Laboratory screening of tropical hardwoods for natural resistance to the marine borer Limnoria quadripunctata: The role of leachable and non-leachable factors

The marine borer Limnoria ingests essential wood components including the extractives the wood contains. Some extractives may confer borer resistance on certain timbers. Feeding by Limnoria correlates with the rate of production of faecal pellets. The faecal pellet production rate and mortality on over 40 test timbers and non-resistant Pinus sylvestris sapwood was measured over 15 days. By placing animals in leachate from wood and with wood in flowing seawater, the effects of leaching-resistant and water-soluble compounds were measured. Some previously untested timbers affected Limnoria as strongly as timbers reputed for durability in marine construction. Wood of Minquartia guianensis, Nectandra rubra and Bruguiera gymnorhiza caused high mortality, and pellet production on them was less than 10% of production on P. sylvestris. Suppressed feeding rates, but with no heavy mortality, were observed on known durable species such as Chlorocardium rodiei, Dicorynia guianensis, Lophira alata and Nauclea trillesii, but also on Cynometra ananta, Distemonanthus benthamianus, Enterolobium schomburgkii, Goupia glabra, Hymenaea courabil, Mammea africana, Shorea sp. and Sacoglottis guianensis. Leachate from B. gymnorhiza, G. glabra, H. coubaril, N. rubra and Shorea sp. caused high mortality. These short-term bioassays thus detected clear differences between wood species in their resistance to Limnoria that matched findings from long-term marine trials, while indicating new species worthy of detailed testing.