Sodium hydrosulfide as a potential orchard treatment for increasing the yield of avocado (Persea americana Mill.) cv. ‘Hass’

The avocado ( Persea americana Mill.) cultivar ‘Hass’, which dominates global production, is susceptible to winter frost and spring-summer heatwaves. The latter can intensify immature fruit abscission (‘June drop’). Hydrogen sulfide (H 2 S) is an endogenous signaling molecule known to prime plants against multiple abiotic stresses and inhibit organ abscission. Our prior studies demonstrated the beneficial effects of priming ‘Hass’ trees with the H 2 S donor sodium hydrosulfide (NaHS) against cold stress. Based on these, the current study evaluated the impact of combined winter and summer NaHS applications on commercial ‘Hass’ fruit yield. A 3-year field trial was conducted using 80 ‘Hass’ trees [40 control (CR) and 40 NaHS-treated trees], with spray treatments applied three times in winter and three times in early summer each year. NaHS-treated trees had higher mean yields than CR trees in each of the three study years, with the largest differences in year 2. Over the three years, the cumulative yield of NaHS-treated trees was 36% higher by weight and 48% higher by fruit number, although these differences were not statistically significant in all analyses. Spatial assessment of individual tree yields and the alternate bearing index revealed that alternate bearing was asynchronous across the orchard plot, suggesting that the higher yield of NaHS-treated trees was independent of the trees’ baseline physiological bearing state. The established anti-abscission properties of H 2 S combined with the temporal overlap of summer NaHS applications with the natural fruit drop period suggest that exogenous H 2 S may mitigate premature avocado fruitlet abscission, a hypothesis that remains to be tested directly. Pending the development of suitable agricultural formulations and confirmation in larger replicated field trials, orchard NaHS application presents a promising agronomic strategy that may enhance climate resilience, reduce pre-harvest crop loss and improve commercial avocado yields.