Subtropical Fruit Crops Research & Education
University of California
Subtropical Fruit Crops Research & Education

Posts Tagged: Date Palm

Palm Weevil Threat to Palm Trees

Date growers in the California deserts have many insects to worry about such as carob moth, hibiscus mealybug, and giant palm borer. Now the industry is under threat from another potential pest, the highly damaging and invasive South American palm weevil (SAPW) (Rhynchophorus palmarum). It was first identified by county and state agriculture officials in 2011 in San Ysidro in San Diego. They made the discovery while looking for a closely related palm weevil, R. vulneratus (originally mis-identified as the notorious red palm weevil, R. ferrugineus), which was found in Laguna Beach and declared eradicated in Jan. 2015.SAPW has been reported on at least 35 plant species in 12 families and is especially economically important on plantation crops such as oil and ornamental palms of which date palm, Phoenix dactylifera, is a recorded host (CABI 2016; Dean 1979; Esser and Meredith 1987). SAPW has killed hundreds of Canary Island date palms (P. canariensis) in Tijuana and parts of San Diego County. These large urban infestations pose a significant risk to the multi-million dollar date palm industries (edible fruit and ornamentals) in the Coachella Valley. Losses of ornamental Canary Island date palms in San Diego County, are probably significant and likely now reaching millions of dollars in killed palms, reduced aesthetics, and increase removal costs.

SAPW has a long rostrum (this is the beetle's snout) and is large often up to 1 ½ inches to 2 inches in length (CDFA 2018). SAPW is now California's biggest weevil species! Inside the palm crown, weevil larvae feed on the meristematic tissue and it is this feeding that kills the palm crown which results in palm death. Larvae pupate inside 3-inch cocoons made of palm fibers. The pupal stage typically lasts two to three weeks. Adult weevils emerge from these protective cocoons, mate, and they are capable of flying significant distances, perhaps as far as 15 miles in a single day, to find new palm hosts. Female weevils use their snout to chew holes in the apical regions of the palm and they lay eggs in these holes. Larvae that hatch from eggs burrow into the palm crown and feed turning the meristem tissue in a fermenting “mash”. Feeding wounds that result in fermenting damage in association with aggregation pheromone released by male weevils create a highly attractive airborne cocktail of odors that weevils fly too. Adult weevils can live for at least 40 days, often longer (CDFA, 2018).

A single infected palm can result in the production of hundreds of weevils and detection of weevil infested palms at the early stages of attack can be difficult to identify because larvae live inside their host trees. The first obvious symptom of attack is a crown that is starting to collapse. Unless palms are treated within systemic insecticides at the early stages of attack, infested palms will ultimately die in as little as 2-3 months once visual symptoms become apparent.

In addition to direct physical damage SAPW inflict via feeding, it is a primary vector of the nematode that causes red ring disease (RRD), a fatal wilt disease of palms. Fortunately, RRD has not yet been detected in SAPWs or palms attacked in San Diego (Hoddle et. al. 2016). Removal of infected trees is necessary not only to remove breeding weevil populations from the environment, but also to minimize risk of harm to people, pets, and property from crown and frond drop.


More information on the SAPW invasion and to report suspect palms please visit this website:

Posted on Monday, March 26, 2018 at 7:27 AM

2017 Date Field Day: A Success!

The University of California Cooperative Extension (UCCE), UC Riverside, United States Department of Agriculture/Agriculture Research Service (USDA/ARS), and the California Date Commission hosted a Date Field Day on February 15, 2017 at the UC Riverside Coachella Valley Agricultural Research Station. It was a full house that day, with approximately 55 Growers, farm managers, and other date stakeholders. The field day included a field research plot tour, lunch, and Continuing Education hours where available for attendees.


Speakers included Tom Perring, UCR Professor of Entomology, who spoke about his Pink Hibiscus Mealybug biocontrol research. Pink Hibiscus mealybug is a new threat to the date industry. This insect has a host range of 200+ trees species. The first findings where on backyard tree species and has been spreading to agriculture commodities and has just recently has become an issue in dates. Perring is currently in the early stages of rearing a parasitoid that may be able to help reduce the mealybugs population.

