- Author: Ben Faber
Black Fig Fly (Diptera: Lonchaeidae: Silba adipata)
Invasive Fig Pest Recently Discovered in Southern California
Click Here to Download the "Pest Alert" PDF
Overview
Fig growers need to be aware of the black fig fly (BFF), an invasive insect that was recently discovered infesting figs in multiple counties in southern California (see map below). The BFF has been reported in the following counties: Los Angeles, Orange, Riverside, Santa Barbara, San Bernardino, San Diego and Ventura. Movement of figs from these counties is strongly discouraged, since it may lead to additional spread of BFF to other areas of the state. University of California Cooperative Extension personnel are currently working with the California Department of Food and Agriculture to further delineate populations, as well as develop improved monitoring and management strategies.
Please Do Not Move Figs
California figs are primarily grown in the Central Valley between Merced and Fresno, with many smaller orchards spread along the coast and in southern California. Movement of figs from the infested counties is not recommended, as it may lead to additional artificial spread of BFF to other areas of California.
Reporting the Pest
If you find infested fruit or suspect that BFF may be attacking fruits in your orchard or yard, please contact your local UCCE Farm Advisor and County Agricultural Commissioner. You can also report this pest to CDFA's Pest Hotline: 1-800-491-1899 (https://www.cdfa.ca.gov/plant/reportapest/).
Adult female black fig fly depositing eggs into the fig ostiole (photo: H. Wilson)
Damage to fig from black fig fly larva (Photo: H. Wilson)
While approximately 90% of California fig production is in the Central Valley, infestations have so far been limited to Southern California
- Author: Mindy Robinson
Coming to citrus orchards?
An ongoing study in hazelnut orchards offers possible electric weed control (EWC) solutions for other tree nut orchards, especially in light of increasing herbicide resistance.
Marcelo Moretti, Assistant Professor at Oregon State University, conducted two studies in 2021 utilizing EWC to manage Italian ryegrass in hazelnut orchards. One study focused on the necessary speed of operation to provide effective weed management. The second, multi-year study focuses on crop safety when using EWC.
Because hazelnuts are harvested from the ground, they are grown conventionally with mostly no cover crops and no tillage. Mowing suppresses the tops of weed plants but requires too many passes to be effective.
For the herbicides used in hazelnuts, growers are seeing resistance to all of the post-emergent herbicides such as paraquat and glufosinate, Moretti says. Thus, a non-chemical weed control alternative is needed.
“The end goal is to control or eliminate (weed) seed production in order to have the benefits of rye grass as a cover crop but be able to kill it when not needed,” Moretti says.
With today's growing herbicide resistance, commercial developers such as Zasso, RootWave, and Crop.Zone have developed EWC units focused on meeting the needs of different agricultural users.
HOW EWC WORKS
EWC kills weeds with thermal energy. A high-voltage electrode touches the foliage of the plant, allowing an electric current to pass through the plant; electric resistance in the plant converts the electrical energy to heat, killing the plant. The higher the plant's conductivity, the less energy it takes to kill the plant.
An EWC unit is typically tractor-mounted, and the unit's generator is connected to a PTO (Power Take Off). The generator is coupled to a transformer that increases the voltage. A module controller connects to the electrodes that are contained in sets of electrical fingers, which provide applicator contact to the plants and the soil. The applicators vary in shape and size, which is dictated by the size of the generator. A 30 kVA generator can treat about four feet at a time.
Along with equipment setup, the target plant and soil conditions play a role in the efficacy of the operation. Plant factors such as morphology, stage of development, water content, and plant density all affect EWC efficacy. Younger, herbaceous plants with high water content and particular root systems are more susceptible to EWC applications.
Soil factors include impedance, mineral composition, texture, moisture, temperature, and porosity. EWC is more effective in soils that have less conductivity, which forces the electricity to stay in the plants longer, creating more thermal energy. Optimum soils with low conductivity are lighter, sandy, dry, and warm.
STUDY RESULTS
Moretti's study on the necessary speed of operation for EWC using a Zasso unit shows that 9,000 volts at 2 mph efficiently kills Italian ryegrass. When soil conditions are wetter, the unit must be run at 5,000 volts to minimize the risks of damage to the EWC unit or the tractor. Although the 5,000-volt setup (at 1 mph) is less efficient, it does kill ryegrass.
Moretti's multi-year study on crop safety looks at variables such as plant variety, electric rates, and application — with and without suckers. The study will monitor tree growth, photosynthesis rate, and yield. Based on the 2021 results, EWC has not adversely affected crop safety.
