Rhynchophorus ferrugineus ( Coleoptera: Dryophthoridae) or commonly known as red palm weevil (RPW) is destrictive insect pest of wide range of palm trees.During August 2010, arborists removed a large dying Canary Island date palm (Phoenix canariensis) from a residence in the city of Laguna Beach, Orange County, California and reported finding adult weevils and weevil larvae with associated larval feeding damage in the top portion of palm trunk.
Muhammad Abdul Rehman
University of Sargodha
The weevil were subsequently identified as Rhynchophorus ferrugineus, the red palm weevil (RPW), by experts at the USDA-ARS Systematic Entomology Laboratory in Maryland. This was the first record of this pest in USA.
Red palm weevil may established rapidly in new areas because it has traveled with its food supply, or there are other ornamental or date palms, nearby that it can infest once larvae finish developing and emerge as a new adults. Adult weevil can fly up to 900m at a time so they are strong fliers and can move up to 7km in 3-5 days. The international trade in live palms is the main source that can allow the pest, probably move as eggs, larvae, or pupae hidden inside the palm to move large distances.
The primary host of Red palm weevil include 24 species of palms in 14 genera, including most of the common land scape palms found in Pakistan.
Red palm weevil is considered to be the most damaging insect pest of palms in the world. Usually attracted by the unhealthy trees, but it can also be often attack on the healthy trees. Larvae of RPW feed within the apical growing point of palms creating extensive damage to palm tissues and weakening the structure of palm trunk.
Palm damaged by RPW may exhibit the following symptoms:
- Tunnels presence on the base of frond or trunk of the plant.
- “gnawing” sounds caused on infested plant by larvae feeding inside.
- Oozing of viscous fluid from tunnels.
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Feeding damage leading to the death of infested plant. The primary host of Red palm weevil include 24 species of palms in 14 genera, including most of the common land scape palms found in Pakistan. Commercial date palm production is impacted in areas where RPW is established, resulting in tree death.
Clean and clear cut, amputate frond, or even a broken leaves emerging from the top of the plant crown. Weevils damage when they enter in palm through crown, and effected the growth of the new leaves, ultimately killing the palm. Sign to view out for the new leaves in the center of the crown that look sparse , lean or weak, or that show signs of heaving been eaten.
The common symptoms of infestation is usually visible only long after the palm has been infested. Holes anywhere on the trunk, near the crown or bases. Emergence holes and tunnels produced y the adult weevils after removal for inspection will be especially visible in fronds. It can also be detect detritus produced by feeding larvae, and the feeding of the larvae, presence of larvae and pupal cause of weevils. Unpleasant of rotting vegetation and brown viscous liquid oozing out from wound on the trunk surface. Frond discoloration and when infestation is advanced:
Red palm weevil can be present on the palm all the year, although the adult weevil are more active during summer season. Females will prefer to lay eggs on palms that are diseased or in bad condition. All stages of red palm weevil (egg, larva, pupa and adult) are spent their time inside the palm itself and the life cycle cannot be completed elsewhere. Female laid about 300 eggs in different holes and injuries on the palm. Eggs hatch in 3-5 days into grubs which bore into the tree interior moving by peristaltic muscular contraction of the body and feeding on the soft succulent tissues, and discard all fibrous material of the plant. Larval period varies from 1to 3 months.
The grubs pupate in an elongate oval, cylindrical cocoon made out of fibrous strands. At the end of the pupation period adult weevils emerge. Thus the life cycle is about 4 month and continuous throughout the year. Weevils become dormant during winter month and spread during summer or warm month. Weevils will established their homes when there is sufficient live plant material on a palm, feed and lay their eggs on it. Once they have exhausted the food source, the adult will disappear to find new plant for attack.
Noise of crunching, literally! From within the trunk as the larvae eat their way into the tree’s life force.
Control and management:
Suppression of red palm weevil infestation can be attempted in several ways. The main method which can be used mostly is the application of systematic insecticides. Insecticide is usually applied through a funnel 5cm above the infested area of the trunk. Red palm weevil can be monitored using pitfall traps, and alternative form of control use sanitation and mass trapping with traps. A genetic control method in which Male Sterile Technique (MST) can also be used to control red palm weevil. Through this method X-rays and Gama rays radiation have been used to induce the sterility of male. However these methods are under experimental stage. The agriculture department for biosecurity division is essentially needed confinement procedures by establishing demarcated infested areas. It also have need to regulate import requirements and condition for moment of palm.
In Pakistan resistance was assessed against the formulated commonly used chemical insecticides profenophos(500g/liter, 500EC), imidacloprid(700g/liter, 70EC), chlorpyrifos(400g/liter, 40EC), cypermethrin(100g/liter,10EC), deltamethrin(25g/liter, 10EC), spinosad(240g/liter, 24EC), lambda-cyhalothrin(50g/liter, 5EC) and a fumigant phosphine tablets. Resistance of elevated level were record for deltamethrin, phosphine and cypermethrin use in Pakistan after a long history of insecticide. The result suggest that lambda-cyhalothrin and spinosad exhibit unique mode of action and given batter environmental figure. A changed pattern of both insecticides can be used sensibly recommended dose rates and frequencies.
Potential threat of RPW to palm industry
RPW considered as rear and local insect in natural and uncultivated areas. However, with commercialization of palm it has caused drastic increase and rapid spread of RPW in southern Pakistan. As such, this weevil consider to be a one of the destructive pest that will bluster the survival of palm, which represent the backbone of Pakistan commodity. Pakistan has more than 75,000 Hectors of date palm, which provide a stable source of income to many smallholders. Therefore, urgent action is required to avoid significant economic yield losses before it is too late.
For the sustainability of the red palm weevil management, comprehensive and effective control measures must be considered seriously due to its impact on major palm all over the world. Early detection and monitoring of the pest management is essential in order to implement of an effective pest management. More study can also be required on a new methods of control pest.