Symptoms and Mechanism of damage
Normally, the Red Palm Weevil prefers to infest palms wounded or below the age of 20 years, where the stem of the young palm is soft, juicy and easily penetrated eggs are laid by adult weevils. The hatching larvae grow rapidly. During their development they tunnel into the terminal bud or trunk of the tree, often leading directly to its death. When a palm is severely infested, the stem or crown sometimes breaks off the tree. The weevils are destructive pests to palms. The larvae are responsible for damaging the palm, and once they have gained access, the death of the palm generally ensues. The larva normally never comes to the surface, since it begins its life inside the palm. Therefore, neither the damage nor the larva can be seen. However, the trunk of the palm can be infested in any parts, including the crown.
The damage caused by a few larvae of the weevil is astonishing. Even one larva may cause considerable damage, and, sometimes the death of the palm. It is difficult to assess the actual loss caused by this pest, but undoubtedly it affects the production of date palms. The crown wilts first, and lower leaves will follow, due to damage to vascular tissue.
Early symptoms of attack are distinctive but hard to see: egg laying notches; cocoons inserted into the base of the palms; an eccentric growing crown; holes at the base of cut palms; symptoms resembling those caused by lack of water such as wilting, desiccation and necrosis of the foliage; tunnelling within the stems and trunk. Larvae and adults destroy the interior of the palm tree, often without the plant showing signs of deterioration unless damage is severe. Hollowing out of the trunk reduces its mechanical resistance, making the plant susceptible to collapse and a danger to the public. In most cases, attack on Phoenix and other palms leads to the death of trees whatever their size. Visual examination allows detection of symptoms but cannot determine if there are larvae and adults present inside the trunk. Pheromone traps, acoustic detection or infrared systems can be used to detect this pest.
Major symptoms such as crown loss or leaf wilt are usually only visible long after the palm has become infested. By the time these symptoms are observed, the damage is usually sufficient to kill the tree. Sounds of the larvae burrowing and chewing can be heard by placing one's ear to the trunk of the palm, and some inspectors use electronic listening devices to detect early infestations.
Preferably young trees were attacked by R. ferrugineus. Killed or weakened palms lead to a remarkable reduction of yield. Cases are reported where whole plantations had to be cut down due to palm weevil infestation. Additionally fruit from infested trees are often of lower quality. Numerous farmers were ruined.
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