Extreme Temperature Switches Eliminate Root-Knot Nematodes: A Greenhouse Study

Root-knot nematodes (RKNs) severely affect the yield and quality of vegetable crops. While some chemical pesticides can effectively eliminate RKNs, they leave behind significant pesticide residues in vegetables and soil that are potentially harmful for humans. Research suggests that dormant RKNs in the soil become active in the presence of a host, upon which they become sensitive to extreme temperature changes. Here, we tested a novel method to eliminate RKNs (Meloidogyne incognita) in a greenhouse setting. RKNs were first activated by water spinach, at which point the soil was heated by natural sunlight and suddenly cooled by the addition of dry ice. This rapid change in temperature eliminated >90% of activated RKNs. After the temperature treatment, the physical features of soil did not change; however, soil porosity, available potassium content and soil invertase activity increased markedly. The treated soil was then used for cucumber planting to test its viability. Compared with cucumber plants grown in untreated soil, plants in treated soil had higher, thicker, and stronger shoots, and higher photosynthetic ability. Cucumber plants grown in untreated soil were severely infested with nematodes while few plants grown in treated soil had root knots containing nematodes. Based on these findings, we suggest that host plant induction followed by switched temperature treatment is an effective, easy, safe, and cost-effective method for eliminating RKNs.