THE EFFECT OF PROHEXADIONE CALCIUM, SAR INDUCERS AND CALCIUM ON THE CONTROL OF SHOOT BLIGHT CAUSED BY ERWINIA AMYLOVORA ON APPLE

The efficacy of the plant growth regulator prohexadione calcium (PC), the systemic acquired resistance inducers Harpin and Actigard, and calcium carbonate (Vigor-Cal) were evaluated in an experimental Idared apple orchard.
Shoots were inoculated with Erwinia amylovora strain Ea273 by bisecting the two youngest leaves with scissors dipped in inoculum.
The average shoot length on PC-treated Idared trees (29.6 cm) was significantly less than on untreated Idared trees (49.7 cm). The severity of fire blight was reduced significantly on shoots inoculated 13 and 20 days after treatments with 250 mg/L PC, compared with untreated, inoculated Idared trees.
Vigor-Cal, Actigard and Harpin treatments caused numerical but not statistically significant reductions in disease compared with the untreated control.
Treatment of Idared shoots with PC prior to inoculation resulted in significantly less disease than on inoculated untreated Idared shoots.
Application of PC during the early phase of shoot growth offers a novel approach in managing shoot blight phase of fire blight on apple.

VIII International Workshop on Fire Blight

M.T. Momol, J.D. Ugine, J.L. Norelli, H.S. Aldwinckle

Fire blight, growth regulator, Apogee, Actigard, Harpin, Vigor-Cal

https://doi.org/10.17660/ActaHortic.1999.489.104