- Author: Jeannette Warnert
Weeds present a serious economic problem for farmers, a major headache for vegetable gardeners, and an unattractive appearance in landscapes, but herbicides are not the only solution.
“Studies have shown that more than 70 percent of weeds in lawns and ornamental plantings can be controlled based on good cultural practices,” said Dr. Clebson G. Gonçalves, a horticulture expert and farm advisor with UC Cooperative Extension in Lake and Mendocino counties. He spoke about springtime weed identification and management during a recent urban horticulture webinar offered by the UC Integrated Pest Management Program. “To control weeds, start with good soil; choose suitable plants; and mow, prune, water, and control pests to ensure dense and healthy turf and ornamentals.”
There are several definitions for the term “weeds,” but generally speaking, it can be defined as a plant out of place. Gonçalves used common bermudagrass as an example.
“Bermudagrass is one of the most desirable grass species for golf courses, sports fields, and residential lawns. But out of place, it's extremely difficult to control. It's adaptable to a wide range of environments and can reproduce by rhizome, stolon, and seeds,” he said.
When deciding how to control weeds in lawns and landscapes, Gonçalves suggests gardeners start by identifying the species. The Weed Research and Information Center at the University of California, Davis, offers a free online weed identification tool. Users input characteristics of the weeds – such as weed type (grasslike, broadleaf, woody), where the weed was found, leaf characteristics, stem characteristics, floral characteristics, life cycle, growth habit, etc. – and the tool offers potential species. The UC IPM Program maintains a weed photo gallery of species commonly found in California.
Knowing the species helps determine best practices for control. For example, nutsedge is a grass-like weed that develops nut-like tubers on the roots. The tubers are key to nutsedge survival. Dig deeply into the soil to remove the tubers on mature nutsedge roots. To limit tuber production, remove small nutsedge plants before they have 5 to 6 leaves.
Gonçalves suggests following the principles of integrated pest management to control the weeds by first considering practices that are effective and environmentally sound.
Preventative
- Avoid bringing weeds into your garden and landscape in the first place. Gonçalves suggests using weed-free soil and compost. “It's better to spend a little more money up front when you buy topsoil and compost, than spending even more money later for weed control,” he said.
- Inspect plants at nurseries before bringing them home to see if there are any weeds in or under the pot.
- Clean the mower between lawns. “This is especially important for landscaping companies that work in different locations on the same day. It is important to clean all the equipment before starting in a different location.,” Gonçalves said.
- Never let weeds go to seed. “A lot of species – such as dandelions, bermudagrass, and annual bluegrass – can produce a new seed head very quickly,” Gonçalves said. “If you mow every other week, that's enough time for these weeds to produce new seed heads and disperse seeds. It's better to mow once a week or even more often to prevent the production of seed.”
Cultural
- Soil aeration. “It's very important to alleviate soil compaction in established turf. You will have better water infiltration, greater nutrient availability and more oxygen underground, which promotes plant health and growth above and below the ground,” Gonçalves said.
- Don't leave soil exposed. Limit the area for weeds to grow by utilizing dense plantings. “When you have light and moisture, you have weeds coming up,” he said.
- Mow uniformly at a height of three inches or more. The tall and dense turfgrass canopy will shade the ground and prevent the germination of several weed species.
- Fertilize uniformly.
Mechanical
- Pulling weeds. “Every weed can be controlled by hand. If you have the time to pull by hand, that is recommended. There is some pleasure in pulling weeds. It can be used as therapy,” Gonçalves said.
- Mulches. Wood chips, stone, leaves or compost – especially on top of landscape fabric – can control weeds.
- Flaming. Very effective, primarily in the early stages when weeds are small in stature. But if they are aggressive weeds with strong taproots, such as dandelions and buckhorn plantain, they can grow back very quickly.