Robert Krueger, Citrus and date researcher Riverside USDA/ARS spoke about nitrogen assessment of date palms. He discussed diagnostic sampling implications, which suggest that there are differences in concentrations of various elements that occur in different portions of the leaf, and at different aged leaves can show different results, and also different seasons may also effect results. Based on the research it is suggested that the best sampling strategy is near khalal stage from middle pinnae of intermediate aged leaves during the summer.


Tony Fortier, from Phoenix Agrotech spoke about tissue culture methods in date palms. Date palm tissue culture is a rapid clonal propagation (micropropagation) method, where a small piece (explant) of the desired mother plant is initiated under sterile conditions into an in vitro environment, such as a test tube or culture vessel. Under tissue culture conditions, cells of the explant undergo rapid multiplication, ultimately producing many young date palm plantlets, which are genetically identical to the desired mother palm. This method is currently being used in the industry.

Peggy Mauk, UCCE-UCR Subtropical Horticulture Specialist spoke about establishment of date palms: Tissue Culture vs Off-shoots.

Locally, field plantings are threatened by pests and diseases. Globally, field plantings are threatened by climatic changes, human expansion, and political unrest. Therefore, maintaining and securing genetic diversity for improved cultivation and pest & disease resistance is crucial. MaryLou Polek, from the USDA/ARS spoke about the Role of the USDA Germplasm Repository and the importance of the collection.


 Sonia Rios, UCCE Riverside/San Diego Counties Subtropical Horticulture Farm Advisor spoke about pest issues in date palm, more specifically about weevils . Date palms flourish in high summer temperatures and low humidity which creates a perfect breeding ground and living conditions for pest, especially for the Red palm weevil (Rhynchophorus ferrugineus) (RPW) and South American palm weevil (Rhynchophorus palmarum) (SAPW). The RPW is considered most destructive arthropod pest of palms world-wide. SAPW causes similar damage on smaller scale. Both larvae's can cause economic damage as they feed on palm near apical growing point causing damage, which weakness the tree, and eventually causes death. The SAPW has been eradicated, however the RPW has been slowly showing up in date species in California, threatening the date industry. (Weevil Photos: Mark Hoddle)

The California date industry is worth ~$68 million (NASS, 2015). In 2015, 43,600 tons of dates where harvested. Coachella Valley produces about 95% of the dates consumed in the US. Date palms flourish in high summer temperatures and low humidity climates, which permits their production to certain growing regions. There are many threats to this economically important commodity and the University of California Cooperative Extension and other agencies are committed to assure the date industry thrives locally and globally.  The planning committee looks forward to next year's event.



Posted on Wednesday, July 5, 2017 at 11:26 PM

Date Palm Field Day

Date Palms were planted in the Coachella Valley of California, which is approximately two hours east of Los Angeles in the early 1890s. And now, plantings cover over 6,500 plus acres. These acres produce over 40 million pounds of our four primary varieties, which are the Deglet-Noor, the Medjool, the Barhi and the Zahidi.Date palms need plenty of ground water to drink, but high heat and arid weather to produce fruit. Therefore, date palms grow best in hot and arid climates.

Come learn about our date industry in California at the 2017 Date Palm Field Day

Time: 8:00 A.M – 3:00 P.M

Location: Coachella Valley Agricultural Research Station 86501 72nd Ave, Thermal, CA 92274


Registration link coming soon

(Online registration available on site day of for walk-ins – payment by Card only)



8:00   Registration

8:20   Welcome – Sonia Rios, CE Advisor

8:30   Tom Perring, UCR - Pink Hibiscus Mealybug biocontrol

9:00   Robert Krueger, USDA/ARS - Nitrogen assessment of date palms  

9:30    Tony Fortier, Phoenix Agrotech - Tissue Culture date palms

10:00     Break

10:15   Peggy Mauk, UCR/CE - Establishment of date palms-Tissue Culture vs Off-shoots

10:45   MaryLou Polek, USDA/ARS -  Role of the USDA Germplasm Repository

11:15    TBD

11:45     Lunch

(Included in registration)

1:30    Field tours

If you have any questions contact: Sonia Rios, UC Farm advisor

951.683.6491 Ext. 224



Posted on Wednesday, February 8, 2017 at 11:55 PM
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