Freeze Protection in European Pear 2008 Kitren Glozer Department of Plant Sciences, UC Davis Rachel Elkins UCCE, Lake & Mendocino Counties

Flower buds and cold hardiness  Cold hardiness is reduced by –low chill accumulation –cycling warm and cold periods in dormant season –Delayed entry into dormancy –poor nutritional status  Buds ‘at risk’ have poor vascular connections, lower sink strength, low nutrient status and PGR production

4/6 4/7 3/26 Dates of Treatment = tight cluster & 10-20% bloom Killer Freeze Post Petal Fall

Cropload rated May 15, after final fruit drop. Application dateRating ProGibb + Promalin + BlightBanApril 62.0 a ProGibb + PromalinApril 61.4 ab BioForgeMarch ab ProGibb + Promalin+ BlightBan 2xApril 6 & 70.8 b ProGibb + PromalinMarch b ProGibb + Promalin 2XApril 6 & 70.6 b ProGibb + DithaneMarch b ProGibb + Promalin + BlightBan, before freezeMarch b Untreated control0.4 b BlightBanMarch b Whole tree treatments, mistblower, 100 gpa, Breakthru penetrant with all but BioForge

Most promising results after April 20 freeze ProGibb (GA 3 ) + Promalin (GA 4+7 ) with early bloom ProGibb + early bloom BioForge (2% N from urea, 3% soluble potash K 2 O) – only timing tested tight cluster ProGibb + tight cluster Most of crop was lost to late freeze Return bloom and yields from 2008 treatments will be evaluated in 2009 Trial will be repeated in 2009

Acknowledgements Our appreciation to our grower-cooperator and to the California Pear Advisory Board for ongoing support