Response of secondary bloom of 'Bartlett' pear (Pyrus communis L.) to pruning

Type V secondary bloom of pear (Pyrus communis L.) is associated with pruni ng and is frequently infected by fire blight (Southwick et al., 2000). The goal of this research was to determine which pruning practices would most l ikely be associated with subsequent Type V secondary bloom. Pruning date, s hoot age, type of pruning cut and shoot orientation were varied and effect on Type V secondary bloom assessed. In both 1998 and 1999, dormant pruning was more likely to result in Type Vs than summer pruning or pruning one mon th after harvest. Pruning one week after harvest in 1998 was as likely to l ead to Type Vs as dormant pruning, but was less likely in 1999. The likelih ood that Type Vs would occur was lowest from 49 to 89 d from full bloom (DF B) and at 175 DFB in 1998. The lowest likelihood of Type Vs in 1999 was fou nd on shoots pruned at 83 or 185 DFB. The likelihood for Type Vs rose with increasing shoot age from one to four years, but there was no difference be tween three- and four-year old shoots. In 1998, stub cuts (severe heading) were more likely to have Type Vs than head cuts when pruning two year old s hoots, but not for one year old shoots. In 1999, type of pruning cut had an inconsistent effect on the likelihood for Type Vs and was not the same for each shoot age. NAA applied to summer pruned shoots completely prevented T ype Vs from occurring and almost completely stopped Type Vs when applied to dormant pruning cuts. Summer pruning from 50 to 90 DFB or pruning one mont h after harvest and the application of NAA to pruning wounds may be strateg ies for reducing the occurrence of Type V secondary bloom.