EFFECTS OF ANTIBIOTIC INJECTION ON ASH YELLOWS-INFECTED WHITE ASH (FRAXINUS AMERICANAL.)

Abstract

Summary Fifteen white ash (Fraxinus americana L.) naturally infected with ash yellows (AY) Mycoplasma-like organism (MLO) were injected twice, in September 1986 and June 1987, with 4 per cent Oxytetracycline (OTC) using Mauget trunk injection (average 1.2 g active ingredient (a.i.)/tree). MLOs were not detected in the twigs or in the roots for 30 days following OTC injection, then increased gradually to the control level. Fifteen more AY-infected white ashes were injected in June 1987 with 4 per cent OTC Mauget injection at variable dosages (averages 1.2, 1.5, 2.4 g a.i./tree). Higher dosages of OTC decreased the MLO population for approximately two months. Similar injections of penicillin and of streptomycin had no effect on MLO populations. OTC therapy may be the most efficient at high rates on trees without decline symptoms, i.e. early in disease progression.