Early almond harvest as a strategy for sustainable irrigation, pest and disease management

Abstract

Almonds (Prunus dulcis (Mill.) D. A. Webb) are one of the most economically important agricultural commodities in California. As production in the state continues to increase, growers seek sustainable methods to manage agricultural water use and pests that are affordable and environmentally sustainable. The primary objectives of this research were to test the efficacy of hull split regulated deficit irrigation in combination with early harvest of almonds (Prunus dulcis (Mill.) D. A. Webb) for improved irrigation efficiency and control of navel orangeworm (NOW) (Amyelois transitella (Walker)) and hull rot (HR) (Rhizopus stolonifer (Ehrenb:Fr.) Vuill.; Monilinia fructicola (G. Wint.) Honey). Standard Harvest (SH) timing was compared to Early Harvest (EH) timing at approximately three to four weeks earlier in two California almond orchards using a randomized complete block design at each orchard. Stem water potential (SWP) measurements were used to monitor tree water status and manipulate irrigation to prepare trees for EH treatments. Trees were maintained at -1400 to -1800 kPa SWP for two to three weeks leading up to both EH and SH. There were significantly lower HR strikes in EH treatment trees than in SH treatment trees, and significant reductions in the percentage of kernels infested with NOW when EH was employed. There were no significant kernel yield, marketable yield, or shaker efficacy differences between the two treatments. Although 83.3 and 40.9 mm less water was applied to EH trees than SH trees at the Denair and Woodland sites respectively, the trees from both treatment regimes at both sites returned to the same water status after SH and recovered from the induced moderate water stress by the same date after harvest. With further development of complementary harvest and processing strategies, early harvest of almonds shows promise as a strategy for improved water use efficiency and pest and disease control in almond orchards.