Although not a part of the study, Moretti observed that yellow nutsedge, Canada thistle, field bindweed, and horsetail were all sensitive to EWC.
As the study progresses, cost factors also will be evaluated.
As expected, the most significant limitation of EWC is the potential for causing fires. In Oregon, EWC is not ideal when it is too dry (usually after July) or too wet.
EWC provides effective weed control at 2 mph, is initially safe to hazelnuts, and is safe to humans. It is compatible with existing production systems, as it does not damage irrigation lines.
The economics are to be determined but initially show to be about $50 per acre to implement — comparable to conventional herbicide application — after the initial equipment investment (Moretti purchased a Zasso unit for $50,000 in 2020 for this study). The benefits to the environment are that it leaves no chemical residue and does not require soil tillage.
From Growing Produce
And see what those folks at UC Davis are doing with electrical weed control - EWC
A Zasso electric weed control unit mounted on a tractor demonstrates its capabilities.
Photo by Marcelo Moretti, Oregon State University
- Author: Ben Faber
There's a lot of new trees going into the ground, both citrus and avocado. Especially avocados are getting tucked into lots of little corners. There's money to be made and maybe there will be in the future. One of the many issues of planting trees is you want to make sure that ground has been surveyed/evaluated/tested for various problems like salts and pH before planting. It's always easier to correct these issues before trees go in the ground. Once there, it can be a wild experience trying to figure out the problem, and by the time a plan of action has been worked out, trees are dead or stressed and it can be difficult to correct. Read a bit more about this HERE
However, the reason for this blog is really to point out that attention needs to be paid when planting trees. They cant be planted too deep. Burying the stem below the level at which they come from the nursery, can lead to serious problems like tree death. The most physiologically active portion of the root system is the crown, the point at which the roots start spreading out from the stem. Bury that area lower than it had been growing in the nursery, and it causes asphyxiation.
Planting can be a manic process of getting trees out and then moving across the landscape to get them into the ground and watered and adjusted to their new environment. It needs to be methodical and if the hole is too big and too much loose soil, or a planting mix is incorporated that eventually decomposes and allows the tree to sink below grade over time, the stem will get buried. Planting on mounds and berms can add to the problem when the planting site gradually settles over time and buries the stem. So many ways it can happen. The rule of thumb is if planting right doesn't work, it's better to plant high and allow time to settle the tree.
Following is a sequence arriving at a buried stem. Slow down, you move too fast, you want the planting to last.
It's tough planting on rocky hillsides
Something is not going well up there, one or two are dying
Tree is not doing well, and whitewash isn't helping much at this point
Where are the roots, just coarse ones? Notice the dirty paper trunk guard that has been buried
No small roots, this stem was buried too deep. Dieback in the root, means dieback in the canopy
- Author: Nicki Anderson
Community Education Specialist
A Fresh Soil Health Resource
In 2015, a group of graduate students at the University of California, Davis attended a hearing on California's Healthy Soils Initiative. They witnessed firsthand the power of storytelling to captivate an audience, as well as the challenges of communicating uncertainty and nuance regarding the dynamic nature of soil.
They started a seminar to discuss and develop science communication, which evolved into a campaign to raise awareness about the value and importance of soil, which caught the attention of the Natural Resource Conservation Service, and ultimately led to a collaboration to produce educational resources (links below).
Their mission is:
- To inspire the next generation of soil explorers for the benefit of all
- To educate that soils are living bodies that harbor a diversity of life, and support and sustain life as we know it
- To empower young power with solutions to some of our greatest global challenges; solutions that lie right beneath our feet!
After years of work, the Soil Life website has officially launched.
The site includes
1) An interactive, graphics-based introduction to soil science;
2) A media hub of soils-related content, and
3) Clear, actionable ways for people to 'get involved' protecting and promoting soils in their everyday lives.
They have also launched the first video in a 6-part series highlighting the connection between soil and life.
Check out their website,
Watch "The Story of Soil and Food," and
Share with your networks (especially the educators and young people in your lives!)
The website and videos were produced under a UC Davis/USDA-NRCS collaborative project and are part of a national campaign to raise awareness about the value and importance of soil.
- Author: Ben Faber
Topics in Subtropics Newsletter Volume 23 Spring 22
Topics in this issue:
- Phytophthora disease associated with citrus in California
- Is it root rot? Or? The 12 signs of ARR
- New avocado irrigation study
- GEM vs Hass?
- Area-Wide Treatment of ACP
And there are past Newsletters here and
there's a site where you can subscribe
for alerts to future Newsletters.
You can also subscribe to this blog - coming a few times a week
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