- Author: Saoimanu Sope
More than 20,000 palms in the region have been killed by South American palm weevil
The swaying palm trees that line San Diego's streets might not be swaying much longer due to a pest that is infecting many of these iconic trees and making its way across Southern California.
The South American palm weevil (SAPW), also referred to as the American palm weevil and black palm weevil, was first detected in San Diego County in 2011, with breeding populations found in a Canary Island date palm in San Ysidro in 2015. According to industry experts, more than 20,000 palms in the region have been killed by SAPW thus far.
While SAPW can attack a variety of palm tree species, Canary Island date palms (Phoenix canariensis) are by far their most preferred host. SAPW adults lay their eggs in the crown of palm trees and then larvae hatch and voraciously consume the growing tissue of the palm. If left unchecked, this pest can kill mature palms in a matter of months.
SAPW has affected neighborhoods and cities throughout the greater San Diego area, creating a need for more residents to be aware of this concern and report infected palms. Though infestation has not been confirmed, SAPW adults have been reported in the Coachella Valley – about 120 miles northeast of San Diego.
‘Super-dispersers' from San Diego can fly long distances
The California Department of Food and Agriculture has trapped weevils in the Coachella Valley and recent posts on iNaturalist, a social network for community members to map and share observations of biodiversity across the globe, indicate that adult weevils are flying into areas where edible dates are grown.
These reports interest researchers like Mark Hoddle, University of California Cooperative Extension based at UC Riverside, because the Coachella Valley, the major production area for edible dates nationwide, is far from any known infested palm trees.
How did the weevils get there? “It may be super-dispersers from San Diego,” said Hoddle. “They are on a death mission when they fly long distances – find food or die trying!”
While conducting an experiment to assess SAPW's flight capability, Hoddle and his team learned that the beetle could fly non-stop for up to five hours, with some variation between males and females. “In some cases, they will fly until they die,” Hoddle said.
Currently, Hoddle is managing an ongoing urban palm surveillance effort of 521 palm trees in and around Bonita in San Diego County, which are assessed every six months. More than 70% of these palms have been killed by SAPW over a 6.5-year period.
Although Canary Island date palms are highly preferred by SAPW, the weevils can complete their entire life cycle in sugarcane as well. For palm species that are not currently preferred by the pest, there is still a chance that they can become more preferred over time as SAPW works its way through all available Canary Island date palms in the region.
Taking action to protect your palms
There are steps that one can take to protect palm trees. Traps can be used to both monitor weevils and reduce the number of adults flying around. There are two types of traps that Hoddle has evaluated for weevil captures: the bucket trap and the Picusan trap. Both use a fermenting bait – prepared with dates, baker's yeast and water – that is placed in a glass jar with a perforated lid, in addition to a commercially available aggregation pheromone that will attract male and female weevils.
Of the two trap types, Hoddle prefers Picusan traps because they catch about six times as many weevils as bucket traps – retaining more than 95% of the weevils that are attracted to them. Bucket traps, on the other hand, retain only about 30% of weevils.
Hoddle emphasizes that trap placement is key. The Picusan trap is designed to be placed on the ground, whereas the bucket trap is typically hung from a tree branch, fence or post. Furthermore, the traps should be placed at least 500 yards away from the potential host palms and avoid direct sunlight. Shaded or partially shaded areas are best to avoid diminishing the trap's potency.
Another strategy is to prune palm trees when SAPW flight activity is low (December through March) to minimize attracting flying adult weevils to freshly pruned palms.
Finally, the best way to protect your tree is to apply insecticides. These chemicals will kill adult weevils that attempt to start infestations. While contact insecticides can deter and kill adults when applied to the crown of the palm, systemic insecticides are usually more effective and can be applied as soil and crown drenches, trunk sprays, or soil and trunk injections. Systemic insecticides move inside the palm and concentrate in the palm heart, the growing area at the top of the palm where weevils feed. Once this growing area is damaged by feeding weevil larvae, palms die.
“Just know that if you are planning to protect palms with insecticides, you are in it for life,” saidHoddle, emphasizing that there is no “one and done” approach to saving palms affected bySAPW. “Don't start if you can't commit.
Aesthetics aren't the only motivation to prevent palm infection and death caused by SAPW. Palm crowns that are highly damaged by larval feeding can detach from the top of the trunk and fall to the ground, putting people and property at risk. Dead fronds drop from dying palms and the large spines at the base of the fronds are a significant hazard to people and pets.
