- (Focus Area) Pest Management
- Author: Drew A Wolter
- Posted by: Gale Perez
Why scout for weeds?
While weeds are present in every orchard, there is variation in the weed species composition and density from orchard to orchard. Scouting for weeds is the basis for a good Integrated Weed Management (IWM) plan. Information gathered from weed scouting allows growers to:
- Evaluate the current year's weed control program
- Adjust control practices for the following year
- Discover weed stands and possible resistance before they spread throughout the orchard
- Select the best control option for species of concern, such as:
- Choosing appropriate management tactics for species present
- Identifying areas for possible spot treatments
- Selecting best cultivation method for weed stage
- Altering cultural practices to target weed life cycles
Post-harvest scouting offers an opportunity to evaluate the current year's orchard floor management plan, allowing you to see what weed species escaped management, where they are, and how severe the infestation may be. These are all valuable pieces of information when designing a management program to meet the specific needs of the orchard from year to year.
Keys to scouting
Most weed species are much more challenging to manage as they mature. Because of this, post-harvest scouting should start early and be repeated once more before the start of the season in order to catch weeds when they are young. Herbicide applications targeting mature weeds are often minimally effective, resulting in a less successful program and increased management costs. Three keys for successful scouting:
- Record weed infestations and use a map/GPS to show areas of escaped weeds. Below are links to UC IPM weed scouting templates for several common tree crops in California. Each template provides a chart with the most common weeds already listed and a designated area for mapping orchard weeds found while scouting.
- Accurately identifying weed species is crucial for effective management because herbicide recommendations, mechanical, and cultural control strategies vary depending on the species. While some species can look similar, they may have drastically different management requirements. For help identifying some of the weeds you may find visit: UC IPM- Weed Identification, the multi-state Weed ID tool, or other online or commercial weed ID guides
- Look out for different weeds in different management zones. A good place to start is by checking in the tree rows to evaluate the effectiveness of any previous herbicide applications. Check the ground cover in the row middles for any seedlings of annual and perennial weeds. Check orchard borders and at the ends of rows where new species are more likely to be initially introduced.
With the growing number of herbicide-resistant weeds in California orchards, control of escaped weeds can considerably reduce the long-term cost of an annual orchard floor management program. For example, spot treating two acres of glyphosate-resistant palmer amaranth with a tank mix of glufosinate and paraquat is much more affordable than trying to control it over an entire 50-acre block. There are currently thirty confirmed herbicide resistant species in California; for more information regarding the status of herbicide resistance in California visit the UC Weed Science post from January 2019, titled The Current Status of Herbicide Resistance in California. Remember to scout this winter so you can spot treat, rather than having an orchard full of herbicide-resistant weeds in the future.
- Posted by: Gale Perez
From the Western IPM Center November 2019 newsletter...
Looking for Answers as Kochia Rolls Across the West
“It's salt tolerant, heat tolerant, cold tolerant,” said Kent Davis, a crop consultant with Crop Quest in Colorado. “I want to kill the damn stuff, there's no question about it, but you have to admire it at the same time.”
Davis spoke at a recent meeting of a kochia work group, funded by the Western IPM Center, where some 50 researchers, growers, herbicide industry representatives and graduate students focused on all the challenges in managing kochia. In addition to its hardiness, as a tumbleweed, kochia spreads quickly and exchanges genetic material with other strains readily. It's also developed resistance to multiple herbicides and chemical pesticide manufactures struggle to, as one company representative put it, “stay two modes of action ahead of kochia.”
The work group meeting in Denver took a high-level look at the state of kochia control and the research steps needed to continue to manage it.
“We want to look broadly at the biology and ecology of kochia, at integrated management and herbicide resistance, and we're including sessions on education and social science since that will have to be part of the solution,” explained Todd Gaines, a weed scientist at Colorado State University and project director of the work group.
The value of the work group quickly became obvious as researchers from different universities from Oregon to Texas talked. Noting that they all do resistance studies slightly differently, they agreed that developing a unified protocol would be useful, and they identified priorities for future research.
“Some of this is low-hanging fruit,” Gaines said. “A common protocol is a good example of that. We also want to see who is doing what and see if there are some natural divisions of labor we can identify going forward.”
Some researchers are examining the seed bank, looking for ways to keep kochia from germinating, or forcing its germination to give growers a good window to control it with herbicides. Kochia is a quick-germinating weed, with 95 percent of its seeds germinating within two years. That's encouraging for techniques based on seed-bank reductions, but it has a caveat.
