- Author: Annie Sicotte, UCCE Master Gardener
Flowers and veggies lingered in my garden this year, encouraged by the mild autumn weather. Then came the holidays, followed by rain. So much for Fall garden tasks and cleanup chores. Between rainstorms in January, I walked around the garden amazed at how quickly the ground turned from golden fall leaves to a green carpet. As the summer garden died back, weeds took advantage of less competition and filled in the open spaces. They grew from seeds that blew in, were dropped by birds, or were stored in the soil “seed bank' from previous plants that went to seed – just waiting for the right conditions to germinate. Constantly moist soil and cool weather allow seedlings to get their roots established before the soil dries out.
Those beds of weeds are often ignored until Spring weather urges us to get our summer garden started. By then, the weeds are lush and well-rooted. “Weeding” becomes an unpleasant, daunting task if we wait.
Since weeds rob plants of nutrients and provide habitat for unwanted pests, it is important to control them early while they are still small. Although pulling weeds seems like a no-brainer, there is a definite way to do it efficiently. Grab a knee pad, hand hoe, Hori-Hori or trowel, and a big bucket. Kneel at the open edge of a bed and work on the weeds closest to you. Gently pull the largest weeds, lifting the root with a Hori-Hori or trowel. Next, with your fingers, pinch the base of an individual plant and “pluck” the weed out. This loosens the soil around it. making the next plant easier to pull. Gently shake the soil off the roots back into the bed before putting the weed in your bucket. Now, give the cleared area a shallow scuffle with the hand hoe to dislodge small seedlings. Don't dig weeds with a spade or disturb the soil deeper than an inch. This is hard on the soil structure and brings more weed seeds to the surface. Don't get anxious. If you try to grab and pull large handfuls, it only breaks off the leafy tops, which soon regrow from the leftover roots. It's better to do a smaller area thoroughly. Finally, add a 1” layer of weed free compost to the cleared area. This prevents light from germinating new seedlings.
Pulling weeds will give you a chance to appreciate the abundance of slugs and snails as well! It always catches me off guard to see how early the eggs begin to hatch. These voracious tiny babies are everywhere I look. Weeds, as it turns out, are a perfect hiding place to avoid predators. Tucked under the flat rosette of Shepherd's Purse or in the axis of an Asparagus leaf, slugs can eat and grow and not be found. Removing the weeds will greatly reduce their hiding places, as will removing last season's straw mulch and keeping the grass short around the garden beds… But slimy things are persistent in coastal gardens.
The undersides of wilted summer foliage keep snails happy and dry until tastier foliage emerges. They do serve a function, of course. Slowly, they help the decomposition of plant material. Summer plants that have been left to rot give slugs and snails an easy dinner. As I clean the debris and cut back the plants, I have found tiny little snails by the hundreds this year. Cleaning the beds reduces snails, but it also redirects them to the fresh new growth of healthy plants. Although I would love to just leave them for natural predators, there aren't enough birds, snakes, opossums, or other critters to make a dent in this year's bumper crop of mollusks.
There are no sure-fire exterminators for slugs and snails in the home garden. Environmentally concerned gardeners use Iron Phosphate baits like Sluggo with some success. But even the heavy-duty snail baits- the ones that contain Metaldehyde or Carbaryl (that also harms worms, reptiles, birds and some mammals) - only work on the snails that come in contact with the chemical. Many of the small hatchlings emerge and head for a sheltered place above the ground. You'll find them hiding in the tender tops of plants, under the lips of flowerpots, or behind shrub foliage where their ‘foot' never touches the ground. In the cool, damp air of night, they glide from their perch to devour prized plants – which seem to be their favorites. Controlling them becomes a bit more problematic and requires a combination of approaches.
I hesitate to share that hunting slimy slugs and snails has become a bit of a questionably sane, definitely weird obsession for me. You won't find me excited by a dish of beer with a few drunken snails in it. Instead, I clean, prune, plot, bait, consider the possibility of becoming an Escargot farmer, and then become the Human Predator. (That's right - it's my Super- Power. ) To tackle the problem, I put on the garb of a crazed gardener - a bright LED headlamp, rubber gloves, a container of soapy water - and head into the night garden to make my rounds. As I examine each plant, turning over leaves to check bothsides, I pluck my slow-moving prey and pop it into the container, where it sinks to its demise. It's not a pretty sight. But there are just SO many snails!
As the nights go by and the population dwindles, I marvel at the impact I can have on a single population of slugs and snails. Yes, that's right, “a single population” because there will be more eggs hatching. A single snail can lay 6 batches of eggs in a year with up to 80 eggs each. That's 480 eggs for every snail! It's never-ending. But I'm doing my part.
