Field trapping of the American palm weevil (APW),Rhynchophorus palmarum, showed that the combination of caged male APWs and palm stem was much more attractive to APWs of both sexes than palm stem alone. Caged female APWs did not enhance the attractiveness of the palm. Caged APWs without palm stem were not attractive. Virgin laboratory-bred males were highly attractive to APWs of both sexes in a two-choice pitfall olfactometer, whereas virgin laboratory-bred females were not. Adsorbenttrapped volatiles from virgin laboratory-bred males reproduced the effect of living males, giving evidence for a male-produced aggregation pheromone in this species. Wild-mated APWs of both sexes were as responsive to the aggregation pheromone as virgin laboratory-bred APWs. This is the first record of chemical communication in this species. These results have prompted investigations into the chemical identification of the aggregation pheromone.

No abstract

The leaf miner Coelaenomenodera lameensis Berti & Mariau (Coleoptera: Chrysomelidae: Hispinae) is the most serious pest of oil palm in West Africa. A study of mortality factors was carried out at 19 sites located in seven plantations of 3000 -7000 ha, over a 2 -4-year period in the early 1980s throughout the forest zone of Cô te d'Ivoire, West Africa. All life history stages of C. lameensis were found to be attacked by natural enemies. Fluctuations in numbers of egg parasitoids were related to climatic factors and host population dynamics and parasitism rates varied substantially among sites. High egg mortality in C. lameensis, related to parasitism, was directly linked to climatic factors, mainly relative humidity. Fluctuations in egg mortality not linked to parasitism were similar among plantations. There was also a negative correlation between beetle fecundity and egg mortality; climatic conditions favourable to an increase in fecundity also disfavoured egg mortality. This can be a major cause of population increase of larval C. lameensis. Different species of larval and pupal parasitoids and predators were observed. In addition, viruses, isolated from dead larvae in galleries, killed 55 -60% of the larvae, probably playing an important role in limiting populations. The destruction of mines by several species of ants also eliminated about 25% of beetle larvae. Parasitoids played a smaller role (less than 10% of larval mortality is due to parasitoids). Mortality in larvae and pupae can exceed 90%, but varied widely from one plantation to another. Examples of mortality tables are given for clearly characterized situations and they help to explain the stability of populations and the occurrence of outbreaks on a plantation or sites scale. Mortality rates lower than 98.6% can lead to population instability and an outbreak in an area.

No abstract