UC researchers have been reviewing spot fumigation techniques in almond orchards, evaluating the efficacy in test fields and considering the overall benefits to growers. The project is showing success in lowering cost and material use, along with helping growers conform to increasing environmental regulations.
Almond harvest is just about finished and growers looking to replant for next year have two major concerns to consider. The fungal microbial complex, Prunus replant disease, is a significant problem for growers primarily in the San Joaquin Valley as well as the Sacramento Valley. “The second problem is plant-parasitic nematodes and this includes ring, lesion and root-knot nematode,” said UC Cooperative Extension Pomology Advisor for Merced County David Doll.
Researchers have been working on fumigation trials in sandy soils that have been used for growing almonds for a significant amount of time. These soil types are particularly attractive environments for nematodes. Growers have historically opted for either a broadcast or row-strip application of Telone to address nematode concerns. Doll noted that “we’ve been working with TriCal and developing an experimental application of fumigants, pre-plant soil fumigants, in which we utilize spot fumigation.”
The research includes the use of a normal fumigation rig that has been equipped with a GPS guided controller and will only apply the fumigant when it reaches a predefined boundary established around a tree. “This allows us to reduce that fumigated area essentially from a row-strip application which is about 50 percent of the orchard, to a tree spot which is around 20 to 30 percent of the orchard depending on tree spacing,” said Doll.
Reducing the amount of material needed will naturally result in lower overall costs. Using fewer fumigants will also help growers meet the regulatory demands on pre-plant fumigants. “If we can cut our fumigant usage in half, we cut our emissions in half and we save farmers money in the process, I mean, it’s a win all the way around,” Doll stated.
Doll noted that data collected from two large trials over the past eight years in Merced County indicates this method of spot fumigation “is as effective as row-strip and broadcast applications in nematode infested and Prunus replant disease infested soils.”
Spot fumigation does have some limitations related to how the plantings are administered. Planting by hand will not necessarily provide the precision required by the fumigation rig to administer materials where they need to be. “But if you’re using GPS to help guide your planting or machine planting, the spot fumigation treatment is pretty effective,” said Doll.
Listen to the interview below.