Effects of high-temperature treatment on root knot nematode and Fusarium wilt in continuous cucumber cropping soil

Objectives Continuous cucumber cropping causes severe and widespread root knot nematodes and blight . High temperature shed sealing in the summer greenhouse fallow period is one of the safe and effective ways to solve this problem. This study simulated high temperature shacks to treat soil at different temperatures. We monitored changes in root-knot nematodes and blight to provide theoretical support for greenhouse high temperature disinfection with sunlight.

Methods This experiment used the soil of the continuous cropping 1–19 crops of ‘Jinyou30’ cucumber variety. First we detected the dynamics of root-knot nematode and Fusarium wilt in different cucumber continuous cropping systems and populations of the two pathogens in soil. Secondly we carried out the high-temperature treatment to the 17^th crop soil at 45℃, 50℃, 55℃and 60℃. Finally, we measured and compared the changes of the number of pathogens in the soil treated with different temperatures, and carried out cultivation experiments on high temperature treated soil, followed by measuring the incidence of both diseases and the growth indicators of the plants and did comparison.

Results With more crops of cucumber continuous cropping, the population of root knot nematodes and Fusarium oxysporum in the soil increased gradually. By the 17^th crop, the incidence of both diseases and the number of corresponding pathogens reached the highest (or second highest) level. The 17^th crop soil was treated with the high temperature of 45℃–60℃. With the increase of soil treatment temperature, the number of root knot nematodes and Fusarium wilt was both reduced. When the treatment temperature reached 55℃, root-knot nematodes in soil killed completely, and killed Fusarium oxysporum was killed simultaneously when the temperature reached 60℃. The degree of occurrence of root knot nematode and blight in cucumber seedlings cultivated with high temperature trented soil was also reduced with the increase of treatment temperature. When the soil treatment temperature reached 50℃ and above 60℃, root knot nematode and Fusarium wilt was completely controlled. In addition, when the continuous cropping of cucumbers was planted on the soil treated with 60℃, the late plant growth index and seedling index in late growing stages became significantly better than the control.

Conclusions The increase in soil-borne diseases with continuous cropping was mainly due to the accumulation of pathogens in the soil. High temperature treatment above 55℃ to soil before planting can effectively reduce or even completely kill root-knot nematodes and Fusarium oxysporum in soil, thereby reducing or eliminating the occurrence of these diseases.