Influence of Chemical Growth Regulation on the Host Susceptibility of Pear Trees for Fire Blight

Suppression of Fireblight in Apple Shoots by Prohexadione-calcium following Experimental and Natural Inoculation

“…Choice of number, rate, and timing of applications may be determined as much by pomological and label considerations as by the ideal choice for effect on fireblight management, but considerations for several uses may be quite compatible. Deckers and Daemen (1993) expressed concern that some plant growth regulators could increase fireblight risk on pear by stimulating secondary bloom production. However prohexadione-Ca's effect on secondary bloom of apples appears to be minimal (Byers and Miller, unpublished data).…”

“…In spite of long-term recognition that tree vigor is an important element in fireblight susceptibility (Van der Zwet and Keil, 1979), few reports have addressed the possibility that plant growth inhibitors could reduce susceptibility or suppress infection. Two reports discuss the potential effects of daminozide (Lombard et al, 1982) and other plant growth regulators (Deckers and Daemen, 1993) on shoot growth, secondary bloom and fireblight risk in pear (Pyrus communis L.). We are not aware of published reports with experimental data that confirm a positive or negative effect of plant growth regulators on fireblight development.…”