Herbicides
- Organic. Always use certified products. “Don't make homemade herbicides. They are still pesticides and can be dangerous,” Gonçalves said. Corn gluten meal is the only organic pre-emergent herbicide. Organic herbicides are available for consumers in different combinations and concentrations. “Vinegar-based herbicides can be very expensive, but other options such as citric acid-based, caprylic acid-based, clove-oil-based, or ammonium nonanoate-based can be more affordable and provide vinegar-like weed control,” Gonçalves said.
- Synthetic. “Many synthetic herbicides also are available for consumers. But the question is: Do you need it? Keep in mind that, all options presented above must be considered first before deciding to use herbicides,” Gonçalves said.
- In both cases, synthetic and organic herbicides are pesticides. Carefully read and follow the label directions.
Learn more:
- Author: Jeannette Warnert
A collection of small raised beds decorated with colorful scarecrows, quaint décor and several rabbit topiaries make up Mr. McGregor's Garden, but this one doesn't have mischievous Peter Rabbit nibbling on the fruit and vegetables. The main problem appears to be snails. Last fall, dozens of garden snails were found feeding on the leaves of napa cabbage, cauliflower, kohlrabi and broccoli plants.
The Master Gardeners have been searching for organic solutions to the problem. Picking them off one by one has been the first line of defense. The Farmers Almanac suggests spreading crushed egg shells to deter snails from garden beds, and we tried it. However, the UC Integrated Pest Management program reports that egg shells are an ineffective deterrent, and we have seen little improvement.
Another solution available to Fresno County gardeners are decollate snails. Decollates are small, thin, tapered and easy to distinguish from the familiar larger, rounded brown garden snails. The decollate is native to North Africa and the Mediterranean region. It was accidentally introduced to Southern California in the 1960s, and has since helped manage snails in gardens and agricultural settings throughout Southern California and parts of the San Joaquin Valley. It is legal to purchase and release decollates only in the California counties of Fresno, Imperial, Kern, Los Angeles, Madera, Orange, Riverside, Santa Barbara, San Bernardino, San Diego, Tulare and Ventura. Because of its potential adverse impact on certain endangered and native mollusks, they should not be used in any other places in the state. Even in counties were decollate snails are permitted, they should not be introduced in or near natural areas because of the potential danger to native snails.
“Literature says it takes four to eight years for decollate snails to control brown snails, but my experience is they'll clean them out in a year,” Woods said.
The decollates are easy to find throughout Woods' front and back yards, under rocks and plants and nestled in plant litter. In February, Woods donated about 30 decollate snails to the Master Gardener's Children's Garden. The decollates were dispersed among strawberry and vegetable plants. While not a scientific trial, our experiment may lead to fewer snail and slug pests and less leaf damage in the coming years.
More information:
Visit the UC Master Gardeners Children's Garden in the Garden of the Sun, 1750 Winery Ave., Fresno. Hours: 9 to 11 a.m. Monday, Wednesday and Friday.
How to manage snails and slugs, UC IPM
UC IPM Natural Enemies Gallery, decollate snails
Identify snail damage, UC IPM (YouTube video)
- Author: Jeannette Warnert
So, it's also a good time to think about ways to prevent the movement of herbicides, pesticides, fertilizers and other contaminants off the property and into waterways, where they can cause environmental harm.
“Pesticides applied to lawns and gardens can be washed into gutters and storm drains. Eventually they will end up in our creeks, rivers or oceans,” said Karey Windbiel-Rojas, associate director for urban and community integrated pest management (IPM) and area IPM advisor for Yolo, Solano and Sacramento counties. “A lot of people think this water goes to a water treatment plant and gets cleaned up, but that's not the case.”
Windbiel-Rojas suggests using IPM practices to deal with crabgrass and other unwanted pests around the home and landscape.
IPM involves monitoring the lawn, landscape plants and gardens and carefully identifying what is causing problems. Decide whether you can tolerate a small amount of weeds. Determine whether the issue can be prevented with cultural or mechanical solutions, such as adjusting irrigation and hoeing for weeds. If this doesn't solve the matter, select chemical materials that are the least-toxic option available.
