Control of fire blight (Erwinia amylovora) with trunk injection of the maximum seasonally allowed doses of SAR inducers and antibiotics in apple trees
S. G. AĆIMOVIĆ (1), Q. Zeng (1), G. C. McGhee (1), J. C. Wise (1), G. W. Sundin (1). (1) Michigan State University, East Lansing, MI, U.S.A.
Trunk injection is a valuable alternative for delivering protective materials which could increase sustainability of tree agriculture by target-precise pest control with no negative effects of pesticides on the environment. Due to a systemic mode of exposure, a significant control of fire blight (<i>Erwinia amylovora</i>) should be achieved through trunk injection of Systemic Acquired Resistance (SAR) inducers. After 1-2 injections of 4 candidate and known resistance inducers and 2 antibiotics, using 4 replicates per treatment, inoculated Gala apple trees were rated for blossom and shoot blight, and Kit Jonathan trees for shoot blight. Similarly to streptomycin with blossom and shoot blight incidences of 17.1 and 4%, candidate inducer potassium salts of phosphorous acid (PhosphoJet) provided significant fire blight control with incidences of 20.4 and 6.5% compared to water injected control (46.1 and 22.3%). Imidacloprid (Imajet) was ineffective with incidences of 40.1 and 18.3%. Two doses of SAR inducer acibenzolar-S-methyl with incidences of 26.9 and 20.3%, and 27.7 and 18.5%, significantly reduced only blossom blight. Inducer prohexadione-calcium did not control shoot blight implying no translocation of the active ingredient. Oxytetracycline (ArborBiotic) significantly controlled shoot blight on Kit Jonathan with time severities of 4.7-14.2% compared to water injected control (30.1-68.6%). The results show that trunk injection could be used for apple disease control.
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