- Author: John Lovett
- Posted by: Gale Perez
Pair of studies offers evidence into "superweed's" defensive tactics, strategy
FAYETTEVILLE, Ark. — A study of the effects of mowing on a common weed has found that what doesn't kill you can make you stronger.
A study published in Nature's Scientific Reports has found that frequent mowing of Solanum elaeagnifolium may help create a “superweed.”
Solanum elaeagnifolium — also known as silverleaf nightshade — can be found from south Texas to South Africa and Greece, infesting fields and soaking up valuable nutrients intended for cash crops. The weed with purple flowers – sometimes white and light purple – has prickly spines and poisonous berries.
Relatives of the plant, including Solanum ptychanthum or black nightshade, and Solanum carolinense, or Carolina horsenettle, also produce toxic berries and are native to Arkansas. It's a family that also includes some friendly crops such as tomatoes, potatoes, peppers and eggplants.
Rupesh Kariyat, an associate professor of entomology and plant pathology with the Arkansas Agricultural Experiment Station, has been studying silverleaf nightshade for more than a decade. Kariyat began the study while at the University of Texas Rio Grande Valley, when he and his graduate student Alejandro Vasquez took on what turned into a five-year, two-part study to observe the effects of frequently mowed silverleaf nightshade. Kariyat joined the experiment station, the research arm of the University of Arkansas System Division of Agriculture, in 2022.
Although studies have often highlighted weed fitness and defense traits resulting from disturbances like mowing, most were limited to foliar, or leaf, defenses, Kariyat said. That changed when Vasquez and fellow master's biology students at the University of Texas Rio Grande Valley monitored fields of mowed, unmowed and frequently mowed silverleaf nightshade in and around Edinburg, Texas.
“Alejandro's question was, ‘how do these flowers differ between mowed and unmowed plants?'” Kariyat said. “‘And does that have consequences for the insects that actually feed on them?'”
Self-defense strategies
Findings in both studies showed that the more silverleaf nightshade was mowed, the more it developed ways to avoid destruction, Kariyat said. The taproot went down further, nearly 5 feet deep, in the first generation of mowed plants. More spikes popped out on the stem as a defense against caterpillars feeding on the flowers. The flowers became more toxic to caterpillars, leading to less pressure from natural predators.
Like time bombs, the plant produced some groups of seeds that germinated faster and others that were delayed. This “staggered” germination was the plant's way to ensure survival over the long haul.
“You are trying to mow these plants so that the plants are getting eliminated,” Kariyat said. “But what you are actually doing here, you are making them much worse, much stronger.”
Tilling areas with silverleaf nightshade also spreads the plant because the rhizomic roots, like many weeds, can propagate asexually over multiple years and growing seasons.
The observations of mowed, unmowed and frequently mowed areas with silverleaf nightshade provide evidence that could prompt further studies by weed scientists on best management practices, Kariyat said.
Since the studies focus solely on silverleaf nightshade, Kariyat said other weeds — even the plant's family relatives — may or may not react the same way to frequent mowing. However, the study does provide more insight into the defensive capabilities of plants pitted against human disturbance.
“This should be something that we consider when we make management plans,” Kariyat said of the plant's defenses. “Management practices need to be better understood using the ecology and biology of the species and the other species which interact with them.”
Kariyat and Vasquez published their results in April with an article titled “Continuous mowing differentially affects floral defenses in the noxious and invasive weed Solanum elaeagnifolium in its native range.” Vasquez, now an entomology and plant pathology Ph.D. student at the University of Arkansas, was the lead author. Co-authors included Kariyat, Alexa Alaniz, and Robert Dearth, founding director of the School of Integrative Biological and Chemical Sciences at the University of Texas Rio Grande Valley.
“As scientists, we want our research to be accessible and applicable to anyone, and mowing is a concept the world at large can understand,” Vasquez said.
The initial study was published in 2021 with an article titled “Local adaptation to continuous mowing makes the noxious weed Solanum elaeagnifolium a superweed candidate by improving fitness and defense traits.” The lead author for that study was Jesus Chavana, with co-authors Sukhman Singh, Bradley Christopherson, Alexis Racelis, Vasquez and Kariyat, all with the University of Texas Rio Grande Valley at the time.
For more on the topic, please check out the Food, Farms & Forests podcast episode “Mow less: Studies Show Less is More When Mowing Noxious Weed.”
John Lovett is the Science Writer with Agricultural Communications Services at the Arkansas Agricultural Experiment Station, University of Arkansas. He can be reached at jlovett@uada.edu or (479) 763-5929.
Original source: EurekAlert! • June 3, 2024
/h3>/h3>
For many of us, gardening involves a constant battle with weeds. Basically, a weed is nothing more than a plant growing where it is not wanted, the classic example being dandelions in the lawn. But as the old saying goes, “One man's trash is another man's treasure,” and there are many “weeds” that are, in fact, completely edible. Good examples are purslane (portulaca oleracea), miner's lettuce (claytonia perfoliate) and, yes, even the unwanted dandelion; many tasty recipes for them can be found in a simple internet search. Looked at another way, a weed may simply be an unloved flower.
