Invasive Species Compendium

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Abstract

The effect of Oecophylla longinoda (Latr.) (Hym., Formicidae) on coconut palm productivity with respect to Pseudotheraptus wayi Brown (Hem., Coreidae) damage in Zanzibar.

Abstract

A total of 1025 coconut palms of the East African Tall variety in 41 small-holding plots were examined twice in a survey of Pseudotheraptus wayi damage conducted during July 1992-January 1993 on the island of Unguja, Zanzibar. Oecophylla longinoda, the most important predator of P. wayi, was present on 34 and 37% of the palms in the 1st and 2nd surveys, respectively. Strong colonies occupied 12% of the palms during both surveys. The remaining palms were either weakly occupied or the predator was found only once. The average annual yield of palms with strong and stable O. longinoda colonies was 57 nuts, while palms without O. longinoda had an average yield of 41 nuts. Palms with varying degrees of O. longinoda colonization showed an increasing annual yield with a corresponding increase of O. longinoda activity. Intense O. longinoda colonization resulted in a significant reduction of female flower formation as well as less damage due to P. wayi. The number of 7- to 8-month-old nuts increased significantly with each increase in O. longinoda activity on palms. The average number of nuts per inflorescence ranged from about 2.7 nuts on palms without O. longinoda to 4.1 nuts on palms with stable colonies. The formation of female flowers per inflorescence, the level of P. wayi damage and the retention of nuts varied seasonally, among the plots, individual palms and also within inflorescences on the same palm. Palms with strong ant colonies displayed less fluctuation in flower production and nut set which resulted in a more stable harvest.