Others are looking at genetic solutions for managing kochia, which recently has had its genome mapped. Philip Westra, a weed scientist at Colorado State University, mused about looking for genetic modifications to the plant's abscission layer, which allows the weed to break off and blow around – in effect untumbling the tumbleweed.
Other researchers surveyed growers to see how they were thinking about and managing kochia, and some of those statistics weren't encouraging. Half the responding growers thought they had herbicide-resistant kochia in their fields. Two-thirds of the respondents said they were doing a good job managing kochia and resistance, but only 30 percent thought their neighbors were doing a good job.
Other data were more encouraging. Making a presentation on integrated management of kochia, Nevin Lawrence at the University of Nebraska-Scottsbluff, showed that while worst-case kochia infestations could deposit 12,300 seeds in a square meter, a combination of tactics to control kochia, including tillage, cover crops, and targeted crop and herbicide rotations, brought that number down to 352 seeds per square meter.
“It won't be one answer,” he said. “It's going to take an integrated approach.”
The research priorities established by the work group reflect that. They are:
- Basic seed biology – coordinated, multi-state, long term seed bank dynamics; improved seed storage for reference lines; stimulating synchronized germination
- Standard resistance testing protocol and rating system, standard reference lines available for all to use
- Integrated Weed Management modeling for a kochia management decision-support tool
- Coordinated communication material; survey of current practices for scope of problem and barriers; initial area wide management groups
Kochia as a Solution?
Not everyone at the meeting had it in for kochia. Kevin Dorn, a researcher working on sugar beets for the U.S. Department of Agriculture's Agricultural Research Service, sees kochia as a potential future solution, not just a problem.
“Sugar beets are very disease-sensitive,” he explained. “You'll see fields of sugar beets stunted from disease with healthy kochia growing right next to it. Because sugar beets and kochia are in the same family genetically, it may be possible to take some of the traits that make kochia such a difficult weed to manage and use them to improve the agricultural crop. That's not going to happen soon, but because the genome has been mapped, it's something we can start to look at.”
A salt-tolerant, heat-tolerant, cold-tolerant and disease-tolerant weed is a big problem, however, those same attributes in a sugar beet would be sweet indeed.
- Author: Lauren Snowden
It may seem odd to see seventy-five people at a hotel conference center learning about insects and rats on vegetables, but not if you are a UC Master Gardener. The UC Statewide Integrated Pest Management Program (UC IPM) in partnership with the UC Master Gardener Program just wrapped up the Vegetable Pests and Solutions train-the-trainer series. More than 340 UC Master Gardener volunteers from across the state took part in the regional trainings offered in Fresno, Orange, Placer, San Luis Obispo and Sonoma counties.
The advanced UC IPM training offered a hands-on, train-the-trainer experience that increased participants' knowledge of insect pests of vegetables, vegetable plant diseases and disorders, and vertebrate pests of gardens and homes. One of the highlights of the training was Human-Wildlife Interaction Advisor, Niamh Quinn, showing a taxidermy collection of vertebrate pests at the Orange and San Luis Obispo County workshops. Being able to handle and observe the different markings, colors and claws on certain animals makes future identification easier as participants learned the signs to look for when identifying vertebrate pest damage in the vegetable garden.
UC Master Gardener volunteers were lead through exercises that mimic questions commonly received from the public. Some of the questions had a photo, others just a sparse description that volunteers worked together to solve using online IPM resources and materials provided at the training. The exercises were designed to challenge and expose the learner to different types of scenarios and tools they can use in the future.
Outreach and Education
The UC Master Gardener Program's mission is to extend research-based information, by attending advanced trainings such as this, volunteers are even more prepared to contribute to the program's mission. With exposure and practice using new resources and materials training attendees have the tools and knowledge needed to educate the public on vegetable pests and solutions including scripted PowerPoints, activities, handouts, and vegetable pest identification card sets. One attendee reported “As a first year UC Master Gardener, this training helped me become more comfortable and more confident researching answers for pest management questions.”
