2018 ASHS Annual Conference

The United States date industry is small and specialized, requiring specific climatic conditions found only in a limited area in California and Arizona. While the industry has benefitted from low pest and disease pressure that is supported by Federal and State phytosanitary regulations, some pests and diseases have recently been reported from California or have become more prominent in other areas and could inadvertently be introduced to California or the date production area. These are outlined here. Two species of palm weevil (Rhyncophorus spp), which are highly destructive of date palms and other Arecaceae, have recently been reported from California. One, R vulneratus, has been eradicated, whereas the other, R palmarum, remains established approximately 120 miles from the date production area. Palm weevils are destructive on their own but also vector the nematode-associated red-ring disease. The red palm mite, Raoiella indica, has not yet been reported from the date production area but is present in other parts of the United States, Mexico, and the Caribbean Basin. The Giant Palm Borer, Dinapate wrighti, is present in the date production area but is not a problem in healthy, well-maintained orchards; however, periods of stress can cause outbreaks. Fungi are the predominant pathogens of date palms, the most important being caused by Fusarium spp. Bayoud, caused by F oxysporum f sp albidensis, is the most devastating disease of date palms world-wide but is confined to North Africa. F oxysporum f sp canariensis is endemic in coastal California but has not become established in the date production area. Recently a different form, F oxysporum f sp palmarum, has been reported from Florida. Both of these forms can kill date palms. Diseases of date palms associated with Candidatus Phytoplasma spp have been reported from the Middle East, Florida, and Texas, but are not known to occur in California. C P asteris is associated with the Al-Wijam disease in Saudi Arabia, whereas C P cynodontis is the causal agent of white-tip dieback and slow decline in Sudan. Lethal yellows (LY), caused by C P palmae, is a devastating disease of coconut and Phoenix spp are also susceptible. This phytoplasma has been confined to the Caribbean Basin, but a different subgroup of the LY phytoplasma is associated with Phoenix Palm Decline, reported in Texas and Florida. Additional uncharacterized phytoplasmas have been associated with declining palms in Florida and Mexico.