The potential efficiency of irrigation management and propargyl bromide in controlling three soil pests: Tylenchulus semipenetrans, Fusarium oxysporum and Echinochloa crus-galli.

Propargyl bromide (3-bromopropyne, 3BP) is a potential alternative for methyl bromide. Little information is available about its efficiency in controlling pests. The purpose of this paper is to estimate the 3BP dose required for killing three pests and to compare the efficiency of water management approaches to that of fumigation. The pests, Fusarium oxysporum Schlecht (fungus), Echinochloa crus-galli (L) Beauv (grass) and Tylenchulus semipenetrans Cobb (nematode) were exposed to different 3BP concentrations in a sandy loam at 30 degrees C in a closed system. The lethal dose for killing 90% of the population (LD90) was calculated from the total applied mass, and varied from 0.3 microg g(-1) soil for the nematode, 3 microg g(-1) for the grass, and 9 microg g(-1) for the fungus. The concentration-time index for killing 90% of the population (CT90) was 11 microg g(-1) h for the nematode, 112 microg g(-1) h for the grass and 345 microg g(-1) h for the fungus. 3BP seems as efficient as other fumigant alternatives in controlling these pests. Using an open system, it was shown that the volume of soil in which the pests were controlled varied for different irrigation managements. Even 96 h after fumigation (with a concentration 10 times higher than would potentially be applied in the field), more than 20% of the soil volume had not reached the fungus and grass CT90 of the non-irrigated soil. The soil underneath the furrow and the bed reached CT90 only slowly in all irrigated treatments even though techniques for increasing efficiency were used (tarping, surface sealing with water and high application rate).