Third, take the time to test soils for nematodes and choose the strategy that best fits the specific nematode pressure in the field.

Moderate nematode pressures can be mitigated through the selection of resistant rootstocks, strip fumigation or cultural practices that include managing weeds for one to two years prior to orchard removal or rotating in a cover crop such as Piper Sudangrass. More severe pressures will require broadcast soil fumigation.

Soil fumigation strategies require several considerations that will be discussed in more detail in the May issue. Keep in mind, though, that traditional fumigation with methyl bromide has become very restricted, and what short supply is available in many cases has become cost prohibitive. In addition, other soil fumigants commonly used in almonds are now restricted by regulatory constraints, particularly in the San Joaquin Valley where air quality emissions are a significant concern.

Fourth, the most common issue when replanting almonds back-to-back will be replant disease. Replant disease stunts, and at times, kills young trees with roots that underperform at taking up water and nutrients.

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, particularly in coarser-textured soils that are more prone to the condition.

Switching rootstock parentage may provide some control, but may not be worth the sacrifice to horticultural benefits.

If fallowing is not an option for replant disease, consider fumigation with a strip-row or tree-site treatment with a fumigant that contains chloropicrin.

The Almond Board is currently funding research trials throughout the state to provide information about replanting older orchards that growers can integrate into their own decision-making. Field trials are looking at fumigation options to reduce pest pressures and emissions, field evaluation of almond rootstocks and varieties, and many other factors that will help growers make an informed decision.

For details on Almond Board-funded research and other related research projects in California, visit the Almond Board website at, click on “resources” and then “research reports.” For more on almond orchard fumigation, go to