- Author: Karey Windbiel-Rojas
The UC Statewide Integrated Pest Management Program's website contains many useful features to help identify pests and problems in the garden and home. One such feature is the Weed Gallery, which contains hundreds of images and management tips for more than 150 common weeds found in California.
If you don't know what weed you are dealing with, the gallery will help you identify the plant using visual characteristics. First, narrow your search by selecting the weed category—broadleaf, grass, sedge, or aquatic plant (Figure 1). You will then see a collection of photos in that category.
Select the appropriate plant characteristic (Figure 2) to see another sub-menu of weeds that exhibit the traits of your weed. Scrolling over a thumbnail image on this sub-menu will bring up several photos of the weed—as a seedling, as a mature plant, its flower, and its seeds—to further aid in identification (Figure 3).
Once you think you've identified the weed, click on the link of the weed's name, which will take you to a photo gallery page where you can read about the weed's habitat, growth characteristics, and life stages (Figure 4). For many weeds, there is a link to a Pest Note that provides information about management, both chemical and nonchemical. In addition, each page in the gallery links to the Calflora website to show where the weed grows in California.
If you think you know the name of your weed, the gallery allows you to quickly access photos using common or scientific names to confirm identification. Just use the “List of All Weeds” link from the main weed gallery page.
The gallery contains other features as well:
- Want to know more about plants and their parts? Illustrated tutorials distinguish among broadleaf, grass, and sedge plants and define plant parts used in characterizing certain plant species.
- Need to identify common weeds found in lawns or turf? The broadleaf and grass categories link to a dichotomous key, where users can pinpoint common turf (and landscape) weeds.
- Didn't find your weed? See the weed identification tool under “More information” to search the UC Weed Research & Information Center (WRIC) technical weed key.
You can access the weed gallery page from the left-hand column on many pages on the UC IPM website or from the various weed-related pages within the website. To access the weed gallery directly, visit http://ipm.ucanr.edu/PMG/weeds_intro.html.
- 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.
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.
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
Conditions are right for weeds
Early rain combined with unseasonable heat this week makes for ideal conditions for weeds,well, everywhere!Get ahead of the menace with these UC guides to weed control. For gardeners growers, range managers, just about everyone!
Act quickly-these prices end February25!
This encyclopedic yet easy-to-use2-volume set covers 262 individual entries, including a full description of 451 species and another 361 plants compared as similar species, representing 63 plant families. Includes a CD of every photograph in the book--perfect for your presentation slide deck.
Showprice:$40.00-Save over 35%!
- Author: Gale Perez
Our friend Lynn Sosnoskie (at Cornell University) shared the following announcement with us:
A free (downloadable) resource
Manage Weeds on Your Farm – A Guide to Ecological Strategies
“I am most pleased to share the good news that our long-awaited SARE-sponsored book “Manage Weeds on Your Farm – A Guide to Ecological Strategies” by the late Chuck Mohler, John Teasdale, and me has now been published online and is freely available for download from the SARE website link below. This is a great resource that took Chuck and I (and many student assistants) numerous years to complete. The coming onboard of John Teasdale as a co-author during the last two years was enormously helpful especially given Chuck's failing eyesight and his untimely passing.”--Toni DiTommaso, Professor and Chair, School of Integrative Plant Science Soil and Crop Sciences Section, Cornell University
ABOUT THE AUTHORS
PART I CONCEPTS OF ECOLOGICAL WEED MANAGEMENT
CHAPTER 1 INTRODUCTION
- Purpose and Philosophy
- How to Use This Book
CHAPTER 2 HOW TO THINK ABOUT WEEDS
- What is a Weed?
- The Origins of Weeds
- Weed Populations are Dynamic
- Weed Density Affects Weed Death and Reproduction
- Vegetative Propagation of Perennial Weeds
- Seed Weight
- Seed Germination: Why Tillage Prompts Germination
- Season of Weed Emergence
- Seed Longevity
- Depth of Seedling Emergence from the Soil
- Growth and Competition for Light
- Photosynthetic Pathway
- Sensitivity to Frost
- Drought Tolerance
- Nutrient Use
- Response to Soil Physical Conditions
- Response to Shade
- The Timing of Reproduction
- The Magnitude of Reproduction
- Natural Enemies
CHAPTER 3 CULTURAL WEED MANAGEMENT
- Many Little Hammers
- Crop Rotation and Weed Management
- Crop Competitiveness
- Cover Crops
- Organic Mulch
- Continuous No-Till Vegetable Production Using Organic Mulches
- Synthetic Mulch
- Weed Management During Transition to Organic Production
- Natural Product Herbicides
- Livestock for Weed Management
- Preventive Weed Management
- Preventing the Arrival of New Weed Species
CHAPTER 4 MECHANICAL AND OTHER PHYSICAL WEED MANAGEMENT METHODS
- Essential Concepts of Mechanical Weed Management
- Types of Tillage and Their Effects on Weeds
- Using Tillage Against Perennial Weeds
- Tillage Effects on Weed Seedling Density
- Ridge Tillage
- Tilled Fallow
- Stale Seedbed
- Principles of Mechanical Weeding
- Cultivators and Cultivating Tools
- Other Physical Weed Control Devices
- Cultivator Guidance Systems
- Matching the Implement to the Task
- Hoeing Weeds
- Cultivation and Tillage in the Dark
- Soil Tilth and Cultivation
- Energy Use in Physical and Chemical Weed Management
CHAPTER 5 PROFILES OF FARMS WITH INNOVATIVE WEED MANAGEMENT PRACTICES
- The Martens, Penn Yan, N.Y.