Controlling crabgrass with IPM
Crabgrass was introduced from Eurasia and is now widespread in the United States. Its thick leaves and clumping habit look unattractive in a uniform lawn. To prevent crabgrass, keep turf heathy and dense to out-compete weeds by selecting a turf species that is suited to the climate; mowing the lawn at the proper height; and overseeding, fertilizing and irrigating properly. A few clumps of crabgrass can be weeded out with a trowel or other tool.
“If you tried all the non-chemical tools, and you're not getting the level of control you are looking for, considering a pesticide may be warranted,” Windbiel-Rojas said.
Preventing environmental contamination
- Prevent water runoff. Take note of the soil slope, texture, saturation and amount of vegetation. Use these factors to decide where to treat weeds and other pests with chemicals. Irrigation overspray is a common cause of runoff that washes materials off paved surfaces. In dry climates, summer runoff is primarily from overirrigation or overspray.
- Don't over water. Rain and excessive irrigation can cause a pesticide to leach into the ground, eventually contaminating the water table.
- Be aware of pesticide characteristics. Some pesticides are more water soluble; others attach or absorb to soil particles that can move off site.
- Keep applications on target. Pesticides accidentally sprayed onto paved surfaces, cracks, crevices, sidewalks, parking areas and hard-packed dirt will quickly run off. Use hardscapes that limit runoff, such as decomposed granite or flagstones between vegetated areas. Create a buffer zone around the edges of the treatment area and around yard drains where you avoid pesticide application to prevent the chemical's movement off site.
- Watch the weather. Rain can carry pesticides away from the application site. Don't apply pesticides if there is any rain forecast. Wind can blow pesticide droplets, dust and grains away from the intended pesticide target. Pesticide application should be done when there is very little or no wind. High temperature and low humidity increase pesticide volatility. A lot of labels will say not to use the product above a certain temperature.
“Many pesticides are available for residential use,” Windbiel-Rojas said. “When buying them, be sure to read the entire label. Do a little research on the active ingredient in the pesticide to learn whether it effectively treats the pest you are targeting, and has the lowest environmental impact.”
Learn more:
Pests in Gardens and Landscapes: Crabgrass, UC IPM
Pesticides and Water Quality (August 18, 2022)
Presenter: Karey Windbiel-Rojas, Associate Director for Urban & Community IPM/Area Urban IPM Advisor
Watch the recording on YouTube
- Author: Jeannette Warnert
Early morning birdsong, hummers darting around flowers and tiny doves in patio nests are enchanting. Without the farmers' concern about profit, gardeners can more readily forgive the occasional pecked fruit, stolen nuts and avian grazing on freshly planted vegetable seeds.
UC Cooperative Extension human-wildlife interaction advisor Breanna Martinico said during a webinar presentation that integrated pest management techniques can be used to maximize bird benefits while minimizing the damage they can cause.
She suggests starting with identification.
“Bird ID is fun,” she said. “Sit in the backyard with a cup of coffee, binoculars and a bird ID guide and get to know what birds are using your backyard. It's a great way to relax and connect with nature. You might be surprised what you find that you weren't noticing before.”
If birds are causing a problem, cultural practices – such as exclusion with netting or frightening with bird distress calls or fake predators – are more effective than control. “Be sure to include a cost-benefit analysis when deciding on bird deterrents or exclusion,” she said. “It may be best to tolerate damage if it is minimal.”
Lethal control is strictly regulated and rarely the best choice. Many birds in the U.S. are protected under the Federal Migratory Bird Treaty Act. It is illegal to kill or capture migratory birds or destroy their eggs or nests. Game bird hunting is regulated by the California Department of Fish and Wildlife and limited by location and hunting seasons.
Martinico's talk was more focused on supporting bird populations by making gardens welcoming to birds, and gaining an appreciation for the beneficial role bird species play in California.
She shared the results of recent research on Western bluebirds and songbirds that used forensic DNA analysis of droppings to determine exactly what birds are eating.
“They eat incredible amounts of insects,” Martinico said. “If a particular insect is abundant and becoming a pest, they are effective at reducing pest numbers.”
