Soil Solarization for Nematode Management

Sandy and loam soils, such as those found in the Florida home garden, are subject to the ravages of nematodes, wilt viruses, damping off, root rots and molds. While there are chemical solutions to some of these common plant problems, others are difficult if not impossible to control by other means. Soil solarization is a simple, environmentally-friendly, and safe way to prepare soil for a home garden that is free from parasites and disease.

How Does Soil Solarization Work?

During the hottest summer months of the year, garden soil is covered by a layer of thin, clear plastic for at least 6 weeks (the longer the better to ensure sufficient temperatures). The plastic is completely sealed (buried) into the soil at its edges. Black or other colored tarps or materials do not provide adequate solarization. It is the nature of the transparent plastic that allows for the high temperatures (up to 140 degrees F) necessary to cleanse the soil. Dark or translucent films end up reflecting too much heat, rather than trapping it.

The soil should be cultivated, made flat and watered well before solarizing. A high moisture content will make the organisms more susceptible to thermal damage. Care should also be taken not to allow the plastic to become punctured or loosened as the heat will escape.

Controlling Nematodes in the Home Garden

Although heavy rain, humidity, and overcast skies can lower the effectiveness of soil solarization in Florida, this practice still generates quite a lot of success in lowering nematode populations. In fact, since there are no pesticides available for home use that are effective against nematodes, soil solarization is one of the few weapons a Florida home gardener has against these microscopic pests.

In addition to soil solarization, organic home gardeners can plant nematode- or disease-resistant crop varieties and also practice crop rotation. Amending the soil well after solarization will help replace any nutrients lost in the superheating process.

Disadvantages to Soil Solarization

The biggest disadvantage to this soil management practice is that the intense heat kills beneficial organisms as well as it kills harmful ones. However, these populations do tend to recover quickly during the growing season. Environmentally-speaking, soil solarization does produce large amounts of plastic waste, but undamaged plastic may be re-used for the next season. And if solarization is used in place of pesticides and/or fungicides for controlling wilt viruses and other plant diseases, there is a positive environmental impact to offset the negative.

For more information on growing a vegetable garden in Florida, check out the Florida gardening best practices or visit the University of Florida’s Institute of Food and Agricultural Sciences.