Temperature Records from Anaerobic Composting Experiment

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A field experiment was set up by Roland Quitugua to find out if sufficient heat could be generated in anaerobic composting to kill rhino beetles. Piles of rotting coconut material, potentially infested with rhino beetles, was enclosed in large bags.  Temperatures were recorded by Hobo® dataloggers buried in piles of decaying coconut material sealed in a plastic tarp.  Two (each) caged rhino beetle grubs and adults were buried in each pile.

It is obvious from the diurnal oscillations that most of the heating was from the sun, and not from the anaerobic decay process.  One most days temperature exceeded 40°C for a few hours with a maximum temperature of greater than 45°C.  The lethal temperature for scarabs reported in the literature is in the range of 40°C to 45°C, indicating that solar heating of rotting coconut material is probably sufficient to kill all rhino beetles feeding in it. However, none of the caged rhino beetle grubs and adults which had been buried in the piles were dead at the end of the five week experiment.  Note that temperatures measured in this experiment were much higher than those measured in covered piles at Faifai Beach in January 2008 (see attached PDF).

References

Davidson, R. L., J. R. Wiseman & V. J. Wolfe 1972. Environmental Stress in the Pasture Scarab Sericesthis nigrolineata Boisd. I. Mortality in Larvae Caused by High Temperature. Journal of Applied Ecology, Vol. 9, No. 3. (Dec., 1972), pp. 783-797.

"At moderate soil moistures the longest exposure to 30C (192 h) was harmless, and the shortest exposure to 40C (45 min) was lethal."

S. T. Hassan 1975. Effects of High Temperature and Soil Moisture on Survival of First-Instar Larvae of the Scarab Anoplognathus porosus (Dalman) (Coleoptera) The Journal of Applied Ecology, Vol. 12, No. 3 (Dec., 1975), pp. 749-754

"A laboratory experiment testing survival of first instar larvae of Anoplognathus porosus at high temperatures and various soil moistures is described. High temperature stress appears to begin above 32.5C. The mean survival over several durations of exposure suggests a gradually increasing mortality above 30C. The upper lethal temperature is considered to be 40C."

Denzel E. Ferguson; James D.  Some Temperature Studies on the Beetle, Popilius Disjunctus Land Ecology, Vol. 42, No. 1. (Jan., 1961), pp. 195-197.

"The upper lethal temperature for one hour exposure was approximately 45C, that for 12 hours exposure was approximately 39C."

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