TITLE:
Entire Whitening of Apple Trees to Increase Chill Units in Regions of Warm Temperatures during the Fall-Winter Seasons
AUTHORS:
Alejandro Zermeño-González, J. A. Gil-Marín, H. Ramírez-Rodríguez, A. I. Melendres-Alvarez, M. Cadena-Zapata
KEYWORDS:
Malus domestica Borkh, Chill Units, Whitening, Calcium Hydroxide, Budbreak
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.13 No.8,
August
15,
2022
ABSTRACT: Different studies have shown
that global warming and climate change have increased
the planet’s temperature in different locations. For the apple-growing farmers, this may have a negative impact on the accumulations of chill units
when the air temperature during the fall-winter season increases. When the
entire trees are covered with a reflective material, the wood temperature may
decrease. Therefore, the objective of this study was to evaluate the effect of
whitening (with calcium hydroxide) the entire apple trees (Malus domestica Borkh) after defoliation, on the
branches and trunks’ internal temperature (under the bark), the accumulation of
chill units (CU), its effects on fruit yield and quality and the relation with
the use of thidiazuron (TDZ) (inducer of budbreak). The study was conducted
during the fall-winter seasons of 2019-2020 and 2020-2021. The results of this
study showed that at the hours of the highest incidence of solar radiation, the
internal temperature of the whitened trunks and leaves decreases up to 9°C and 6°C respectively. The accumulated CU during the time of the
study, of the whitened branches were up to 81% higher than the ones recorded on
the branches with no whitening; while the CU was lost at the hours of highest
solar radiation (due to a high temperature) were up to 37.2% smaller. Entire
tree whitening increased up to 26% of the yield per tree compared to the
application of TDZ. No statistical difference in fruit quality was observed
between whitened trees and those with no whitening but with the application of thidiazuron.