Physical methods comprise a relatively small but important group of methods that are typically utilized either alone or in combination with cultural and chemical management techniques. Note that three of the four methods to be considered rely on the use of heat. As has been mentioned in several other units (e.g. recognizing a nematode problem and cultural control), temperature is an important factor in the management of nematodes. Each nematode has different maximum and minimum thresholds for activity, infection and growth and different maximum levels for survival.
Hot water treatments are conducted on planting stock to insure that nematode infested materials are not planted. At times, it is necessary to add a chemical to the hot water treatment bath to either enhance the effectiveness against nematodes or to minimize problems from fungal or bacterial infestations.
Steam sterilization is most often used to treat batches of soil to be used in pots or raised beds. There have also been attempts to develop equipment to treat entire fields. Soil solarization is in parenthesis to indicate that although it is often proposed as a method of nematode management, it use is limited by the depth to which the sun is able to heat the soil to levels lethal for nematodes.
Root pruning refers to the practice of removing nematode infested roots from bulbs prior to planting.