At the conclusion of the training volunteers convened with their fellow county volunteers to talk about their plans to take new found knowledge back into their communities. Some of the great ideas generated were:
- offer seasonal pest problems workshops
- include a “Need Help Solving Pest Problems?” flier for all events
- add IPM tips to newsletters and social media
- integrate IPM into presentations as appropriate or relevant to topic
- add signage for damaged or diseased plants with IPM solutions in demonstration gardens
- share IPM toolkit at farmers markets and demo garden events
How We are Making a Difference
One portion of the agenda was focused on how the UC Master Gardener community is making a difference. With 6,000+ volunteers serving more than 517,000 Californians per year the impact of the UC Master Gardener volunteer effort is truly amazing. Through statewide program evaluation efforts the impact in sustainable landscaping, food gardening and community well-being is now being analyzed and reported in the programs annual report. Volunteers can see the impact they are having statewide and be proud of being part of a group that social changes they are seeing in their local communities.
As active volunteers and life-long learners UC Master Gardeners are a powerful educational tool and inspiration for others not only in the garden but in the volunteer community. Statewide educational offerings like UC IPM's train-the-trainer series help hone the diagnostics skills while building confidence in the subject matter.
The next statewide training opportunity for UC Master Gardener volunteers will be the 2020 UC Master Gardener Conference, Sept. 28 –Oct. 2, 2020 at the Granlibakken, Tahoe. The conference is the beginning planning stages and taking speaker and topic suggestions, click here to suggest a speaker or topic.
- Author: Rebecca Ozeran
Many factors make weed management on federal public lands an interesting challenge.
In September I was invited to join one of the Sierra National Forest Rangeland Management Specialists to explore a medusahead infestation in one of the grazing allotments she manages. The infested meadow used to be a homestead, though the only obvious reminder is the cluster of still-productive apple trees in the middle of an otherwise grass-dominated site. Pines and other conifers border the meadow, and a forest road divides the meadow into two parts. The portion uphill of the road is steeper and has more trees interspersed with the herbaceous vegetation, while the downhill portion is a more expansive, gentler sloping meadow. Due to the elevation, a variety of broadleaved (forb) species were still green, but the medusahead and other annual grasses were long since brown. Springs throughout the area supported green forbs, rushes and sedges.
During the site visit, the specialist wanted to brainstorm ideas for how to reduce the medusahead population. The primary management tools being considered are targeted grazing and prescribed burning. Since the meadow is already grazed, one of the big hurdles to targeted grazing – finding animals to do the job – is reduced. However, concentrating the animals in the area to graze the medusahead more intensively than normal will require additional infrastructure. We discussed the potential for temporary or permanent cross-fencing, to keep an appropriate number of cows in the target area for a specified time frame. For reference, during the 2017 grazing season there were about 66 acres of forest, meadows, and everything in between for each cow in Sierra National forest grazing allotments. By contrast, this meadow is less than 50 acres, and the goal would be to have enough cattle confined to the meadow for a given grazing period so that the cows actually eat the medusahead before it produces seed.
We also discussed the variability of the vegetation in the meadow – from the apple “orchard”, to miniature wetlands, to annual grassland types. Without any additional incentives, the cattle are likely to stay close to the areas with the most resources: the existing water trough, the shade of the apple trees, and the lushest patches of forage. Strategic mineral or protein supplementation, or a secondary water development could attract the cattle to the densest patches of medusahead and away from the springs where no medusahead is growing.
Grazing makes the most sense as a control method on the downhill, larger meadow area. However, the specialist noted that the uphill, smaller meadow area could be a good candidate for a prescribed burn. On the uphill patch, there are more trees and less forage; it would be harder to fence due to the topography (and thus harder to keep the cows on the medusahead); there isn't a developed livestock watering source uphill of the road; and the Forest Service already has plans to burn the neighboring areas this fall and winter. In essence, grazing would be hard to implement, but the protective nature of the neighboring burns would mean a prescribed fire could be feasible under the right conditions.
Before any of our brainstormed ideas can be implemented the specialist must do several things. First, she needs to consult with the cattle owner who grazes the area, to see if they are willing and able to install the necessary fencing. Forest Service grazing allotment permittees are expected to maintain the grazing infrastructure on the allotments they graze, so the rancher is on the hook for installing a new fence if they decide to move forward with the targeted grazing plan. This is a huge benefit to the Forest Service – the maintenance and infrastructure that permitted ranchers provide on grazing allotments would otherwise cost the Forest Service thousands of dollars and many employee hours per allotment per year.
