Laboratory, greenhouse, and field validation studies were done in 1999 to augment the existing database of thermal death dosages of phytoparasitic nematodes. Field soil containing a mixed population of Meloidogyne incognita, (root knot nematode = RKN), Pratylenchus vulnus (root lesion nematode), and others were subjected to moist heat treatment simulating solarization at five temperatures - 42, 46, 50, 60, and 70 0C. These are temperatures which would be commonly achieved during solarization of field or containerized soil during the summer months in the warmer, inland areas of California. A significant achievement largely stemming from this project was accomplished during the past year. According to regulations of the Nursery Stock Nematode Control Program, CCR Sections 3055-3055.6 and Section 3640, the California Department of Food and Agriculture (CDFA) specifies treatment and handling procedures to ensure against nematode pest infestation of media (soil, etc.) used for nursery stock for farm planting. For many years, the only treatments approved for this purpose were methyl bromide fumigation and soil steaming. However, CDFA accepted our field and laboratory data showing that a specific type of solarization treatment could be used to reliably perform nematode disinfestation of container, flat, and frame grown nursery stock.. The approved treatment (excerpted from CDFA NIPM Item #12 ) is as follows: "Solarization of soil until the temperature of all the soil reaches a minimum of 158 F (70 C) that is maintained for at least 30 contiguous minutes. Soil must be either in polyethylene planting bags or in piles not more than 12 inches high. Soil in piles must be placed on a layer of polyethylene film, disinfested concrete pad, or other materials which will not allow reinfestation of soil, and covered by a sheet of clear polyethylene film. An additional layer of clear polyethylene film must be suspended over the first layer to create a still air chamber over the soil to be treated. Soil moisture content must be near field capacity. Soil temperature at the bottom center of the pile or bag must be monitored and recorded to ensure that the minimum temperature of 158 F (70 C) for 30 minutes is achieved. Following treatment, the soil and containers shall be protected from reinfestation by nematodes". |
Similar laboratory and field experiments on six weed species were repeated from the study done in 1998. It is expected that data collected during the project will be computerized and made available to end users through the UC/IPM web site. Users will be able to correlate soil temperature data from solarization at their farms with those from the database to help them make decisions on when the treatment has been of sufficient duration to kill a range of soilborne pests.