What is in this article?:
- Weevils threaten Western palm nursery, date industries
- South American palm weevil
- Date production
- Two palm tree weevils found in California threaten the economic vitality of Western nursery stock producers and date growers.
- The red palm weevil is considered the worst palm tree pest in the world.
- The insects could jeopardize California’s $51 million date industry.
South American palm weevil
A South American palm weevil was found May 11, in San Ysidro, a community located in southern San Diego just miles from the Mexican border. This was the first find in the U.S. Several additional SAPWs were found close by in July, says San Diego County Agricultural Commissioner Lisa Leondis.
“The South American palm weevil is a bad pest of palms,” Leondis said. “You can look at a 30-foot palm tree and have no idea the pest is inside. The pest really doesn’t come out much until the tree dies and the top falls off.”
The SAPW is a major pest of oil and coconut palms which can result in tree death. Palm hosts include the date, Canary Island date, coconut, African oil, sago, and Washingtonia fan palms.
Adult insects are completely black sometimes with a velvety-appearance. Adults are 1.5 to 2 inches in length and live for about 40 days.
Female SAPWs deposit eggs into bored holes near palm leaf bases or damaged areas. The holes are sealed with a brown waxy secretion. An average of 245 eggs is laid over the insect’s lifetime with egg hatch in about three days. Like the RPW, larvae damage the tree by feeding on palm tissue in the crown - destroying the apical growth area.
The SAPW is a vector for the red ring nematode, Bursaphelenchus cocophilus; the causal agent of red ring disease of coconut. Tree death can occur five months after inoculation. None of the SAPW captured in San Diego County carried the nematode, Leondis says.
One of the difficulties with this pest is trapping so close to the Mexico border.
“We really don’t have the ability to go full circle around the pest and trap for it,” Leondis said. “We can only trap on the California side of the border.”
CDFA has 315 SAPW traps in San Diego County - 290 in San Ysidro and 25 in Vista. Two traps are placed in neighboring Imperial County.
The nursery plant industry is very disturbed by the weevil findings. In San Diego County, ornamental trees and shrubs, including palm trees, are a $300 million business annually. Most San Diego County nurseries grow palm trees.
An APHIS-SAPW quarantine in San Diego County is inevitable, according to Jim Bethke, University of California Cooperative Extension nursery and floriculture farm adviser in San Diego County. Bethke believes a quarantine would significantly hinder the movement of palms from the quarantined areas.
“The quarantine would likely require nursery growers to hold all palms in the nursery in the quarantine area for at least a year before the plants could be sold,” Bethke said. “During that time pesticide treatments would be required on the palms.”
There is also talk of requiring nursery producers to build screened structures to house palm stock for protection from the pest.
“Screening structures would be extremely expensive for nursery palm producers. The vast majority of them would not be able to afford it,” Bethke said. “Many producers would either stop growing palms or go out of business. That would more or less move palm production industry out of San Diego County.”
Bethke believes agricultural research can provide effective control measures for both weevils. Finding answers would require time and funding. Yet Bethke says dollars for agricultural research across California are limited. Today, dollars are only available for the most “serious” pests.
“The Asian citrus psyllid came along several years ago in California and the dollars to fight the diaprepes root weevil just disappeared,” Bethke said. “If we don’t have the funding to fight the palm weevils, we could battle the pests for a very long time.”