Even if the rancher is on board with the project, additional Forest Service requirements make projects slow to implement. National Forests are multi-use landscapes, which means that there are many potential uses which all must be considered when implementing a project. Uses of Sierra National Forest include recreation, grazing, and wildlife habitat. As such, all proposed projects must undergo environmental evaluation to ensure any environmental concerns are identified and mitigated or resolved. Even for a project like the potential targeted grazing – which uses a land management tool that has previously been approved on the meadow, just at a different intensity – the site will have to be evaluated. If all goes smoothly, the range management specialist hopes to begin with the grazing plan once the allotments open for grazing next year.
As you can imagine, weed control on federal public lands can be quite a challenge – even if a project is approved, it may be months after the original proposal, and some management tools may not even be options to begin with if the public opposes their use. I hope to be able to share a success story about this plan being implemented by this time next year, and will follow with observations of the results as available.
- Author: Kathy Keatley Garvey
And UC Davis plant nematologist Shahid Siddique, formerly with the University of Bonn, is at the heart of it.
He led a 10-member international team in discovering the role of a plant's endodermal barrier system in defending against plant-parasitic nematodes.The Plant Journal published the research, Root Endodermal Barrier System Contributes to Defence against Plant‐Parasitic Cyst and Root-Knot Nematodes, in its July 19th edition.
Fast forward to October.
Research Highlight Editor Lysa Maron chose the work as the "research highlight" in her Oct. 14th article, “Breaking or Sneaking into the Fortress: the Root Endodermis is a Defence Wall Against Nematode Infection.” The journal also showcased the team's nematode image on the cover.
What's the significance of the research?
“We discovered that the integrity of the endodermis—a specialized cell layer that surrounds the vascular system and helps regulate the flow of water, ions and minerals--is important to restrict nematode infection,” said Siddique, an assistant professor in the UC Davis Department of Nematology who joined the faculty in March after serving several years at the University of Bonn.
“We found that having defects in endodermis make it easier for parasites to reach the vascular cylinder and establish their feeding site. Although, this finding is a result of basic research, it opens new avenues to for breeding resistance against cyst nematodes in crops.”
Maron noted that “Roots are a truly amazing plant structure: they conquer the underground, form complex structures that anchor the plant, let water and nutrients in, but must not dry out. Roots store energy, send signals to the aboveground parts of the plant and to neighbors, and defend the plant against soil-borne pathogens. Within the root, the endodermis is the barrier that separates the inner vasculature from the outer cortex. If the root is a fortress, the endodermis is the gated wall. Cell wall reinforcements such as the casparian strip (CS), lignin deposition, and suberin seal the apoplast of the endodermis throughout different parts of the root. These reinforcements allow the diffusion of water and nutrients to and from the vascular tissue while blocking its penetration by pathogens such as bacteria and fungi (Enstone et al., 2002).”
“But roots also face pathogens of a different kind: root-infecting, sedentary endoparasites such as cyst nematodes (CNs) and root-knot nematodes (RKNs),” Maron wrote. “These pathogens infect a variety of important crops and cause significant yield losses (Savary et al., 2019).”
Maron quoted Siddique: “According to Siddique, investigating root traits that affect plant-nematode interactions is important for finding new strategies for plant protection. Screening for natural variation in suberin- and lignin-related traits might help identify and develop stronger fortresses, i.e., plants with enhanced resilience against pathogens, drought, and nutrient deficiency.”
Siddique collaborated with scientists from Germany, Switzerland and Poland: Julia Holbein, Rochus Franke, Lukas Schreiber and Florian M. W. Grundler of the University of Bonn; Peter Marhavy, Satosha Fujita, and Niko Geldner of the University of Lasuanne, Switzerland; and Miroslawa Górecka and Miroslaw Sobeczak of the Warsaw University of Life Sciences, Poland.
“Plant-parasitic nematodes are among the most destructive plant pathogens, causing agricultural losses amounting to $80 billion annually in the United States,” said Siddique in an earlier news story. “They invade the roots of almond, tomato, beets, potato or soybeans and migrate through different tissues to reach the central part—the vascular cylinder--of the root where they induce permanent feeding sites.”
“These feeding sites are full of sugars and amino acids and provide the parasite all the nutrients they need,” Siddique explained. “A specialized cell layer called the endodermis surrounds the vascular system and helps regulates the flow of water, ions and minerals into and out of it. However, the role of endodermis in protecting the vascular system against invaders such as nematodes had remained unknown.
The German Research Foundation funded the research.