Arboriculture & Urban Forestry 37(6): November 2011 2009 Experiment Because no crown discoloration was observed in 2008 with Alamo or Arbotect 20-S, tree crowns were only evaluated for discoloration at the time of first inoculation with O. minus (28 days post-treatment); no discoloration was observed. The fungicide treatment main effect and the treatment × time period interaction were highly significant (F = 9.80, DF = 4, 45, P < 0.001 and F = 7.83, DF = 4, 45, P < 0.001, re- spectively), leading to further comparisons among treatments being carried out separately by time period. Trees treated with Alamo produced the smallest lesions at both time periods. At the first time period, untreated trees produced the largest le- sions, followed in order by the 2:1 (Arbotect 20-S:Alamo v/v mixture), the 3:1 mixture, Arbotect 20-S, and Alamo. Only Alamo was significantly different from the untreated trees, and no other difference among treatments was significant (Figure 2). At the second time period, which was more than one year after tree injections, Alamo was again the best treatment and at this date was significantly better than any other treatment (Figure 2). No other treatment differed from untreated trees at the sec- ond time period. This result supports the findings of the 2008 experiment, where the impact of Alamo was still observed in the final sample period, more than two years after treatment. DISCUSSION The objective of this study was to evaluate the effective- ness of systemic fungicides against the bluestain fungus, Ophiostoma minus, in loblolly pine. Alamo was clearly the most effective treatment, and attempts to improve its activity through mixing with Arbotect 20-S were ineffec- tive despite the reduced viscosity of the mixture. The re- sults support the findings of other researchers, who have deployed Alamo against bluestaining fungi [e.g., laurel wilt (Mayfield et al. 2008)], and suggest that this prod- uct has a wide breadth of activity against these fungi. Although the southern pine beetle is thought to be a primary agent of mortality, it is uncertain whether management of the fun- gal associates can assist in tree protection. The relationship of the characteristic blue stain in the sapwood and etiology of bluestain disease in conifers has been a question of much debate (Ayer et al. 1986; Paine et al. 1997; Klepzig et al. 2005; Six and Wing- field 2011). Even when bluestaining fungi do not cause conifer mortality, they have deleterious effects on the remaining wood and may prevent the recovery of incompletely attacked (insecti- cide treated) trees. The control of beetle-associated fungal growth thus remains important regardless of the ultimate cause of tree mortality. This study suggests that fungicides may have a role to play in this type of tree protection and that Alamo is the most effective product of those evaluated. It was the best fungicide in these experiments for prophylactic treatment against O. minus, and the study authors believe evidence is building for the effec- tiveness of this product generally against ophiostomatoid fungi. These studies may be useful to the arborist in the manage- ment of vascular wilt disease in coniferous trees, for examples, 1) that systemic applications may play a role in the protection of susceptible trees, 2) injection of systemic fungicides into the restrictive vascular system (tracheids) of conifers is possible us- ing a pressurized system such as the Tree I.V., 3) the systemic fungicide, Alamo, is effective in limiting ophiostomatoid lesions 291 (as applied, prior to infection), and 4) that activity of the fun- gicide was observed for more than two years, suggesting that the need to reapply may be likewise extended to that interval. Acknowledgments. We thank B. Parpart, J. Parpart, S. Walters, and L. Reed (USDA Forest Service, Southern Research Station, Pineville, Loui- siana, U.S.) for technical assistance in all facets of the study. J. Mahfouz provided O. minus cultures, assisted with inoculations and subsequent data collection, and provided training on related methods. Funding for this study was provided by Arborjet, Inc. and the USDA Forest Service, Southern Research Station, RWU-4552. We thank the Winn Ranger Dis- trict (Kisatchie National Forest), in particular Chad Knight, for assis- tance with site selection and use. We thank Dr. David Cox, Syngenta Crop Protection, LLC,. for his review and comments. Any use of trade, product, or firm names is for descriptive purposes only and does not im- ply endorsement by the United States Government. LITERATURE CITED Alamo Fungicide. Material Safety Data Sheet. Syngenta Crop Protec- tion. Canada, Inc. Ayer, W.A., L.M. Browne, M.-C. Feng, H. Orzanska, and H. Sadeei- Ghomi. 1986. The chemistry of the blue stain fungi. Part 1. Some me- tabolites of Ceratocystis species associated with mountain pine beetle infected lodgepole pine. Canadian Journal of Chemistry 64:904–909. Clarke, S.R., and J.T. Nowak. 2009. Revised. Southern pine beetle. For- est Insect & Disease Leaflet 49. US Department of Agriculture, For- est Service. Pacific Northwest Region (R6). Portland, Oregon. 8 pp. Grosman, D.M., and W.W. Upton. 2006. Efficacy of systemic insecti- cides for protection of loblolly pine against southern pine engraver beetles (Coleoptera: Curculionidae: Scolytinae) and wood borers (Coleoptera: Cerambycidae). Journal of Economic Entomology 99(1):94–101. Grosman, D.M., C.J. Fettig, C.L. Jorgensen, and A.S. Munson. 2010. Effectiveness of two systemic insecticides for protecting western conifers from mortality due to bark beetle attack. West. Journal of Applied Forestry 25(4):181–185. Grosman, D.M., S.R. Clarke, and W.W. Upton. 2009. Efficacy of two systemic insecticides injected into loblolly pine for protection against southern pine bark beetles. Journal of Economic Entomology 102(3):1062–1069. Haugen, L., and M. Stennes. 1999. Fungicide injection to control Dutch elm disease: understanding the options. Plant Diagnostics Quarterly 20(2):29–38. Klepzig, K.D., and B.L. Strom. 2011. Effects of a commercial chitosan for- mulation on bark beetle (Coleoptera: Curculionidae) resistance param- eters in loblolly pine. Journal of Entomological Science 46:124–134. Klepzig, K.D., D.J. Robison, G. Fowler, P.R. Minchin, F.P. Hain, and H.L. Allen. 2005. Effects of mass inoculation on induced oleores- in response in intensively managed loblolly pine. Tree Physiology 25:681–688. Klepzig, K.D., J.C. Moser, F.J. Lombardero, R.W. Hofstetter, and M.P. Ayres. 2001. Symbiosis and competition: complex interactions among beetles, fungi, and mites. Symbiosis 30:83–96. Mayfield, A.E., III, E.L. Barnard, J.A. Smith, S.C. Bernick, J.M. Eick- wort, and T.J. Dreaden. 2008. Effect of propiconazole on laurel wilt disease development in redbay trees and on the pathogen in vitro. Arboriculture & Urban Forestry 34(5):317–324. Paine, T.D., K.F. Raffa, and T.C. Harrington. 1997. Interactions among scolytid bark beetles, their associated fungi, and live host conifers. Annual Review of Entomology 42:179–206. ©2011 International Society of Arboriculture
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