Submitted to: Pest Management Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/14/2005
Publication Date: 5/24/2005
Citation: Allaire, S.E., Yates, S.R., Zhang, Q., Ernst, F.F. 2005. The potential efficiency of irrigation management and propargyl bromide in controlling three soil pests: Tylenchulus semipenetrans, Fusarium oxysporum and Echinochloa crus-galli. Pest Management Science. 61:799-808. Interpretive Summary: Methyl bromide is highly efficient in controlling pests in soil, but will be phased out in 2005 because it depletes stratospheric ozone. There is an urgent need to develop alternatives for methyl bromide. Propargyl bromide (3BP) is a potential alternative and degrades more rapidly in soil and has a lower vapor pressure, thus poses a lesser risk of adverse side effects. There is currently little information concerning 3BP’s effect on plant pathogens. One objective of this research was to estimate several measures of lethal dose (e.g., LD50, LD90) and the concentration time index for several important plant pests. These include a nematode (Tylenchulus semipenetrans), barnyardgrass (echinochloa crus-galli), and a fungus (Fusarium oxysporum). Another objective was to compare the efficiency of four different formulations of 3BP in controlling the plant pests. A third objective was to compare the effect of different irrigation management practices on the 3BP concentration in the control zone around the injection point. This type of information is needed to determine if 3BP would be an effective alternative to methyl bromide.
Technical Abstract: 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 oC 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 ug/g soil for the nematode, 3 ug/g for the grass, and 9 ug/g for the fungus. The concentration–time index for killing 90% of the population (CT90) was 11 ug/g h for the nematode, 112 ug h/g for the grass and 345 ug h/g 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).