Conventional and alternative pre-harvest treatments affect the quality of ‘Golden Delicious’ and ‘York’ apple fruit

Abstract

Apple trees cv. ‘Golden Delicious’ and ‘York’ were sprayed from bloom to fruit maturity with different products to evaluate the effect of pre-harvest treatments on fruit quality, including insect/disease damage and physicochemical fruit traits. Apple trees were assigned to five treatments: unsprayed (control), holistic solution (foliar nutrients and probiotics), insecticides, antimicrobials (fungicides and antibiotics), and a combination of antimicrobials + insecticides. The treatments started soon after bloom and were carried out every two weeks until fruit were ready to harvest. Diseases such as sooty blotch (complex of several fungi) and flyspeck (Zygophiala jamaicensis Mason) were the major source of damage on fruits. ‘Golden Delicious’ trees had a higher percentage of undamaged fruit than ‘York’, but all trees had some percentage of damaged fruit. Damage was most severe in the control (unsprayed) and insecticide treatments, intermediate in the holistic treatment, and much lower in the antimicrobial and antimicrobial + insecticide treatments (p < 0.003 for all comparisons). There was also a significant interactive effect (p < .0001) of cultivars and pre-harvest spray treatment on apple fruit mass. For both cultivars there was a strong effect of spray treatment on size, with larger apples produced in the antimicrobial and antimicrobial + insecticide treatments, but these effects were more pronounced in 'York' than in 'Golden Delicious' apples. ‘Golden Delicious’ trees produced 1.4-fold heavier and bigger fruits compared to ‘York’ and ‘Golden Delicious’ fruit were more mature than ‘York’ at harvest. Pre-harvest treatments also affected other quality parameters of apple fruit, such as soluble solids content (SSC) and starch-iodine index. Using partial least squares discriminant analysis (PLS-DA), ‘Golden Delicious’ fruit could be well classified according to the holistic, antimicrobial, and antimicrobial + insecticide treatments. Control and insecticide samples clustered together, indicating similarities between fruit quality. Overall, pre-harvest spray treatment affected the quality of ‘Golden Delicious’ and ‘York’ apples, mainly the fruit mass and disease infection.