Weed Management for a Healthy Orchard.
Weeds are a recurring management task in the orchard. If not managed properly, they can create competition among young trees, clog micro-irrigation systems, use and generate uneven irrigation and impede efficient harvest. Good weed management, starts with identifying the weeds in your orchard, routine monitoring, and identifying what tools will provide effective control of which weeds.
The University of California’s (UC) Integrated Pest Management (IPM) guidelines recommend the following actions for monitoring weeds:
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Survey your orchard for weeds in late fall and again in late spring.
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Monitor the orchard in a thorough fashion. Include the entire orchard as well as field margins, ditch banks and irrigation canals in your survey.
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Examine all areas that are susceptible to weed infestation, like areas of high moisture. Identify each weed species, location in the field, degree of control achieved with current tools, and which herbicides applied.
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Drawing a simple map so the infested sites can be monitored for weed control. Pay particular attention to perennial weeds and other problem weeds and note their location on the map.
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Record weeds found in rows and middles separately. Spot spraying to control weeds in tree rows is recommended. Leaving annual weeds in row middles — i.e. cover crops — can offer benefits for pollinators and soil quality.
Once you know what you’re dealing with, look to select herbicides or other control techniques based on what kinds of weeds are actually present in the orchard. The UC IPM website provides a comprehensive list of common and scientific names of weeds, along with photos and descriptions of each. You can find that list here.
In the late spring, the most important invasive weeds to look out for are perennial weeds. Preventing their growth in the rows or middles of the orchard. Common perennial weeds you’ll see are Bermudagrass, Johnsongrass, Dallisgrass, Nutsedges and White Clovers. Also, tufted perennial grasses such as threespike goosegrass are especially problematic during the beginning years of tree nut establishment due to their ability to reduce tree growth by competing for water, nutrients and sunlight. Once the almond trees reach their fourth leaf, established weeds can reduce harvest efficiency by making it more difficult to recover nuts from the orchard floor at harvest. The UC IPM website provides a late-spring weed survey form to help you identify these pests as June approaches.
Once weeds are properly identified and the correct herbicides are applied, it’s vital to control herbicide resistance by using a variety of weed-control strategies. Failure to do so can result in the rapid loss of an herbicide’s effectiveness — and there are very few new herbicide technologies in the pipeline.
As of 2021, there are 13 weed species that are commonly found in almond orchards throughout the California Central Valley. Each of these weeds have had confirmed cases of herbicide resistant biotypes in California. View those weeds and management options in the resource below.
