of the fumigant through the soil pores will be blocked and result in reduced effectiveness, due

to lack of movement and dilution of the chemical by the presence of water (Munnecke and Van

Grundy, 1979).

 Soil type has also been found to influence the effectiveness of soil fumigation uses of

methyl bromide. Munnecke and Gundy (1979) stated that the more coarse and less compact the

soil, the more effective the fumigant is. Goring (1967) found that clays can absorb fumigants,

however, organic matter was implicated as the major source of absorption in the soil. Thus,

without an increase in application rate, high levels of organic matter can negatively influence

the effects of fumigation (Munnecke and Gundy, 1979).

 Soil moisture, as it affects organisms in the soil, is an important factor that influences

a fumigant's effectiveness. Munnecke, et al. (1959) found that at higher levels of relative

humidity, there was increased uptake of methyl bromide into the spores of Alternaria solan

resulting in enhanced efficacy. In other studies, temperature was demonstrated influence to the

effectiveness of fumigants. Munnecke and Bricker (1978) and Kenaga (1961) found that when

methyl bromide is applied under warmer temperatures, there was an observed increase in

effectiveness.

 Overall, plants have been observed to grow better in soils that have been fumigated.

Improved plant growth is due to the reduction in soilborne pest populations and/or disease

pressures, such as fungal pathogens, insects, nematodes and weeds. Exceptions, however, do

occur where plants do not produce or grow well in fumigated soils (Munnecke and Gundy,

1979). In some cases, poor growth responses occur due to reduced mycorrhizal propagule levels

in soil. Mycorrhizae are important in the uptake of some elements such as phosphorous. This