June 2010. From India, an intriguing observation that infestations of rhinoceros beetle on coconut is twice that on oil palm of the same age and in adjacent plantations. The higher lignin composition of coconut compared to oil palm apparently did not affect the beetle.
Is coconut more attractive to pests in general, a member asked? It evolved by floating between coasts and islands and may not have been exposed to pests that could not make the same long ocean journeys. Perhaps, it has spineless stems and leaf stalks because it didn’t need to develop defence mechanisms?
The oil palm, in contrast, evolved in the African jungle, with tropical rainforest pests.
It was also speculated that there may be differences in the occurrence of lignin between the two palms, and this, if it occurs, could be related to defence against insects. It was said that oil palm had larger amounts of cellulose and less lignin. A photo was sent with a coconut damaged by rhinoceros beetle next to healthy oil palms.
In addition to the comments on why coconuts are preferentially attacked compared to oil palm, a member mentioned that in the Suva/Nausori area of Fiji, Oryctes is not a serious problem. There, the beetles seem to prefer decomposing vegetation. In response, it was said O rhinoceros has evolved along with coconut as its host. The oil palm is a West African palm with different structure of leaf bases and presumably a different smell to coconut. One of the reasons for the low incidence of damage of palms in the Suva/Nausori area is the lack of dead palm trunks and other debris. Years ago all the street trees in the area were treated with BHC powder to control the beetle. Worst damage is in areas where many palms have been blown down in hurricanes, two or more years after the event, as well as near sawmills where the beetles breeds in the large piles of sawdust.