Rob Emery

European House Borer (EHB) Hylotrupes bajulus Linnaeus, is considered a serious invasive threat because it is a destructive pest of seasoned coniferous timber including pine, fir and spruce. If allowed to become established it can cause major structural damage to buildings. The pest is able to live in a variety of climatic conditions however it prefers temperate habitats. Methyl bromide is widely used for quarantine treatment but it is being phased out due to its listing as an ozone depleting substance. Furthermore, complete control of EHB with methyl bromide in timber at low temperatures and high moisture content is difficult. Currently, there are no known chemical or biological controls for EHB larvae in timber and wood packaging and the obvious way to reduce the quarantine threat posed by EHB is to develop reliable and effective means to disinfest wooden materials at the source. There is an urgent requirement for an alternative effective fumigant for the control of EHB larva in timber and wood. Ethanedinitrile (EDN) is a new fumigant (patented under the chemical name “cyanogen”) and it is known to be highly toxic to insect pests of timber and is fast acting. It is believed to have particular potential as a quarantine treatment for timber. EHB larvae of differing lengths were found to have varying tolerance to both EDN and methyl bromide with the larger EHB found to be more tolerant. In all experimental fumigations with larvae of a range of lengths and at varying exposure times (6 and 24 hours), EDN showed more toxicity than methyl bromide. EDN achieved 100% mortality at 40 mg/L, 25°C and 70% r.h. for 24 hours of exposure with timber blocks artificially infested with EHB. However, under the same experimental conditions, methyl bromide at 48 mg/L only achieved a mortality range of 97.3-100%.

Murdoch University Stored Grain Research Laboratory investigated the fate of 32P labelled phosphine in grain and grain fractions. Radioactively-labelled phosphine is a useful and sensitive tool to study residues of phosphine in grains and their fractions. This research will assist industry to improve phosphine fumigation practice. Five representative grains (wheat, barley, oats, canola and lupins) were fumigated with 32P labelled phosphine at 700 ppm and 25±2°C for two weeks exposure. Two types of residues were formed in grains from phosphine fumigation – phosphine residue and phosphine converted non-volatile residues. After one week exposure to atmosphere, the levels of 32P radioactive residue in the grains and their fractions were analysed. The results show that more than 85% of absorbed phosphine which was converted to non-volatile compounds cannot be removed by ventilation. Furthermore, 80-90% of non-volatile 32P residues were present in water and acid soluble extractions. Radiation imagery shows that more than 80% of 32P residues were located or distributed in the embryo, testa, pericarp and husk of wheat, barley, canola, lupins and oats. However, 90% of absorbed phosphine will be desorbed after one week exposure to the atmosphere.