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Investigations of the ash yellows disease: Fluctuations of mycoplasma-like organism populations and effects of antibiotic injection
Abstract
Fifty white ash (Fraxinus americana) in West Springfield, MA, naturally infected with ash yellows (AY) Mycoplasma-like organism (MLO) were observed monthly, from September 1986 to August 1989. The symptoms were witches'-broom (WB), foliar chlorosis (CHL), deliquescent branching (DB), tufting (TF), premature spring bud break (PSB), and premature autumn coloration (PAC). Every August each tree was rated for decline in less vs. more than half the crown. All symptoms except PSB and PAC differed between these two groups. In the $>$1/2 group, incidence of WB, CHL, and TF increased significantly each year, but DB, PSB, and PAC did not. MLO was verified monthly by DAPI staining which was proved to be superior to Dienes' stain in our study. In twigs, both groups showed more MLOs in summer than winter; in roots, conversely. MLO population was more stable in roots than in twigs. Fifteen AY-infected white white ashes were injected twice, in September 1986 and June 1987, with 4% oxytetracycline (OTC) using Mauget trunk injection (average 0.8 g active ingredient (a.i.) / tree). MLO population decreased both in the twigs and the roots for 30 days following OTC injection, then increased to the control level. Fifteen more AY-infected white ashes were injected in June 1987 with 4% OTC Mauget injection at variable dosages (average 0.8, 1.1, 1.6 g a.i. / tree). Higher dosages of OTC decreased the MLO population for approximately two months. OTC therapy may be the most efficient at high rates on trees without decline symptoms, i.e. early in disease progression.
Recommended Citation
Cha, Byeongjin, "Investigations of the ash yellows disease: Fluctuations of mycoplasma-like organism populations and effects of antibiotic injection" (1990). Doctoral Dissertations Available from Proquest. AAI9022670.
https://scholarworks.umass.edu/dissertations/AAI9022670