So, I encourage you to get a head start on the weeding and garden cleanup this year. Keep that cool fashion-statement headlamp handy, and just ignore the neighbors' comments about your new nighttime gardening chore. For what it's worth, I can vouch for your sanity.
For additional information about Integrated Pest Management (IPM), including weeds and mollusks, Check out the University of California website https://ipm.ucanr.edu/PMG/menu.homegarden.html?src=302-www&fr=3723
For help identifying and controlling weeds, https://ipm.ucanr.edu/PMG/weeds_intro.html
For more on slugs and snails, https://ipm.ucanr.edu/PMG/PESTNOTES/pn7427.html
All photos are courtesy of the author, Annie Sicotte, and are used with permission.
- Author: Amber Vinchesi-Vahl
- Posted by: Gale Perez
Conventional processing tomato weed management in California often includes pre-plant herbicides (trifluralin and/or s-metolachlor), followed by cultivation, and hand hoeing. Rimsulfuron herbicide can also be used in conventional systems and can be applied either pre or post transplanting. Post-transplant applications of rimsulfuron can selectively remove nightshades if applied when the weeds are very young, no more than 2 true leaves, however, long plant-back restrictions may limit its use. Therefore, the use of hand crews is often needed to remove weeds that emerge in the plant row, where standard cultivation equipment is ineffective.
While both robotic cultivators and finger weeders have been used and evaluated in many vegetable crops, there has been little research evaluating these tools in processing tomatoes and how well they may complement or replace a traditional herbicide program. The main objective of this project was to evaluate crop safety, weed control, time, and costs associated with using mechanical cultivators as part of a conventional weed management program in processing tomatoes. This work is supported by the California Tomato Research Institute, with assistance from grower cooperators.
Methods
This project was conducted in 2020 and 2021 in both Colusa and Merced counties.UCCE Vegetable Crops Advisor, Scott Stoddard, led project efforts in Merced County. Only the Colusa site data will be presented here. The Colusa County field site was located just north of Colusa, CA and the same site was used both years. The field was transplanted to double row tomatoes, on 60” beds. Plot size was 5 beds by 250 ft length, except for Control (Treatment 4) which was 5 beds by 100 ft length to minimize impact. Each treatment was replicated three times. The following treatments were evaluated:
- Rimsulfuron at 2oz/A (grower standard)
- Automated cultivator (1 bed/pass)
- Finger weeder mechanical cultivator (5 beds/pass)
- Control: no in-row cultivation, no post-transplant herbicide.
Results
Weed control results are shown in Figure 5. In 2020, the Robovator and finger weeder did an excellent job of weed control on all plots. In 2020, the Robovator worked very well, providing up to 85% control on average two weeks and four weeks after it was run, and we saw very little crop injury (Figure 6). However in 2021, due to heavy winds in early May, the young tomato plants were not upright, and the robotic weeder had difficulty distinguishing where the stem of the plant was compared to the top of the plant. These plots suffered 11-19% crop loss, which also occurred at the Merced site in 2020 (Figure 7). Despite the crop injury, average weed control was 71% after 2 weeks in 2021 and there was no negative impact on yield. The finger weeder provided 66% on average two weeks post-treatment in 2020. It is worth noting that by plot, the finger weeder provided over 90% control post-treatment in two of the plots. The third plot showed poor control due to heavy bindweed pressure, therefore bringing the average down. The finger weeder also provided excellent control at the Merced site in 2020. In 2021, the finger weeder provided an average of 56% control two weeks after treatment and 66% control four weeks after treatment. The grower standard herbicide treatment of rimsulfuron provided 34% and 44% control on average at two and four weeks after application in 2021, but it is worth noting this field did not have heavy nightshade pressure. Despite the numeric differences between treatments shown in Figure 5, there was no significant difference between the cultivator treatments and the grower standard (rimsulfuron) for weed control in either year, due to high variation in weed pressure between plots, which can be seen from the high standard error values.
In general, hand weeding provided 60-100% control between 2020 and 2021. Hand weeding times and costs were not significantly different between the grower standard (rimsulfuron), finger weeder or robotic weeder treatments in both years and all treatments significantly decreased time and costs compared to the control plots (Table 1). Weed pressure increased in 2021 leading to higher weed counts and longer hand weeding times and associated costs compared to 2020. There were no significant differences in yield between plots in 2020 or 2021.
Summary
Field variation and weed species influenced weed pressure and control, some plots had >300 weeds and others only had 10. There was poor bindweed control from cultivators and hand-weeding crews, which was expected based on the biology of bindweed. Both in-row cultivators provided decent control in 2020. The finger weeder was able to cover five beds per pass and moved quickly through the field compared to the Robovator. All treatments significantly reduced hand weeding costs and time compared to the control in 2020. Despite the crop injury issues with the automated cultivator in 2021, the Robovator plots resulted in the highest % weed control and fastest hand-weeding times.
