Effects of heartwood extractives on symbiotic protozoan communities and mortality in two termite species

- Heartwood extractives of durable wood species from Pakistan were evaluated against two termite species.
- Mortality of termites increased with increased extractive content in filter paper assays in a dose dependent manner.
- Extractives have protozoicidal activities.
- Chemical characterization using GC-MS identified major components of these heartwood extractives and are discussed relevant to the findings.

Lower termites (Isoptera: Rhinotermitidae) are considered severe pests of wood in service, crops and plantation forests. Termites mechanically remove and digest lignocellulosic material as a food source. The ability to digest lignocellulose not only depends on their digestive tract physiology, but also on the symbiotic relationship between termites and their intestinal microbiota. The current study was designed to test the possible effects of four heartwood extractives (Tectona grandis, Dalbergia sissoo, Cedrus deodara and Pinus roxburghii) on the mortality, feeding rate and protozoan population in two lower termites, Reticulitermes flavipes and Heterotermes indicola. All wood extractives tested rapidly lowered protozoan numbers in the hindgut of termite workers, which was closely correlated with worker mortality. The average population of protozoans in both termite species was diminished in a dose-dependent manner after fifteen days feeding on treated filter paper. Mortality of termites increased when fed on filter paper treated with T. grandis or D. sissoo heartwood extractives with minimum feeding rate at the maximum concentration (10 mg ml−1). Protozoan number and termite survival was also compared with starved termites and results showed that protozoan populations ware reduced up to 99.60 and 65.71% in R. flavipes and H. indicola, respectively as compared to untreated filter paper controls with ≅ 80% survival for both termite species. Characterizations of heartwood extractives were performed using Gas Chromatography-Mass spectrometry (GC-MS) and chemical profiles were obtained for extractives from each wood species. The largest chemical components, based on percentage of sample, identified from T. grandis were Squalene, 2-methyl-9, 10-Anthracenedione and 1-Methyl-3,4-dihydroisoquinoline. Trismethoxyresveratrol, 1, 3-Diamino-8-n-butyl-5, 6 dihydrobenzoquinazoline and 6, 8-dimethyl-Benzanthracene were the largest components from D. sissoo. The largest percentage components from C. deodara were (E) - Atlantone, Di-epi-alpha-cedrene and alpha-Cuprenene. The main components of P. roxburghii were identified as 1, 2, 3, 4-tetrahydro-5, 8-dimethyl-Acridin-9-amine, 2, 3-dihydro-5, 7-dihydroxy-2phenyl-4H-1-Benzopyran-4-one and 5-hydroxy-7-methoxy-2-phenyl4H-1-Benzopyran-4-one. These are discussed in terms of their termiticidal and protozoicidal properties.