How to Manage Pests

Soil solarization

Soil solarization is an excellent method for reducing some weed seeds and soilborne diseases. Solarizing involves leaving a clear plastic tarp on the soil surface for 4 to 6 weeks during the hottest part of the year. Soil solarization works well in warm growing areas and may be ineffective in foggy, low-light, or low-temperature areas.

To solarize, first level the soil and prepare the soil for planting. Roll tarps over the surface, smoothing out air pockets. Bury the edges of the tarp with soil. Strips may be placed so only the tops of planting beds are covered and furrows are left untreated. Wet soil immediately before laying down the tarp. When solarizing only the bed tops, it is best to apply water under the tarp with a drip system. Otherwise, the uncovered furrows will become quite weedy and special care will be required to keep plant parts out of the treated areas during weed removal. After solarization is finished, remove the tarp before planting. Tarps may be left on the soil and serve as a mulch for the crop by transplanting plants through the plastic, however, doing so may make conditions too hot for some plants, such as asparagus. Do not leave the tarp on for more than 6 to 7 weeks as it will become brittle and difficult to remove.

Use clear polyethylene plastic tarp 1 mil (0.001 inch [0.025 mm]) thick. Thicker tarps, 1.5 to 2 mils (0.038 - 0.050 mm), can be used in windy areas (avoid thicker 4 to 6 mils as they are more reflective and don't allow the soil to heat up as much).

For more information, see the Soil Solarization for Gardens and Landscapes Pest Note.