Seek expert support for tree concerns and removal
Removing dead palms is an expensive and time-consuming process. Removal can cost between $2,400 to $4,000 per palm, with cost varying based on location. For example, if a palm is in an area that requires the use of a crane, semitruck or helicopter to safely access, remove and dispose of the dead palm, tree removal can cost up to $15,000.
Once a palm is infested with SAPW, it likely cannot be saved unless it is aggressively treated with insecticides at an early stage of the infestation. If you are certain that a tree is infected by SAPW, it is highly recommended that you work with a tree care company or arborist to manage the weevils that might be present in the palm and to promptly and responsibly dispose of dead palms so that spread of weevils into new areas is minimized.
To confirm visual signs of palm trees that have been affected by SAPW, visit Hoddle's site for more information and to report infested palms: https://cisr.ucr.edu/invasive-species/palmarum-survey.
To read this story in Spanish, visit: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=58381
/h3>- Author: Jeannette E. Warnert
South American palm weevils that have made their way north from Mexico are having a destructive impact on palm trees in the San Diego region, reported Abbie Alford on CBS News 8 TV in San Diego.
UC Cooperative Extension specialist Mark Hoddle, the director of the Center for Invasive Species Research at UC Riverside, toured the reporter through the hard-hit Sweetwater Reserve in Bonita, where 10 percent of the palms die every three months.
“We are going to see hundreds, thousands of Canary Island Date Palms die over the next couple of years,” he said.
The weevils use their protruding noses to drill holes in the palm, where females lay their eggs.
San Diego County Agriculture, Weights and Measurements said it plans to remove 50 infested Canary Island Palms from the Sweetwater Regional Park and is educating arborists about the invasive pest.
A spokesperson for the City of San Diego said it is working with UC Cooperative Extension.
- Author: Sonia Rios
The South American palm weevil has successfully invaded and established in San Diego County where it has killed hundreds of Canary Islands date palms. The weevil is spreading quickly and will likely pose a significant threat to date and ornamental palm producers in the Coachella Valley.
Free Event
Date: March 12, 2018
Location: Coachella Water District, 51501 Tyler St, Coachella, CA 92236
CE and ISA Credits Available
Agenda:
8:00am: Don Hodel, UCCE LA County, will give an overview of palm biology, diseases, and nutrient deficiencies that can be confused with palm weevil damage
8:45am: Tom Perring, UC Riverside, will cover date palm pests
9:30am: Mark Hoddle, UC Riverside, will provide updates on the palm weevil invasion in San Diego County
10:15am: BREAK – Sponsored by the California Date Commission
10:45am: Mike Palat, West Coast Arborists, will review issues that need consideration when removing palm trees killed by palm weevils
11:00am: Ricardo Aguilar, Aguilar Plant Care, will discuss potential chemical control options for palm weevils in infested areas
11:15am: Agenor Mafra-Neto, ISCATech, will discuss new technologies that are commercially
available for controlling palm weevils 12:00pm: Meeting Adjourns
Register for the Meeting Here: http://ucanr.edu/survey/survey.cfm?surveynumber=22821
- Author: Sonia Rios
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.
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.
Peggy Mauk, UCCE-UCR Subtropical Horticulture Specialist spoke about establishment of date palms: Tissue Culture vs Off-shoots.
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.
- Author: Jeannette E. Warnert
One of Los Angeles' quintessential icons - palm trees - are being threatened by an invasive pest from overseas - the South American palm weevil. KQED Science produced a clever overview on the life and times of this devastating pest, punctuating it with a surprise ending that features UC Cooperative Extension specialist Mark Hoddle.
The story outlines the pest's life cycle, which starts when a female lays its eggs in the crown of a palm. They hatch and larvae eat the plant from the inside out, eventually killing the palm. The larvae pupate, complete metamorphosis, then fly off to find another palm to attack.
Hoddle conducted an experiment to determine how far the weevils can fly. He glued the pest on a sort of insect treadmill and let it fly in circles. He found that they can travel up to 15 miles a day, enough to easily hopscotch from palm to palm on their own and spread widely.
The biocontrol scientist demonstrates one way to get rid of South American palm weevils. If you're not squeamish you can view the video on the KQED website.