ISHS Acta Horticulturae 338: VI International Workshop on Fireblight
EFFICACY OF PHOSETYL-ALUMINUM AND COPPER FOR CONTROL OF FIRE BLIGHT ON BLOSSOMS AND SHOOTS OF APPLE |
| Authors: | G.G. CLARKE, K.D. HICKEY, J.W. TRAVIS |
| Abstract:
Efficacy of phosetyl-aluminum (Aliette 80W) and a copper micronutrient for protecting blossoms or shoots against fire blight infection were evaluated in replicated apple orchard experiments in 1989–92. One, two, or three dilute applications of Aliette 600–1200 mg ai/L to open blossoms of 'Rome Beauty' failed to provide protection against blossom blight when blossoms were inoculated with Erwinia amylovora. Inoculations were made by placing 50 ul of a 1 X 108 suspension of Erwinia amylovora directly into the nectary or by lightly swabbing open blossoms with the bacterial suspension. All Aliette treatments, however, provided a significant reduction in the number of naturally occurring fire blighted blossom clusters in 1991 under highly favorable conditions for infection. The range in number of strikes per tree was 114 to 129 compared to 252 on the nontreated checks. No differences were evident under less favorable conditions in 1992 when infections per tree were 2.0 or less. The length of blighted area on shoots treated in 1991 with three applications of Aliette 1200 mg ai/L was 44% of that on nontreated trees. This effect on symptom expression was not significantly different from the check on trees treated with two applications at 600 mg ai/L. The efficacy of one to four foliar applications of a copper micronutrient (Sorba-Spray Cu 4LC) was evaluated on mature 'York Imperial' trees for prevention of shoot blight infection and suppression of shoot blighting after inoculation. Sorba-Spray Cu 62 mg ai/L in one, three, or four applications significantly increased the copper content of shoots, but failed to reduce natural shoot infection or shoot blighting in 1989. One, two, or three applications at 31 mg ai/L in 1990 provided significant reduction in the proportion of shoots blighted compared to the nontreated check. The same treatments in 1991 failed to provide suppression of shoot blighting. | |
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