The leaf miner (Coelaenomenodera elaeidis) is the major pest of the oil palm. Seasonality of C. elaeidis, its natural enemies and their relationship with temperature, rainfall and relative humidity were observed between January 2009 and December 2010 at the main station of the Nigerian Institute for Oil Palm Research. Leaf miner population estimates were obtained from NIFOR entomology division from 1976-1980. This study analyses temporal patterns in leaf miner abundance, and elucidates general patterns and factors influencing leaf miner abundance. Multiple linear regressions were used to analyse the relationship between abundance of leaf miner, its parasitoids and predators and the following climatic variables: maximum and minimum temperature (˚C), rainfall (mm) and relative humidity (%). Climate variables from the month of pest collection (control variable) or from the month before collection (delayed variable) were used. The abundance of leaf miner and predatory ants peaked in the dry season, while parasitoids were most abundant in the rainy season. Significant correlations (P ≤ 0.05) were found between leaf miner, its natural enemies and both control and delayed weather variables. For all years, maximum temperature was the most dominant for all the leaf miner stages. This indicates that the weather variables at both the month of collection and with a delayed month in relation to collection are critical for pest-weather evaluation and important for leaf miner control. Temperature, rainfall and relative humidity had an effect on the population of C. elaeidis, and this effect is manifested primarily in seasonal fluctuations in oil palm agroecosystems. Weather influenced the seasonal population dynamics of C. elaeidis, facilitating early season build-up on the oil palm host crop. Dry season months with resultant higher temperatures recorded higher population of C. elaeidis.

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The potential of two entomopathogenic fungi Metarhizium anisopliae.and Beauveria bassiana for the control of Coelaemenodera elaeidis were evaluated. The objective of this study was to control C. elaeidis using entomopathogenic fungi as biocontrol agents. The pathogenicity of M. anisopliae and B. bassiana isolates were tested using direct contamination bioassay set up of 2.5 g conidia (2.5 g of Metarhizium 2.5 x 10 10 or 2.5g of Beauveria 10 11 ) transferred to the centre of plastic Petri dishes. Results from M. anisopliae studies indicated that C. elaeidis changed from yellow to brown and darker brown colour. Death of C. elaeidis was observed on the fourth day post incubation with 100% mortality and the control treatment recorded 14% mortality. C. elaeidis were observed with white mycelia growth on the ninth day, the green conidia appeared around the cadavers. Using B. bassiana, ingestion of spores caused infection from the mandible which spread to the thorax. Infection spread beneath the thorax colonizing the abdomen with white mycelia growth. Death was observed on C. elaeidis with 100% mortality on the sixth day post incubation. The larvae and pupae recorded deaths on the eighth and eleventh days post incubations with 100% each. The control treatment recorded mortalities at 21% for larvae and 7% for pupae. The study results indicated that both M. anisopliae and B. bassiana have a high potential as biocontrol agents for the control of C. elaeidis.