Soil born diseases are caused by many things, most commonly, nematodes or fungi and they are very hard to control with conventional pesticides. Fortunately, there is a method gardeners can use to help clean up the soil - Soil Solarization.

Soil solarization uses radiant heat from the sun, collected through clear plastic to heat the soil to a temperature that kills pest, fungi, nematodes, weeds, weed seeds, and others. Research has shown that soil temperatures may rise in excess of 130 degrees F up to 6 inches deep. It is a simple process, one that requires sun and heat - things we have on the Treasure Coast, and time. The best time for this process in Florida is during June, July, and August when we have the hot sun needed for solarization.

Preparation is important. Soil must be well tilled to destroy clods and plant debris so heat conduction will be uniform through the soil. Air pockets could prevent the heating of the soil around the air pocket. Moisture of the soil should be high, as wet soil conducts heat better than dry. Also, most pest organisms are more affected by the heat in moist soil. Prepare the soil as for your next garden or planting.

Use clear polyethylene plastic, not black. Clear plastic allows the soil temperatures to rise faster and higher because sunlight passes through clear plastic to heat the soil directly. Thin plastic (l to 2 mil) rather than thick (6 mils) has been reported to favor deeper control of soil-borne fungi faster, but both eventually provided equal control and thicker plastic is less likely to tear. Be sure that the edge of the plastic is covered with soil. A trench around the garden will help in providing a seal for the plastic. This seal will help keep heat and moisture in.

Soil should be covered for at least 4-6 weeks, the summer is ideal for Florida, the air and soil temperatures are at their highest. Leave the plastic in place until planting time and do not till or disturb treated soil before planting. Avoid bringing contaminated plants or untreated soil into the treated bed.

Your new plants will appreciate the clean soil that solarization has provided!

Carol