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Adult Rhynchophorus palmarum have a black, hard cuticle and they measure about 4–5 cm in length and are approximately 1.4 cm wide. The head is small and round with a characteristic long, ventrally curved rostrum (snout). Adults show sexual dimorphism; males have a conspicuous batch of hairs on the rostrum. The larvae eat and grow within the trees. They are tan with dark brown mouth parts and like other beetle larvae they have no eyes or legs.
Host Plant: Palms of all kinds including Coconut Palms, Date trees, Fruit trees and sugarcane. It has been reported on 35 different hosts from 12 families.
The weevil damages palm trees by direct feeding of the larvae on fruits, stems, buds, and leaves, but also by transmitting the nematode, Bursaphelenchus cocophilus, which can cause red-ring disease in coconut and oil palms. The palm weevils can be born with the nematode in their system, and if any un-contaminated beetles consume diseased tree tissue they are instantly contaminated. Those conditions make this parasite-host system a very serious concern. The weevil can also directly damage crops like sugarcane boring through the tissues of the plant as a larva Rhynchophorus palmarum preferentially attacks weakened or diseased trees but is also capable of attacking healthy trees.
For more information on the nematode Bursaphelenchus cocophilus click here.
A single female of American palm weevil may lay up to 693 eggs under laboratory-controlled conditions, which then hatch in 3-5 days. Larvae of the pest feed exclusively on live vegetative tissues. Larval period completes in 7-8 weeks and prepupal stage lasts for 4-17 days, during this time each larva make a cocoon using plant fibers. The pupal stage lasts for 1-3 weeks. Adult males usually live for 6-8 weeks while adult females live for 5-7 weeks. Adults are usually active at day time. Studies on the population dynamics of this weevil species in Central and South America showed that maximum population occurs during the dry season.
Was first identified in California in 2011. In June of 2012, the Texas AgriLife Extension center and the federal agency APHIS detected the weevil in Alamo, Texas. It was thought to be brought in on an imported palm tree or an ornamental plant.
Central and South America
U.S. Habitat: Palm hosts include: date, Canary Island date, coconut, and African oil palm, sago and Washingtonia fan palms. The weevil has also been recorded feeding on sugar cane. Some adults have been found to feed such fruits as avocado, citrus, guava, mango and papaya; however, the feeding damage is not considered economically significant.
U.S. Present: CA and TX
Trapping the insects can help manage populations but unfortunately, once the weevil is noticed it is too late for the palm tree, the damage has been done. There is no cure or treatment for trees infested with Rhynchophorus palmarum. Endrin can be used as an insecticide to control palm weevil populations, but it is very expensive. Preventative spraying of insecticides on palm trees may reduce weevil population but again it can be very costly for the commercial producers. However, it is the best option so far. Since Rhynchophorus palmarum, is an eminent economical threat APHIS is trying to figure out better and more cost efficient methods to prevent this invasive beetle from decimating the palm/palm oil industry in the United States.
Esser, R. and J. Meredith. 1987. Red ring nematode. Nematology Circular of Florida Department of Agriculture No. 141. Gainesville, FL.
Griffith, R. 1987. Red ring disease of coconut palm. Plant Disease 71:193-196.
Wattanapongsiri A 1966. A Revision of the Genera Rhynchophorus and Dynamis. Department of Agricultural Science, Bangkok (TH).
Wilson M. 1963. Investigations into the development of the palm weevil, Rhynchophorus palmarum. Tropical Agriculture Trinidad 40:185–196.