Dynamics of the Scale and Its Natural Enemies in a Citrus Grove at Ceiba, Cuba

Abstract

Aim: Research was conducted to study the population dynamics of a citrus scale, and its parasites in “Empresa de Citricos de Ceiba”, Havana Province, Cuba. Orange trees, Glover’s scale Lepidosaphes gloverii (coccidae, homoptera), and four of its natural enemies including three fungi and a parasitic wasp, were studied in their distributions in space and time, and their interactions, in order to understand why this scale is not a serious pest in Cuba. Methodology: The study consists of observations made bi-weekly on the site during an entire year. Various statistical analyses including Taylor regression and new probabilistic methods that were developed for this study were used to explore the mechanisms of natural regulation of the pest. Major findings: The results of the analysis showed that the scale population was kept in check by seasonally varying recruitment and by mortality that was density dependent through gradual parasitization by several species with distinct spatial preferences and some overlapping. The findings also showed that the first natural enemy to settle on the scale did so independently of the number of scales on the leaf; but ones this happens there was contagion within the scales on the leaf. Conclusion: The study demonstrates that the pest can be regulated within an ecological context of community dynamics. A general theoretical result based on loop analysis demonstrates that using pesticides to control agricultural pests where they co-exist with their natural enemies would actually have counterproductive results, in fact increasing the pest.