The finger weeder is gaining popularity in the Sacramento Valley and provides an option for in-row mechanical cultivation without the expense of an automated weeder. Timing is key when using either type of in-row cultivator. The size of the tomato plant and the size of emerging weeds needs to be just right to avoid crop injury while also removing young weeds. The finger weeder provided excellent weed control in Colusa and Merced in 2020, despite poor bindweed control. The automated weeder provided excellent weed control at the Colusa site, but with high crop injury and technological challenges. When working correctly, automated weeders provide accurate and precise weed control, though issues can arise when conditions are not as favorable. In-row mechanical cultivators, like the finger weeder, are more economical, but automated weeders are becoming more prevalent in California for vegetable production systems.
Many thanks to the California Tomato Research Institute, Steve Fennimore, Scott Stoddard, and our grower cooperators for working with us on this project.
Amber Vinchesi-Vahl is the UC Cooperative Extension Vegetable Crops Advisor for Colusa, Sutter and Yuba counties.
This article was published in the March/April 2022 issue of Progressive Crop Consultant.
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- Author: Richard Smith
- Posted by: Gale Perez
Given that the autoweeders mentioned above often leave weeds in the zone right next to the crop plant, we have often discussed the need for machines that can precisely and safely remove weeds right next to the keeper plants. Ideas included the use of precision and pinpoint application of an herbicide or hot oil to the adjacent weeds or removal by lasers. This concept is now a reality because in 2022, there are now machines that employ these ideas. At the 2022 Automated Technology Field Day held in Salinas on June 8th Tensorfield Agriculture (https://tensorfield.ag/) demonstrated their machine that used precision application of hot oil and Carbon Robotics (https://carbonrobotics.com/) demonstrated their machine which used lasers to remove unwanted weeds.
In 2022 Carbon Robotics made the first deliveries of their laser weeder to growers producing onions, carrots and lettuce in the western US. The machine that is in use in the Salinas Valley is three 80-inch beds wide. It is capable of removing weeds from high density plantings such as baby lettuce, spinach and spring mix (Photo 1). The lasers focus energy to the growing point of young weed plants (Photo 2). It is most efficient for the machine to treat young weeds which allows it to spend less time and energy to kill each plant and thereby move more quickly through the field. One of the great advantages of the machine is its ability to remove weeds right next to the crop plants (Photo 3). Weeds growing right next to the crop plants are the most expensive weeds to remove; this is particularly the case in high density plantings.
The bottom line is that automated weeding has come a long way in just a few short years. The split blade autoweeders greatly improved the capacity to remove a significant number of weeds from production fields. The advent of autoweeders that can precisely apply an herbicide or laser energy to weeds that are right up against crop plants takes autoweeding to a whole new level and opens the possibility for machine weeding to remove sufficient weeds from a field so that little to no follow-up hand weeding is necessary during a crop production cycle. This is truly extraordinary.
- Author: Heidi Aufdermaur
The Master Garden handbook defines a weed as “a plant growing where it is not wanted.” For the home gardener, a plant can become a weed when it interferes with intended use of land and water resources.
I recently purchased “Weeds of California and other Western States” a two-volume resource book. It lists over 1600 pages of plants considered weeds. As I read through this book, I see many plants listed that I would not have considered as weeds, such as the broadleaf forget-me-not. I love the look of this annual. I scattered their seeds several years ago in one area of my yard and this year I found them growing in several other places. This isn't surprising as I've observed their seeds attached to my clothes and garden gloves.
So, is it a weed if this pretty flower shows up somewhere else? According to the California Invasive Plant Council, the answer is “yes,” since this particular plant is also considered invasive. It can escape landscapes and move into natural habitats and pastures. The control of invasive plants in California costs over $82 million dollars per year.
Nostalgic Weeds
One “weed” I enjoy came from my grandmother's garden, it's called the “three-corner leek”. This “weed” looked so pretty in her yard, I brought it home many years ago. Now, I see it made itself comfortable all over the yard. This perennial bulb, with white umbel-like flowers, has “escaped cultivation as a garden ornamental”, according to the “Weeds” book. It has been somewhat easy to control, and I dig out the bulb when it appears. I think of Grandma when I see it, so in the garden, it's staying.
