Oryctes monoceros is the most serious pest in coconut plantations, causing up to 40% damage in tropical Africa, especially in Ivory Coast. With a view to reducing pest populations by olfactory trapping, field trials were carried out to assess the efficiency of a synthetic aggregation pheromone: ethyl 4-methyloctanoate (1), 4-methyloctanoic acid (2), a related volatile produced by males, and decaying palm material, either oil palm empty fruit bunches (EFB) or pieces of coconut wood (CW) of various ages. Vertical polyvinyl chloride tube traps (2 x 0.16 m with two openings in the upper half), embedded in the soil, were more efficient than 30-L pail traps 1.5 m above ground. EFB, which were inactive alone, synergized captures with synthetic pheromone. CW was more effective than EFB in comparative trials. Compound 2 did not catch any beetles when assessed with EFB, and reduced catches by 1 + EFB when tested at >10% with the pheromone. Trapping over 6 mo in 2002 and 2003 in a 19-ha coconut plot inside a 4,000-ha oil palm estate reduced damage from 3.8% in 2001 to 0.5% in 2002, then to 0.2% in 2003. Damage was 0.0% in 2004 with routine trapping using 32 traps, which caught 3369 beetles in 9 mo. The results are discussed in relation to other Dynastid palm pests and coconut protection in Ivory Coast.
Several palm plants have social and economic roles worldwide by providing drinks from their sap. In Côte d'Ivoire, management of the coconut sap is not yet practiced. In this study, parameters related to production of sap have been assessed from four coconut cultivars namely PB 113 + and PB 121 + hybrids and WAT and MYD varieties. From all the unopened inflorescences (spathes) studied into the coconut crown, whose ranks varied from 7 to 9, that of rank 8 yielded the highest volume of sap. From this spathe, the PB113 + hybrid provided the best yield of sap (61.81 ± 20.41 l). Most important proportion of that sap volume was recorded at the morning harvesting. The sap production duration of a spathe varied from 24 ± 1.87 days (MYD) to 46.78 ± 1.86 days (PB 113 + ). That duration depended on the length of spathes and regular sap flow allowed by them. Furthermore, the PB 113 + had the highest number of fruits (NBF = 174.33 ± 78.45 fruits). The results showed that volume of sap available is closely related to the length of production (r = 0.78) and the cultivar's nut yield (r = 0.82). The use of PB 113 + hybrid which provided highest quantity of sap is recommended for promoting the production of coconut sap in Côte d'Ivoire in order to improve the benefits derived from this plant.
Oryctes monoceros is a serious coconut pest, causing up to 40% damage in tropical Africa. Synthetic aggregation pheromone, ethyl 4-methyloctanoate, has been used to lure adults to traps. Traps with pheromone plus decaying palm material captured a high proportion of males. This raises the question whether individuals, which damage palms are receptive to the pheromone. We studied the sex ratio of the insects feeding on coconuts and those attracted to pheromone traps. Sixty two percent of adults from feeding galleries on living coconut palms were females. Pheromone with rotting palm material lured 43% females. To investigate the reasons for this difference, we compared the reproductive system of females lured to the odour traps or feeding in coconut galleries, or present in old rotting stems. Ninety six percent of the females trapped by pheromone had mated, and were sexually mature. In the galleries on living palms, 46% of females were immature, and 24% had not mated. In old rotting stems where eggs are laid and larvae develop, a mixture of 52% mated and 48% virgin females was found. Therefore, the pheromone together with the odour of rotting coconut stems signals a reproduction site to beetles, particularly mature females. In practice, the pheromone-baited traps will help in reducing the dissemination of gravid females, but will not affect directly the numbers of immature ones attacking palms. Our results show that when using pheromones for monitoring or controlling insects, the physiological status of the insects may have unexpected effects on the outcome.
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