As we transition into the fall season and prepare for 2025, California avocado growers face a fresh set of challenges in maintaining grove health. From managing irrigation in the aftermath of a hot summer to mitigating pest threats and implementing soil preparation, this is a good time to minimize risks and promote the well-being of your avocado trees. 

Our field experts have come together with some essential insights and guidelines to help you safeguard your grove and optimize productivity for the season ahead:

Pests & Pest Control 

Pest control is crucial for avocado growers, who face various challenges such as potential thrip damage, fruit fly quarantines, gopher control, and managing pests like rats and squirrels. These pests can directly impact the health and productivity of avocado trees and affect the overall harvest. 

• As we wrap up the 2024 season, it’s a good time to check your pesticide and restricted materials permit status. Don’t want to wait until December and have a delay in getting your permit renewed. 
• After a year of high #2 output, there is concern that next year may present excessive thrip (scirtothrips perseae) damage again. Pesticide applications were delayed due to harvest and helicopter availability. The abamectin treatments for thrips are also helpful in controlling persea mites. These mites tend to attack weaker trees and thrive in dustier conditions like rows along access roads.  
• Another challenge this season has been the fruit fly quarantines overlapping avocado orchards. The Oriental fruit fly affects harvest in Redlands/Riverside, and the Queensland fruit fly affects Simi/Santa Rosa Valley. West Pak works diligently with state and county officials to help growers navigate their harvest. 
• With the decreased availability of some baits, it has become challenging for growers to control gophers. Many have gone back to trapping, which although labor intensive can be highly effective.  
• Controlling rats and squirrels in the orchard is important. These pests can directly impact your packout cull rate. Tamper-resistant bait stations can be useful for placing the appropriate treatment.

Fertilization and Soil Prep

Soil preparation and fertilization are important this time of the year as it helps to ensure the health and productivity of your avocado trees. By preparing the soil, you can address issues such as nutrient depletion, moisture regulation, and root disease prevention. 

• Growers who experienced a large crop this past season should think about applying potassium, which has been depleted throughout the season. 
• This is a good time to get your leaf analysis done to check the nutrient levels of your trees and overall tree health.
• Root disease is a constant battle. Phytophthora Cinnamomic is present in many orchards. Growers need good irrigation practices that limit extremely dry and wet cycles. While we are in our early fall root flush, it is a great time for Phosphite applications with your irrigation. There are newer products on the market like Orondis that have shown success.

Irrigation Best Practices

As temperatures cool, avocado trees require careful attention to water management. Even though the heat of summer subsides, dry conditions can still persist. 

• Adjust irrigation schedules to account for reduced water demand as daylight shortens. 
• Avoid over-irrigating, which can lead to root rot, particularly in heavier soils or during cooler temperatures.
• Micro-sprinkler systems are especially beneficial during fall and winter as they allow for precise water application. 
• Ensure that all irrigation systems are properly maintained and ready to handle winter rains or emergency watering needs during potential frost events.

Fire Hazard Management

Fire season can still pose a threat, especially in windy fall months. Defensible space around avocado groves is critical for fire prevention. Key actions include:

• Weed Management: Clear vegetation, dry grass, and plant debris from around trees and structures.
• Pruning: Regularly prune low-lying limbs and remove dead wood to reduce fuel for fires.
• Wood Chips: If using wood chips for mulching, ensure they are spread thinly and not stored in large piles, as these can smolder if ignited.
• Sprinkler Systems: Use metal pipes and risers in sprinkler systems to minimize fire risk. In the event of a fire threat, preemptively applying water can create a moisture buffer around the grove.

Wind Damage Prevention

Fall also brings seasonal winds that can cause both physical damage to trees and scarring of fruit. The following measures can mitigate wind damage:

• Windbreaks: Planting windbreaks around groves reduces wind intensity. While they consume water and space, they can protect trees from losing fruit or sustaining structural damage.
• Staking Young Trees: Secure young trees in windy areas with stakes to prevent them from rocking, which can damage their roots.
• Tree Shape Maintenance: Regularly prune trees to maintain a shape that reduces wind resistance, preventing them from acting like sails in high winds.

Preparing for Cooler Weather and Frost

As winter approaches, especially in areas like Southern California where frosts and freezes can occur, growers need to be proactive in frost protection.

• Frost vs. Freeze: A frost occurs when the ground radiates heat and cold air settles near the surface, while a freeze happens when cold air masses move in, lowering temperatures throughout the atmosphere. Frost conditions can often be managed with wind machines or micro-sprinklers, but freezes are more challenging, requiring the addition of heat via orchard heaters.
• Wind Machines and Orchard Heaters: Wind machines are effective in frost conditions with a temperature inversion, but avoid their use in freeze conditions, where they may spread cold air rather than displace it. Heaters can provide warmth, though they can be costly and pose a fire risk.
• Micro-sprinkler Usage: During frosty nights, micro-sprinklers can help mitigate damage by releasing heat when water freezes and later melts at sunrise. Be sure to run the sprinklers until sunrise if temperatures drop below 32°F.
• Protecting Young Trees: Younger trees are more vulnerable to frost than mature trees, so use insulative wraps or burlap covers to shield them from frost.

West Pak’s field team is here to help growers ensure a productive season. If you, as a California avocado grower, have any questions or concerns, please contact your local field rep.