Short communicationSpur behavior in Almond trees (Prunus dulcis [Mill.] DAWebb): effects of flowers, fruit, and “June drop” on leaf area, leaf nitrogen, spur survival and return bloom

- The competition for nitrogen between fruit and leaves at the spur level occurs during the whole season.
- Fruiting spurs had 50% less leaf area than non-fruiting spurs because they have smaller and less leaves.
- Defruited spurs significantly improved their survival and return bloom probabilities while compared to fruiting spurs.
- Defruited spurs were as likely to survive, but less likely to bloom than non-fruiting spurs.

Effects of flowering, fruiting, and fruit drop on leaf area, leaf nitrogen, probability of spur survival and return bloom were studied in an 11 year-old highly productive almond orchard. Six different spur categories (spurs with no fruit, spurs with flowers removed at full bloom, spurs with fruit removed at 14 days after full bloom (DAFB), spurs with fruit removed at 28 DAFB, spurs with one fruit, spurs with two fruits) were labeled on a total of forty-eight trees, variety Nonpareil. Spurs were tracked from winter 2011 to spring 2012. Spur survival and spur return bloom data were collected by visually inspecting each labeled spur in 2012. Results showed that the competition for nitrogen between fruit and leaves at the spur level occurs during the whole season. Fruiting spurs had 50% less leaf area than non-fruiting spurs because they had smaller and less leaves. Spurs whose fruit was removed early in the season reached similar survival probabilities to spurs that had no fruit throughout the season. However, the return bloom probabilities were lower on spurs whose fruit was removed than in non-fruiting spurs. Two fruiting spurs had the lowest chance to either survive or return bloom.