- Paul Mugge, Sutherland, Iowa
- Eric and Anne Nordell, Trout Run, Penn.
- Scott Park, Meridian, Calif.
- Carl Pepper, O'Donnell, Texas
PART II MAJOR AGRICULTURAL WEEDS OF THE UNITED STATES AND CANADA
- How the Species Chapters Were Developed How to Find Ecological Information and Develop a Management Plan for Species not Covered in this Book
WEED CHARACTERISTICS SUMMARY TABLES
GRASS WEEDS AND THEIR RELATIVES
- Annual bluegrass
- Downy brome
- Fall panicum
- Italian ryegrass
- Large crabgrass
- Purple nutsedge
- Wild garlic
- Wild oat
- Wild-proso millet
- Yellow nutsedge
BROADLEAF WEEDS AND THEIR RELATIVES
- Annual sowthistles
- Canada thistle
- Catchweed bedstraw and false cleavers
- Common chickweed
- Common cocklebur
- Common groundsel
- Common lambsquarters
- Common milkweed
- Common purslane
- Common ragweed
- Common sunflower
- False cleavers (see “catchweed bedstraw and false cleavers”)
- Field pennycress
- Giant ragweed
- Hemp sesbania
- Palmer amaranth
- Perennial sowthistle
- Prickly lettuce
- Prickly sida
- Wild buckwheat
- Wild mustard
- Wild radish
- Yellow woodsorrel
- Author: Rebecca Ozeran
In the 5 years I've been with UCCE, I have received a few recurring weed-related questions. I've certainly had some unique requests, like how to deal with fig trees invading a livestock water pipeline, or whether filaree might be harmful to guinea pigs (it isn't). But often, questions I receive about rangeland or pasture weeds fit under three categories:
- Is this plant toxic to my animals?
- How can I get rid of yellow starthistle?
- What can I plant in my pasture to outcompete all these weeds?
Of course, each question has its own “It depends”-style answer. But today, I want to share the resources I recommend for these Frequently Asked Questions.
Is this plant toxic? (Usually following the question, “What is this plant?”)
- Toxicity varies with plant species, growth stage, part or structure (e.g leaf versus flower) and relative abundance. Toxicity also varies with animal species and size, and what other feed is available. Some plants are toxic at all growth stages and in all parts of the plant (such as oleander) while other plants accumulate toxins at certain times of their growth cycle (such as plants that accumulate nitrate) or affect livestock species differently (such as yellow starthistle).
Fiddleneck, like oleander, accumulates toxins in all plant parts, though the concentration can vary. Fiddleneck seeds and flowers often contain the highest concentrations of alkaloids within a single plant.
- Fortunately, we have an excellent guide that describes common toxic plants and how to reduce risk to your animals: Livestock-Poisoning Plants of California. For plants that aren't listed, you can always contact your local farm advisor for assistance in plant identification and management! If you suspect plants are poisoning your animals, please contact your veterinarian ASAP.
How can I get rid of yellow starthistle?
- While we probably can't eliminate it completely,yellowstarthistle can be managed to reduce its impact on landscapes and livestock. Several usefulresourcesdescribeyellowstarthistle management, and can be freely accessed or downloaded:
- UC IPM Pest Note on Yellow Starthistle, a brief overview of the plant itself and key management strategies
- Yellow Starthistle Management Guide, published through Cal-IPC, probably the most thorough document on yellow starthistle impacts and management tools
- Yellow Starthistle weed report, from Weed Control in Natural Areas in the Western United States, especially handy if you want a concise comparison of management options, or something that is well formatted for printing out
What do I plant to manage pasture weeds?
- Maintaining healthy forage cover is one of the best ways to reduce weed pressure in a grazing or haying area, whether irrigated or not. However, getting good forage established can be more challenging when there are weeds already present. Drought years like this year don't help, either – many deep-rooted broadleaf weeds are doing fine while desirable grasses had a shorter than usual growing season. And, of course, site-specific variations affect what forage plants might be competitive, and what weeds they might have to outcompete.
- Because the answer is more complicated than “buy X seed mix”, I usually refer to the excellent guide, Establishing and Maintaining Irrigated Pasture for Horses. The principles of pasture preparation, including strategies for weed management during pasture establishment, are similar across grazing livestock species. Most of the information in the guide can also apply to dry pastures aside from the specific sections about planning and using irrigation.
Healthy pastures will better outcompete weeds. The species in that pasture will vary across the state. Having sufficient moisture - from rain or irrigation - also impacts weediness!
Now, range and pasture weed questions aren't going to be completely resolved by a single blog post – but I do hope this post is a helpful starting point for anyone who manages rangelands or pastures.
If you have a question that isn't listed in this short FAQ, feel free to reach out! I'm happy to expand this resource. You can comment on this blog, email email@example.com, or message through my program Facebook page.