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THE PINEAPPLE WEEVIL (METAMASIUS RITCHIEI MARSHALL; COLEOPTERA; CURCULIONIDAE)
By MICHELLE SHERWOOD
INTRODUCTION: In 2003, the Entomology Unit, Bodles Research Station, received samples of pineapple fruits and stalk infested /damaged by a beetle larva. After several field visits and literature research, it was determined that the problem was caused by an insect called the pineapple weevil, Metamasius ritchiei Marshall (Coleoptera; Curculioinidae; Calandrinae).
DISTRIBUTION: M. ritchei was first reported in 1916 from Above Rocks (St. Catherine), Jamaica. A survey conducted in 1956/57 determined that the pest was also present in the parishes of St. Andrew and Portland. The survey also determined clearly defined areas of infestation:
The samples submitted in 2003 to Bodles were from Lawrence Tavern (St. Catherine) an area located within the above-defined zone, a few miles from Above Rocks. At least 12 other species within the genus Metamasius, occurs in the neotropical region in countries such as the United States (Florida state), Mexico, Panama, Venezuela, Costa Rica and Honduras.
DESCRIPTION: The eggs are oval, dull, white, and semi-transparent. The larvae are white except the head, which is light brown in colour; legless and grows to a size of 2.5 cm. The adult pineapple weevil is uniform black in colour, without scales or hairs. The length excluding the snout is 19.5-20.5 mm and 7.7-7.5 mm wide. The prothorax and the venter are very shiny. The elytra are broadest at the shoulders and gradually get narrow behind. The coxae have a small tuft of reddish hairs.
Figure 1-3: Metamasius ritchiei Mshl .; 1. Larvae; 2 , Drawing of adult (a. Dorsal view b. Side view c. hind tibia); 3. Adult weevil
DAMAGE SYMPTOMS: In the 1956/57 survey it was reported that the larvae of the pest tunnelled into the fruit –stalk and/or fruit, weakening the stalk and creating a gelatinous ooze at the point of entry or injury at the point of entry of the fruit (Figures 2 & 3). Severely infested fields showed yellowing of the plants. Advanced stalk infestations resulted in breaking of the stalk and falling over of the fruit, as the stalk was unable to bear the weight of the fruit. The fruit was then considered unfit for human consumption.
BIOLOGY AND ECOLOGY: Gowdey (A Government Entomologist) studied the lifecycle of M. ritchiei in 1922. The lifecycle is completed in 12 – 15 weeks (3 – 4 months). The eggs are oviposited singly in shallow excavations made usually in the fruit stalk at the junction of the stalk and fruit of the pineapple. The larvae hatch in eight to ten days and tunnel upward in the rootstock or fruit stalk or in the fruit itself. The larval stage lasts 8 – 10 weeks. The pupa is formed at the extremity of the tunnel lasting 18 – 24 days. The adults are poor fliers and require a great deal of protection from the direct rays of the sun. It prefers a very humid environment as it shows a preference for the recesses of dense vegetation.
Plant Protection Officer, Crop and Plant Protection Unit, Research and Development Division
Fig. 4-6 : Damage caused by larvae of M. ritchiei to pineapple; 4. Exterior of plant stalk; 5 Interior of plant stalk; 6 , Interior of fruit.
In the 1956/57 survey it was observed that infestation was generally found in fields where cultural practices were poor and where the plants were covered with weeds, bush or heavily shaded by overhanging trees. No infestation was found on newly established pineapple plants even when adjoined to heavily infested beds. The pest showed a distinct preference for fields, which were left to produce a ratoon crop and the greater number of times the field had been ratooned, increased the likelihood of it being infested.
One specimen of the weevil was found in the rotted pseudostem of banana in Cavaliers, where it was considered to be only resting. Growers in the Above Rocks area suggested the weevil also attacked arrowroot. This claim was never authenticated after the inspection of many arrowroot samples. Other species of Metamasius have been recorded in other countries as pests of bromeliads. Bromeliad samples in the local infested areas need to be examined as a possible alternative host.
INTEGRATED PEST MANAGEMENT STRATEGIES