Blight in a garden makes for a disappointing growing season. Caused by microorganisms that prey off plants, the end results are poor fruiting and even dead plants. Several methods can control blight including rotating crops on a regular basis, buying resistant plants, and using chemical controls that kill the responsible bacteria. One method that has proven effective and environmentally friendly is solarization -- using the sun's light to heat the soil high enough to kill the blight-producing bacteria.
Cut the plastic to fit the garden's size, with about 12 inches on the margins. If the plastic is in strips, then use a glue that is heat tolerant to create a single piece large enough for the garden. Roll the plastic up like carpet along it's widest edge.
Clean the garden of all debris such as weeds, leaves and plant remains. Rake the garden as smooth as possible, leveling it to ensure no mounds or valleys.
Water the garden soil until it is thoroughly drenched. Be careful to use a gentle setting on the watering to ensure it does not create any depressions when it hit the soil.
Lay the rolled plastic directly onto the ground at the garden edge so that when it unrolls it covers the garden. Unroll a few inches and tack down the now uncovered edge of the plastic with stakes, soil, bricks or other weight.
Unroll the plastic onto the garden, covering it completely and leaving no air pockets under any portion. If at all possible, avoid walking on the ground and compressing the soil.
Tack down all the sides of the plastic to ensure no air can seep under the edge.
Leave the plastic on the garden for a week to six weeks, depending upon the season and the weather. The spring sun in a temperate climate can heat the soil to approximately 130 degrees F and sterilize the soil 4 to 6 inches deep over several weeks. The hotter summer sun can reach 160 degrees and do the same job in one week.
Remove the plastic and, when the soil cools down, set out the plants as normal. The microfauna that you want for the benefit of the soil and plants will begin to reestablish themselves quickly.