Sometimes birds that have a reputation for eating desired crops only do this during certain seasons, while at other times they are gardeners' friends. Blackbirds, for example, eat insects in the spring when they need a protein-rich diet to feed their young. They only need to be scared away in late summer, when their flocking behavior becomes more prevalent, and they switch to grains and seeds.
Welcome birds to the garden
Invite birds to your garden by growing diverse, complex landscapes with food and water sources. Large monocultures, like lawns, can have ample resources for pests, but not enough to support other species that might reduce pests, Martinico said. Grow native plants and large trees, and place nest boxes for pest-eating birds like barn owls, ash-throated flycatchers, Western bluebirds, tree swallows and house wrens. Raptor perches will give birds of prey a place to hunt for gophers and other rodents.
When there is bird activity in the backyard, particularly nests with eggs or chicks, minimize the presence of people, cats, dogs, noise and bright lights at night, Martinico said.
Resources:
Birds on home and landscape tree fruit and vines, UC Integrated Pest Management Program
Songbird nest box plans, North Carolina State Extension
Barn owl nest box plans, Wild Farm Alliance
Information about local bird populations, Nestwatch, Cornell Lab of Ornithology
Birds: Friends or Foes? webinar on YouTube
Breanna Martinico, Human-Wildlife Interactions Advisor, Napa, Lake, and Solano counties
- Author: Richard Hardwick
- Author: Laura Berger
Introduction
The tobacco budworm will bore into the flower buds. Look for the caterpillar or its frass inside the buds. The caterpillar is under one-inch long, green, yellow or brown with white or black markings. The adult moth has a wing span of about 1½ inches and is brown/green in color.
According to the University of California, budworms feed on geraniums, petunias, snapdragons and roses as well as a lot of agricultural crops, fruits and vegetables, and many horticultural plants. Evidence of their arrival are tiny round or oblong 1/16-inch holes in flower buds, 1/8-inch holes in leaves and blooms, and black seed-like droppings. Flowers that open after budworm infestation have damaged petals and a budworm can destroy several flowers per day. The plant may cease flower production completely if severely infested. The budworm may move on to consume leaves and foliage also. The budworms peak in late summer. When mature, the larva drops to the ground and pupates in the soil. They can have 2 to 4 generations in a season, overwinter in the soil, and emerge as a moth again during the next growing season.
Management
Use Integrated Pest Management (IPM) for successful plant problem management.
Non-chemical management
Manage weeds in and around gardens to remove the habitat and alternate food sources for the tobacco budworm.
Monitor plants closely for damage. Handpick and destroy larvae and infested buds on roses. Hand pick caterpillars or prune out and promptly dispose of infested buds or rolled leaves (often hiding caterpillars within).
Scout for larvae at dusk, when they are most active. Check for actively feeding larvae, small holes in buds and flowers, and caterpillar droppings (frass or feces) associated with damaged buds.
Chemical management
Bacillus thuringiensis (Bt) is somewhat effective if applied when eggs or damage are first noticed. However, Bt must be consumed by young, actively feeding larvae and only works where the young larvae are feeding on the SURFACE of the plant. Bt is NOT effective against larvae feeding within buds and will not provide reliable control of mature larvae.
Damage is usually not severe and treatment with pesticides not generally necessary. Leaf-feeding caterpillars can be reduced with the microbial insecticide Bacillus thuringiensis or the insecticide Spinosad. These materials will be most effective when caterpillars are small, however caterpillars within buds are unlikely to be killed. Damage may not be noticed until after caterpillars are full grown and no longer vulnerable to insecticide applications.
References
https://ipm.ucanr.edu/PMG/PESTNOTES/pn7466.html
https://entnemdept.ufl.edu/creatures/field/tobacco_budworm.htm
https://www.gardeningknowhow.com/ornamental/flowers/roses/budworms-roses.htm
https://ucanr.edu/datastoreFiles/268-758.pdf
https://hortsense.cahnrs.wsu.edu/fact-sheet/rose-tobacco-budworm/
