# 2003 Kluwer Academic Publishers. Printed in the Netherlands. Distribution patterns of coconut mite, Aceria guerreronis, and its predator Neoseiulus aff. paspalivorus in coconut palms L.C.P. FERNANDO*, N.S. ARATCHIGE and T.S.G. PEIRIS Coconut Research Institute, Lunuwila, Sri Lanka; *Author for correspondence (e-mail: rescri@sri. lanka.net; phone: þ94 31 55300; fax: þ94 31 57391) Accepted in revised form 8 May 2003 Key words: Aceria guerreronis, Coconut, Distribution pattern, Eriophyidae, Neoseiulus aff. paspali- vorus, Phytoseiidae, Predator–prey dynamics, Sampling Abstract. Distribution patterns and numerical variability of the coconut mite Aceria guerreronis Keifer (Acari: Eriophyidae) and its predator Neoseiulus aff. paspalivorus DeLeon (Phytoseiidae) on the nuts of 3- to 7-month-old bunches of coconut palms were studied at two sites in Sri Lanka. At the two sites, coconut mites were present on 88 and 75% of the nuts but no more than three-quarters of those nuts showed damage symptoms. N. aff. paspalivorus was found more on mature nuts than on immature nuts. Spatial and temporal distribution of coconut mites and predatory mites differed significantly. The mean number of coconut mites per nut increased until 5-month-old bunches and declined thereafter. The densities of predatory mites followed a similar trend but peaked 1 month later. Variability in the numbers of mites among palms and bunches of the same age was great, but was relatively low on 6-month-old bunches. The results indicate that assessment of infestation levels by damage symptoms alone is not reliable. Sampling of coconut and=or predatory mite numbers could be improved by using several nuts of 6-month-old bunches. The effect of predatory mites on coconut mites over time suggests that N. aff. paspalivorus could be a prospective biological control agent of A. guerreronis. Introduction At present, effective control of the coconut mite, Aceria guerreronis Keifer, which is a serious pest of coconut in the Americas, the Caribbean and Africa, is mainly dependant on repeated spraying of highly toxic acaricides=insecticides at short intervals (Herna ´ndez 1977; Julia and Mariau 1979). The possibilities of producing and using the entomopathogenic fungus, Hirsutella thompsonii Fisher are being explored (Lampedro and Luis Rosas 1989; Cabrera 1995). However, screening of less toxic chemicals and exploring alternative control methods, particularly bio- logical control, have to be expedited since A. guerreronis has now invaded India (Sathiamma et al. 1998) and Sri Lanka, which are major coconut-growing countries of south-east Asia. In Sri Lanka the predatory mite Neoseiulus aff. paspalivorus DeLeon is prevalent on infested nuts. This predator has been observed feeding on A. guerreronis and could be a candidate for biological control (Mariau 1977; Howard et al. 1990). Aceria guerreronis colonizes beneath the perianth (tepals) of coconuts and feeds on the meristematic tissue. Coconut mites are present on nuts from the time of Experimental and Applied Acarology 71–78, 2003. 31: