- Author: Ben Faber
Manipulating the Avocado & its Environment
for Optimum Temperature & Light
California Avocado Society, California Avocado Commission & UC Cooperative Extension
AVOCADO GROWER WEBINAR
Tuesday, Aug. 17
9-11 a.m.
Register Here: https://us02web.zoom.us/webinar/register/WN_kByWCEvfTC-TwZgjmSWptw
And if you want to hear about irrigation from another viewpoint - greenhouses and berries - which is still good information for avocado growers, check out
|
|
And Wait, there's MORE!!!!!!!!!!
|
|
|
|
|
|
|
- Author: Ben Faber
** HLB Update **
for San Diego County Citrus Growers and Affiliates
The California Department of Food and Agriculture (CDFA) and the United States Department of Agriculture (USDA) have confirmed the first detection of Huanglongbing (HLB) in San Diego County. The disease was detected in a lemon and orange tree in a residential Oceanside neighborhood. This detection triggers a 5-mile HLB quarantine to restrict the movement of citrus, a mandatory survey, and treatment of all citrus trees within 250-meters of the site. Owners of commercial properties (25 or more citrus) in the HLB quarantine can expect to be contacted by state officials and your grower liaison, Sandra Zwaal szwaal2@gmail.com for next steps. The full CDFA press release can be found in the CDFA website.
Now more than ever, citrus growers need to inspect their trees for signs of HLB, the Asian citrus psyllid (ACP), and keep up with ACP area wide treatments! To determine if your location is in the HLB quarantine, visit the interactive HLB quarantine map. To see if you require mitigation to move your citrus, please review this Information for Citrus Growers/Grove Managers in an HLB Quarantine document. A detailed CDFA response to an HLB detection can be found in the CDFA Action Plan for ACP and HLB. A summary can also be found in this flyer.
A hybrid San Diego ACP Grower Workshop will be held in-person and on Zoom on August 26, 2021 (9-11am) at the Fallbrook Public Utilities District. The workshop will cover the impact of the HLB quarantine and to provide ACP and HLB information. The workshop is free to attend. Register here for this workshop.
ACP TREATMENTS
The San Diego County ACP Fall area wide treatments begin August 30 through September 13. If you have not already done so, please schedule your fall ACP treatment with your pest control company. To reduce risk of HLB, keep ACP populations low. Research has shown that ACP area wide treatments are designed to keep ACP populations low. Additional best practices per the University of California include monitoring your citrus for ACP populations. They are an excellent resources on how to monitor ACP and provides a list of ACP-effective materials specifically recommended for ACP area wide or coordinated treatments.
NEGLECTED/ABANDONED & REMOVED CITRUS
Unattended or abandoned trees can harbor breeding populations of the ACP and infect neighboring citrus with HLB. If you are unable or unwilling to care for your citrus, please consider removing them to help protect neighboring citrus. Removed, neglected, and abandoned citrus should be reported to the San Diego County Dept. of Agriculture, Weights & Measures CQP.AWM@sdcounty.ca.gov or by calling them at either (858) 614-7770 or (858) 694-2739. For tree/orchard removal or pest control referrals, please contact Sandra Zwaal szwaal2@gmail.com or (949) 636-7089.
UPCOMING EVENTS San Diego Citrus Grower Workshop
The workshop will cover the impact of the HLB quarantine and to provide ACP and HLB information. Held in-person and on Zoom at the Fallbrook Public Utilities District. The workshop is free to attend.
Aug 26 (9-11am) - In-person & Zoom registration
Citrus Pest & Disease Prevention Program (CPDPP) Meetings
The Citrus Pest and Disease Prevention Program (CPDPP) meetings are free and open to the public. The virtual meeting agendas and minutes are posted in www.cdfa.ca.gov/citruscommittee/. Click on the links below to register for meetings:
Aug 11 (9am) – CPDPC Full Committee Meeting
USEFUL RESOURCES
Citrus Pest and Disease Prevention Program (CPDPP) Committee Members
Information for Citrus Growers/Grove Managers in an HLB Quarantine
HLB Voluntary Best Practices
San Diego Ag Commissioner's Office
UC Scientific Research Summaries for ACP/HLB
UC Science-based analyses to guide policy decisions, logistics, and operations:
UC recommendations for ACP management and treatment options
Citrus Insider
Please feel free to contact me with questions.
Sandra Zwaal
ACP/HLB Grower Liaison for San Diego County
Szwaal2@gmail.com
(949) 636-7089
- Author: Ben Faber
Thinking about the weather and what others are thinking about it. Here's some websites that have caught my eye. Check them out, starting with the Alerts.
Alerts
https://www.readyventuracounty.org/vc-alert/
https://twitter.com/NWSLosAngeles
https://www.readyventuracounty.org/
Weather Climate Discussions
National Weather Service
https://www.weather.gov/losangeles
Daniel Swain – Weather West
SCRIPPS Center for Weather Forecasting
University of Washington weather forecasting
https://cliffmass.blogspot.com/
CA Avocado Commission weather – click on GreenSheet download
https://www.californiaavocadogrowers.com/publications/greensheet
Climate Change Assessment for Southern California
Good Weather and Water Podcast- UCANR
https://www.watertalkpodcast.com/
Atmospheric Rivers
https://water-talk.squarespace.com/episodes/episode-11
Collaborative Weather Monitoring
Air Quality
Climate Change Assessment for Southern California
And What Do You Need to Do About Heat, if a Grower
Why and How to Cool Avocado Trees
Mitigating Heat in the Orchard
Connecting to the Changes Around Us
With Climate Change Will We Grow Cactus?
Heat, Wind, Freeze, Wind, Repeat
Alli Rowe-Fish and Ben Faber
Cover crops offer an important opportunity to build soil health in avocado orchards. A cover crop is a crop seeded or encouraged as natural plant cover as an investment in soil fertility and not as a cash crop. Most cover crops are grasses, legumes, brassicas or a mixture and serve to protect bare soil while improving soil physical, chemical, and biological properties.
Benefits of cover crops
Perennial systems, trees in the ground for long periods of time, are unable to harness the benefits of crop rotation that include improved nutrient cycling, soil tilth, soil physical properties, weed and pest suppression, and erosion control. By cycling cover crops, growers of tree crops can mimic crop rotation on a portion of the land surface and maximize benefits in an orchard system.
The benefits of cover crops in California avocado orchards include:
- Improved soil structure;
- Reduced soil compaction;
- Reduced soil erosion from wind and rain;
- Increased soil organic matter content;
- Improved nutrient cycling;
- Weed suppression;
- Creation of habitat for pollinators and beneficial insects;
- Improved water infiltration
- Improved soil moisture storage
- Increased soil aeration
- Disease suppression.
California will continue to experience increased intensity and duration of drought and heat stress days. These environmental conditions dramatically impact fruit set and viable production of avocados. Improving soil health builds resiliency to climatic conditions and allows farmers to continue to grow in the face of climate change. A specific consideration is improved water infiltration achieved by cover cropping in orchards. The enhancement in soil structure due to the presence of varying depths of roots allows for precipitation to infiltrate rather than run off. By keeping precious precipitation on the orchard property, growers become more resilient in the face of drought and heat. Improved infiltration by rain water can improve salt leaching and reduce salt stress on the tree.
Selecting a cover crop
The main consideration in selecting a cover crop is to identify the purpose and objectives for its use. Table 1 identifies specific goals and considerations for cover cropping. Most avocado growers in California will opt for a winter cover crop to harness winter rains to avoid irrigating. Therefore, the following selections are geared towards winter cover crops and do not go into detail for summer cover cropping.
Cover crop mixes may be more expensive than single species covers such as only a brome or a medic, but satisfy multiple purposes in one planting and often see successful establishment and growth rates. They may provide better cover, weed suppression, and biomass, especially during drought or other non-optimal growing conditions. In addition, mixes supply multiple nutrients and benefits beyond a single species. For example, a mix that includes triticale, faba bean, and daikon radish sees the benefit of soil stabilization and infiltration from all three species, increased carbon content from the triticale, nitrogen fixation from the faba bean, and reduced soil compaction from the radish.
In selecting a cover crop, it is critical to consider any pests that may be encouraged with certain species. For example, many avocado growers are constantly battling gophers in young orchards. Gophers love clover varieties, so if you already have more gophers than you can handle, consider choosing a cover crop mix that does not contain clovers. There does not appear to be an increase of ground squirrel activity with covers (https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1020&context=vpc17).
Table 1. Cover Crop Categories and Considerations
Seeding timing
The timing of cover crop seeding will vary based on location and operational goals. However, flexibility is key for getting cover crops seeded at the right time to maximize winter rainfall for good establishment. Many cover crop seed companies will recommend seeding in fall, October or November. In Central and Southern California, that time frame tends to be hot, dry, and windy – not ideal conditions to seed a cover crop. The best time to seed would be right after the first rains come to loosen the soil and provide a bit of moisture. The key to success lies in watching the weather and being able to jump on a window between early rain events.
Frost can be a consideration for many avocado growers in Central and Southern California. Early establishment of tall cover crops can increase risk of frost exposure and should be avoided. To get around frost issues, seeding later in the fall and early winter can delay growth of the cover crop until the frost prone days have passed. This may mean seeding in early January to ensure minimal growth during January and February when frost may be a concern. As the weather warms in March, cover crops can take off and build biomass without posing a risk to tree health.
Termination strategies
Winter cover crops are generally terminated nearing the last rainfall events so they do not compete with trees for irrigation water. Termination strategies vary based on type of cover crop and availability of equipment. Cover crops can be terminated by mowing, tillage/disking, grazing, or simply allowing them to dry up if they are low growing. Leaving cover crop residue on the surface protects the soil from wind erosion, acts as a natural mulch to suppress weed seedlings, and releases nutrients to the soil as it decomposes. The downside to leaving residue on the surface is the retention of moisture which could provide habitat for slugs and snails. Incorporating cover crop residue immediately after termination speeds up the decomposition time, increasing nutrient release into the soil. This should only be considered in young or=chards where root damage would not occur due to incorporation. This, however, requires the right equipment and relatively flat terrain, which is not representative of most California avocado operations. Grazing is an effective termination strategy to remove high biomass cover crops. However, it is important to consider GAP and NOP food safety regulations by ensuring animals are not in the orchard within 90 days of harvest.
Triticale and Lamb Hass
- Author: Ben Faber
The avocado lace bug (Pseudacysta perseae, family Tingidae) occurs in the Caribbean, French Guyana, Mexico, and southeastern United States. As of 2006, in California it occurs only in San Diego County. Also known as the camphor lace bug, this pest feeds on certain plants in the family Lauraceae. Hosts are the avocado fruit tree (Persea americana), other Persea species such as red bay (P. borbonia), and camphor tree (Cinnamomum camphora), which is grown as a landscape ornamental and commercially for its aromatic extracts.
Recently, Dr. Mark Hoddle from UC Riverside presented an update on the bug and its potential for spread in California. Hoddle is a biocontrol specialist who has done extensive work on this pest, as well as many other pests that afflict plants in this state. Here him:
And while you are at, you might check out the numerous other videos on file at UC IPM's "Ask The Ag Experts" website.
photo: Avocado lace bug, Pseudacysta perseae, adults, nymphs, and eggs under black excrement.
Photo by David Rosen.