Early instar larvae
Middle instar grub in partially fed sugarcane bits
Pupa (fibrous cocoon removed)
Rearing in sugarcane bits
Rearing adults (split sugarcane bits removed)
Damaged coconut palm cut to show exit hole marks
Damaged coconut palm cut to show various stages of grubs (inset enlarged grubs)
Toppled coconut palm crown due to severe damage
Red Palm Weevil damage resulting in fall of young Date Palm
Coconut Palm with bunches
Date Palm bearing profusely
Dr P S P V Vidyasagar in lab
Palms around the world are ruthlessly attacked and damaged by the Red Palm Weevil. It targets coconut, date, oil and other palms causing great economic loss to the growers. In some countries it not only causes direct losses but also transmits diseases as a vector of dreaded red ring disease in oil palm in latin American countries.
The red weevil is reported to be a native of south Asia but surprisingly no natural enemy of any consequence is noticed in this part. Perhaps that is the reason why the pest has spread to newer regions in the past two decades at a phenomical speed. As the scientific community makes concerted efforts to suppress the pest, evidence is emerging about the occurrence of the pest from newer areas and continents.
On a evolutionary basis, it is safe to say that the red palm weevils are divided in to several species. The ones present in Asia especially India, Sri Lanka, Malaysia etc are categorized as Rhynchophorus ferrugineus Oliv. The species found in Americas is R. palmarum and the one in Africa is R. phoenicious.
Prevention is better than cure. So it is always advantageous to restrict the entry of the weevil stages into the palms. As a prophylactic measure, young palms may be soaked with a pesticide at periodic intervals. This will kill the hidden adults in the palm crowns and also any pest stages present in crevices and damaged tissues.
1. Rhynchophorus ferrugineus Oliv - Asia, Africa, Europe
2. Rhynchophorus palmarum (L) - Mexico, Central and South America
3. Rhynchophorus cruentatus (F) - Florida, the coast of south-eastern USA, South Carolina to Texas
R. ferrugineus is essentially a pest of palms, being recorded on Areca catechu, Arenga pinnata, Cocos nucifera, Borassus flabellifer, Phoenix dactylifera, Phoenix sylvestris, Phoenix canariensis, Elaeis guineensis, Calamus merillii, Caryota maxima, Caryota cumingii, Corypha gebanga, Corypha elata, Livistona decipiens , Metroxylon sagu, Oreodoxa regia, Sabal umbraculifera, Trachycarpus fortune, Washingtonia sp., etc. It can also attack Agave Americana and sugarcane ( Saccharum officinarum).
Most important palms are Coconut palm, Date palm and Oil palm.
Almost the entire damage is caused by the larvae that feed on the inner tissues of host palm near the crown or some part of the trunk region. In coconut the damage is towards the upper portion of trunk but in date palm the damage is more at the base of the trunk. The external symptoms produced by the pest attack include the presence of small bore holes on the stem, oozing out of brown viscous liquid, spit out chewed tissue fibers and longitudinal splitting of leaf bases. Sometimes the trunk becomes hollow with severe damage to the inner tissues. In the final stages the crown gets toppled as a result of severance of crown from main stem.
Coconut palm damage percentage: Generally the extension agencies record the number of infestions by the pest to understan its severity in a given location, region, province etc. This will help in formulation extension programs to suit the local needs.
The infestation may be categorized into three damage stages such as, mild, medium and severe. The palm with mild damage will have small holes and oozing of brown viscous liquid. In the second stage, the palm will show clear indication of damage, with extrusion of chewed up fibers and bad smell emanating from the wounded tissues. The frass mixed with sap forms small lumps and drops to the ground in some young palms. The severely damaged palm may show yellowing of leaf on the side of damage, besides all the above symptoms in a much more exagerated fashion. The damge to stem might be severe and can only be estimated upon proper inspection and cleaning of wounds. The palms in the first two categories of damage can be rescued to a large extent but the revival of the severely affected palms depends on several factors.
Coconut palm monitoring: The palms in the age group of 5-20 years should be regularly surveyed for identifying any infestation. This has to be done atleast once in a month.
Date palm monitoring: In date palm gardens, young palms should be checked thoroughly. Palms with offshoots on the stem should be subjected to more vigorous inspection so as to identify any hidden pest infestation. As the offshoots breakout from the side of the mother’s stem, many crevices are created, facilitating the entry of weevil adults for egg laying and further development. Hence, the growers should employ good methods of survey and surveillance to avoid any fresh infestation.