Relationship of Weather Factors to Russet Incidence in ‘Comice’ and ‘Bosc’ Pear Fruit

• Published in: Acta horticulturae no. 1094; pp. 533 - 538
• Main Authors: Sugar, D, Villardel, P, Asin, L
• Format: Journal Article
• Language: English
• Published: International Society for Horticultural Science 01-01-2015
• Subjects: copper hydroxide; correlation; equations; flowering; heat sums; pears; relative humidity; temperature
• ISSN: 0567-7572; 2406-6168
• DOI: 10.17660/ActaHortic.2015.1094.71

Fruit russet incidence can be an important pear quality factor. Data on russet incidence on untreated ‘Comice’ and ‘Bosc’ pear fruit were collected for 13 and 10 years, respectively. Russet in ‘Comice’ was quantified as the percentage of fruit with >6% of the fruit surface covered in russet, and in ‘Bosc’ as the percentage of fruit with >97% russet. Russet incidence at harvest was correlated with records of various weather factors for the multi-year series. Beginning at each date from 21 days before full bloom until 50 days after full bloom, an 11-day moving window was calculated for each weather factor. Coefficients of correlation between weather factors and fruit russet at harvest were then plotted against dates relative to full bloom, and trends based on fifth-order polynomial equations were observed. High negative correlations with fruit russet were observed for temperature-related parameters (maximum and mean daily temperature, mean growing degree days base 10°C, intra-day temperature change). High positive correlations were observed with relative humidity (mean RH, accumulated hours with RH >80%). Peak correlation coefficient values for temperature and humidity factors typically occurred at 15-18 days after full bloom. Copper hydroxide applied to ‘Bosc’ pears at petal-fall enhanced russet and efficacy correlated negatively with temperature and positively with humidity.