The movement of chloropicrin vapor in wood to control decay. Corval- lis, OR: Oregon State University; 1973. 75 p. M.S. thesis. Fawcett, H.S. Bark diseases of citrus trees in California. California Agricultural Experiment Station, Bulletin. 395: 3-61; 1925. Filip, G.M. Chemical applications for control of Armillaria root rot of ponderosa pine. Corvallis, OR: Oregon State University; 1976. 83 p. Ph.D. thesis. Filip, G.M.; Roth, L.F. Stump injections with soil fumigants to eradicate Armillariella mellea from young-growth ponderosa pine killed by root rot. Canadian Journal of Forest Research. 7: 226-231; 1977. Franklin, J.F.; Dyrness, C.T. Natural vegetation of Oregon and Washington. Gen. Tech. Rep. PNW-8. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station; 1973. 417 p. Gard, M.E. Le pourridie du Noyer. Principe du traitement curatif: The root rot of walnuts. The basis of curative treatment. Revue de Botanique Appliquee et d’Agriculture Colo- niale. 5(43): 217-222; 1925. Godfrey, G.H. Control of soil fungi by soil fumigation with cloropicrin. Phytopathology. 25: 246-256; 1936. Johnson, D.W.; Thompson, J.H. Effect of precommercial thinning on ponderosa pine, Pinus ponderosa, infected with Armillaria mellea. Plant Disease Reporter. 59: 308-309; 1975. Larue, I.H.; Paulus, A.O.; Wilbur, W.D. [and others]. Armillaria root rot fungus controlled with methyl bromide soil fumigation. California Agriculture. 16, N8; 1962. 8 p. Reitsma, J. Studien Uber Armillaria mellea. Phytopathologische Zeitschrift. 4: 461-522; 1932. Roth, L.F.; Rolph, L. Marking guides to reduce Armillaria root rot in ponderosa pine are effective. Forest Science. 24: 451-454; 1978. Roth, L.F.; Rolph, L.; Cooley, S. Identifying infected ponderosa pine stumps to reduce costs of controlling Armillaria root rot. Journal of Forestry. 78: 145-151; 1980. Roth, L.F.; Shaw, C.G.., Ill; Rolph, L. Marking ponderosa pine to combine commercial thinning and control of Armillaria root rot. Journal of Forestry. 75: 644-647; 1977. Shaw, C.G., Ill. Characteristics of Armillaria mellea on pine root systems in expanding centers of root rot. Northwest Science. 54: 137-145; 1980. Shaw, C.G., Ill; MacKenzie, M.; Toes, E.H.A. Pentachlorophenol fails to protect seedlings of Pinus radiata from Armillaria root rot. European Journal of Forest Pathology. 10: 344-349; 1980. Shaw, C.G.., Ill; Roth, L.F. Persistence and distribution of a clone of Armillaria mellea in a ponderosa pine forest. Phytopathology. 66: 1210-1213; 1976. Shaw, C.G., Ill; Roth, L.F.; Rolph, L.; Hunt, J. Dynamics of pine and pathogen as they relate to damage in a forest attacked by Armillaria. Plant Disease Reporter. 60: 214- 218; 1976. Thomas, P.H.; Raphael, T.D. Armillaria control in the orchard. Tasmanian Journal of Agriculture. N.S. VI, 1:1-6; 1935. Wargo, P.M.; Shaw, C.G.., Ill. Armillaria root rot: the puzzle is being solved. Plant Disease. 69: 826-832; 1985. U.S. Department of Agriculture Pacific Northwest Research Station 319 SW. Pine Street P.O. Box 3890 Portland, Oregon 97208 Official Business Penalty for Private Use, $300 do NOT detach label July 1987 BULK RATE POSTAGE + FEES PAID USDA-FS PERMIT No. G-4