purpose and field conditions (for rates of application for methyl bromide, refer to appendix B

for formulation and application rates for a desired crop).

 Methyl bromide is used with chloropicrin in various formulations as a preplant soil

fumigant. At low concentrations (up to 2%), chloropicrin is used as a marker for detection of

escaping fumes of methyl bromide. At higher concentrations, such as 33%, chloropicrin is used

as a fungicide (Noling and Overman, 1988). In Florida, two formulations are primarily used:

Brom-O-Gas (98% methyl bromide and 2% chloropicrin) and Terr-O-Gas (67% methyl bromide

and 33% chloropicrin).

 Immediately following bed formation, a polyethylene tarp (plastic mulch) must be

 applied. This mulch serves to reduce the loss of methyl bromide to the atmosphere as it

 vaporizes in addition to other horticultural benefits. In situations where plastic mulch is a

 component of the whole-systems approach, the plastic mulch is installed and remains throughout

 the life of the crop. There are several types of plastic mulch, depending on the use or purpose

 and time of the year installed. Growers may use plastic mulch that is gray, clear, white, black,

 or white laminated on black. For example, in the spring, the use of black plastic can raise soil

 temperatures to levels which are conducive to young plant growth. However, during the fall,

 the soil temperatures are already warm and the use of white plastic is preferred, because white

 plastic reflects light, resulting in cooler soil temperatures, as compared to black (Decoteau et

 al., 1989).

 The thickness of plastic can vary from .25 to 1.5 millimeter or thicker. Thicker plastic

 mulches correspond to greater decreases in atmospheric loss of methyl bromide. Other

 advantages of plastic mulch include increased weed control, increased moisture retention, and