Investigating Lemon Fruit Drop (LFD) in the Desert Region

The Desert Region of California accounts for over one-fourth of the state bearing acreage of lemon. Recently, excessive preharvest fruit drop of lemon has been reported by several growers in the Desert Region of California, in addition to lemon growing areas in Arizona, primarily affecting Limoneira 8A, Eureka, and Foothill Lisbon on Macrophylla and Volkameriana rootstocks. Excessive lemon fruit drop is concerning for economic reasons, especially when abnormally high rates of drop are occurring in these orchards just prior to harvest. Fruit drop can be caused by several abiotic factors including drought, fluctuating temperatures, mineral deficiency, under or over irrigation, and heavy pruning, but can also be caused by biotic factors including fungal pathogens such as Alternaria alternata and Colletotrichum acutatum. At present, it is unclear if LFD observed in these desert regions is due to abiotic or biotic factors. This study will determine the cause of the LFD in these regions and determine which management practice(s) are appropriate for alleviating LFD in these regions.