A Weedy Menace
I am slowly winning the fight in two areas where these weeds are located. However, under the birch trees, I have surrendered to taking my garden knife and cutting off the greens just below the surface of the ground. I know it may not be a permanent solution, but it looks good until I need to cut the greens again, in a few weeks. The “Weeds” book says this process eventually “depletes bulb energy reserves.” I have learned not to let this plant set flowers as it also reproduces itself using seeds.
I am determined to win this battle against the weeds with perseverance. Wish me luck!!! I hope to see your comments on how you are doing controlling weeds in your garden.
UC IPM Home and Landscape Pests - Weeds
http://ipm.ucanr.edu/PMG/menu.weeds.html
California Invasive Plant Council
https://www.cal-ipc.org/
Weeds of California and Other Western States, vol. 1&2, UC ANR publication 3488
http://anrcatalog.ucdavis.edu
For more information about Stanislaus Master Gardener's program and upcoming classes, sign up for the Stanislaus Sprout blog at https://ucanr.edu/blogs/StanislausSprout
A Help Desk is also available to help with other gardening questions or concerns: https://ucanr.edu/sites/stancountymg/
Heidi Aufdermaur is a graduate of the 2019 Class of Master Gardeners in Stanislaus County.
Editor's note: Master Gardeners are keeping busy in their own gardens during Napa County's “Shelter in Place” directive. It's spring, it's getting warmer, it's a great time to work in the garden! Here's how Master Gardeners are spending their time:
by Melody Kendall
One of the positive things in my life since the ‘shelter in place' order is my garden. It is my refuge and escape. Who knew that the family that I love more than words can express could drive me so bananas! So, I am out in my garden much of the time just puttering around.
Recently, I have been taking my frustration out on the weeds. February had many warm days and no rain, but the weeds are, of course, flourishing. Doesn't it always feel that way? You can purchase a plant and baby it along knowing full well there are no guarantees it will survive. But a weed will persevere under what seems to be the worst conditions, and despite fervent wishes and efforts aimed at its demise, will look healthier every day.
To discourage those pesky weeds I have two methods I have found to be the most successful. First is decapitation to the ground level using of a stirrup-style hoe. I use it in garden beds and loose mulch and gravel areas. I used to laboriously pull the weeds out and then till the soil, but I have since learned that leaving the roots of the weeds in the soil and using minimal tillage can actually benefit the soil health.
The second method I use on compacted areas like my decomposed granite paths and seating areas is a spray herbicide. This way I don't disturb the compacted surface when I kill the weed. With the recent research into the use of glyphosate and possible unwanted secondary effects of its use, I decided to look for an effective safe alternative for weed control. I found some interesting data on the use of white vinegar that has acetic acid as the active ingredient.
It isn't a ‘magic bullet' but there have been some positive results with the use of white vinegar. The white vinegar in my kitchen is only a 5%-8% concentration and considered safe as a weed killer with a minimum risk factor. Any product with a concentration of acetic acid of 8% or more must be EPA-registered as an ‘active ingredient' as a pesticide product, and I can understand why a higher concentration is dangerous. So, I decided to give the household white vinegar a try. No matter what concentration vinegar you use, it can be harmful to your eyes and skin, so protect yourself by wearing eye goggles and gloves.
I purchased a gallon of white vinegar in the salad dressing aisle at the grocery store. After gloving and goggling up, I filled my pump sprayer with the undiluted 5% vinegar solution and headed out to the garden on a mission. It is very satisfying to spray all the little weed seedlings and to return the next day to brown, desiccated and very unhappy weeds. Sometimes it took more than one application, but responsible use of something better for me and the environment has great satisfaction that helps justify the extra work.
It is important to note that you need to clean all your equipment thoroughly immediately after use. I thought I'd keep a spray bottle full of vinegar ready to spritz random weeds at will - not a good idea. Within a week the spay mechanism was corroded because the acetic acid had eaten through the gaskets. Protect your equipment and always clean it thoroughly after use.
There are multiple ‘wins' to my adventure. I know the weeds will never be entirely eradicated in my yard (there are always weeds seeds waiting for that perfect spot to light), but I now have another method in my arsenal to relieve some stress with an added benefit of feeling good about the methods I have chosen.
Happy weeding.
References:
Northwest Center for Alternatives to Pesticides http://www.pesticide.org/vinegar_herbicides
Soil info: UC Integrated Pest Management http://ccmg.ucanr.edu/files/141617.pdf
UC Davis-Vegetable Research and Information Center https://anrcatalog.ucanr.edu/pdf/7248.pdf
During Napa County's shelter in place directive that protects everyone's health and safety, Napa Master Gardeners are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143. Volunteers will get back to you after they research answers to your questions.
Visit our website: napamg.ucanr.edu to find answers to all of your horticultural questions.
Photo credits: "Summa"- Pixabay free picture