Almond growers have several issues to consider before replanting an orchard. At the 2010 Almond Industry Conference, UC Merced County Farm Advisor David Doll reviewed replant considerations, and said growers planning to replant an orchard should come up with a strategy they can afford that will give sustainable performance throughout the next generation.
A well-thought-out replant strategy will help replanted orchards get off to a better start and boost long-term production.
The first step in putting together such a strategy, Doll said, is to look at the orchard’s history.
Before pulling out an older orchard, look for weak spots by surveying the orchard on foot or obtaining visual images through resources such as Google Earth. Once these weak spots are identified, growers can address the causes of that variability through control strategies that include soil fumigation, rootstock selection and/or cultural practices.
Based on the orchard’s past history, replant problems can be separated into four general categories: 1) abiotic factors related to physical and chemical conditions; 2) aggressive pathogens and pests, such as Phytophthora, Armillaria, Verticillium and ten-lined June beetle; 3) plant parasitic nematodes; and 4) replant disease — a microbe-induced growth condition that is nearly universal in varying degrees to stone fruit orchards, such as almonds, replanted to previous stone fruit ground.
Variability as a result of physical and chemical conditions can be addressed through cultural practices such as soil modification or changes in management practices related to irrigation, nutrition and weed management systems.
Growers should address aggressive soilborne pathogens and pests through a combination of fumigation, cultural practices and resistant rootstocks. Take time to test soils for nematodes, and choose the strategy that best fits the specific nematode pressure in the field.
The most common issue when replanting almonds back-to-back will be replant disease. Research has shown that fallowing almond ground for at least one year prior to replanting or planting a non-host cover crop can provide a significant benefit for mitigating replant disorder. If fallowing is not an option, consider fumigation with a strip-row or tree-site treatment with a fumigant that contains chloropicrin. Fumigant options for specific situations will be reviewed later in this series.
For details on Almond Board–funded research and other replant-related research projects in California, visit AlmondBoard.com/ResearchReports.
This article, by the Almond Board’s Gabriele Ludwig and Bob Curtis, is a summary of the first in a series of articles on orchard replanting published in Western Farm Press. The complete article is in the March 19 issue, pages 12–13, and online (dated March 21) at westernfarmpress.com.