Evaluation of dry ice as a potential cryonematicide for Meloidogyne incognita in soil

Solid CO2 (dry ice) was added to pots containing soil that was infested eit her with eggs of the root-knot nematode, Meloidogyne incognita, or with tom ato (Lycopersicon esculentum 'Rutgers') root fragments that were infected w ith various stages of the nematode. Two hours after dry ice was added, ther mocouples in the soil recorded temperatures ranging from -15 degrees C to - 59 degrees C. One day after treatment with the dry ice, the temperature of the soil was allowed to equilibrate with that of the greenhouse, and suscep tible tomato seedlings were planted in pots containing infested soil treate d or untreated (controls) with dry ice. After 5 weeks, roots were removed f rom the pots and nematode eggs were extracted and counted. Plants grown in soil infested with eggs and receiving dry ice treatment had less than 1% of the eggs found in the controls; plants from soil infested with root fragme nts and receiving dry ice treatment had less than 4% of the eggs found in c ontrols. Dry ice used to lower soil temperature may have potential as a cry onematicide.