According to the Farmer's Almanac, weeds fall into three distinct categories: weeds, noxious weeds, and invasive weeds. A (basic) weed is simply a plant that causes health problems for either humans or animals (as in allergy seasons when certain grasses, seeds, or pollens are released) or causes economic losses or ecological damage, or is simply undesirable where it grows (crabgrass is a classic example). A noxious weed is any plant designated by federal, state, or local government as one which can cause injury to agriculture, wildlife, public health, recreation, or property. Noxious weeds vary from state to state and county to county (field bindweed is noxious in California). An invasive weed is a non-native that competes with natives and may crowd them out and alter ecosystems (English ivy, for example, which has also become invasive in Bidwell Park).
There are precautions to take that will help prevent the spread of unwanted seeds. It is important to make sure gardening tools and pots are cleaned after each use, a step that many people overlook. Immediately clean tools that have been used to remove dead or diseased leaves. If and when purchasing soil and amendments at a garden center, be sure to buy quality materials that are comprised of manure, compost, or “garden” soil that are preferably weed free. Although more expensive, selecting an amendment known to be weed free is worth the investment.
Once your plants are getting established, try to water them by hand or through a drip system. Limiting water applications to areas around your plants' roots will discourage any stray seeds from germinating nearby. Avoid over-fertilizing: over-fertilization encourages more vigorous competition with your plants from any weeds that may be present.
It may take several seasons, but by being diligent weeds can be controlled. It is especially important to remove them before they flower and produce seed. UC weed scientists counsel that “one year's seed results in seven years of weeds.”
It is also helpful to remember that in nature, weeds play an important role. They can resist conditions like drought, acidic soil, lack of humus, and mineral deficiencies. Weeds protect topsoil from eroding away in heavy rains and strong wind. They provide cover and shade for soil microbes and insects. And weeds can reveal important information about the health and pH of our soils -- for example, certain weed species are confined to acidic soils and others to alkaline. The presence of some weeds, like Curly Dock, let you know that soil in the area is frequently wet and saturated. So don't dismiss the weeds in your yard out of hand – they may have something useful to tell you!
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.
- Author: Jeanette Alosi
Puncturevine (Tribulus terrestris) is an attractive green plant with small yellow flowers commonly seen growing prostrate along the side of the road.
Unfortunately, there are is no easy way to control this noxious weed. For most homeowners, the mechanical control methods of hand removal or cutting the plant off at the taproot are most effective. Any seeds left on the ground must be removed by raking or sweeping. Use heavy gloves to protect hands from the spiky seedpods. Of course, as with any weed, it's best to remove it before it flowers and sets seeds. This is especially important for puncturevine, as seeds are viable for years, and can be spread by shoes or the wheels of lawn mowers or carts.
Biological control using several species of weevils have been tried but are not always effective. Chemical control of puncturevine in the home garden is often unnecessary. However, in heavily infested areas, or when hand removal is difficult, herbicide may be an option.
For more information on puncturevine see the IPM Pestnote No. 74128 and the IPM Weed Gallery.
- Author: Guy B. Kyser
Puncturevine (Tribulus terrestris) kept a low profile during the drought years but seems to have exploded following this year's rains. (It is still ‘lying low', so to speak, but there is a lot more of it.)
Also known as goatheads or caltrop, puncturevine is a prostrate annual that produces large, hard, spiked seeds. The seeds disseminate by sticking to animals, tires, and feet, and can easily puncture bike and ATV tires. I tried to do a puncturevine study once but couldn't get the seeds to germinate; my theory now is that the seeds have to be run over by a vehicle before they'll sprout. Conveniently, the plant is commonly found along dirt roads, on roadsides, and on the edges of ag fields.
Puncturevine is native to southern Eurasia and Africa. It is in the plant family Zygophyllaceae, which also includes the creosote bush native to the Mojave Desert.
Extracts from puncturevine seed and other plant parts are available as a dietary supplement, and are reputed to boost virility. I'm guessing this is a holdover from the old medical idea of homology, where the shape of a plant suggested the ailment it was supposed to cure. And the puncturevine seed looks sort of like a goat head, and goats are, you know, lusty. However, WebMD says “Taking tribulus as a supplement for a short time is probably safe, provided that you're healthy and you are not pregnant or breastfeeding.” Hardly a ringing endorsement.
Two species of weevil from puncturevine's native range have been introduced into the U.S. They help keep puncturevine populations in check but they seem to be locked in a boom-and-bust cycle with the plant: when puncturevine populations crash, so do the weevils, and the plant resurges the following year.
More information on this species, including methods for control, are available in a Weed Report at the Weed Research and Information Center and in UC-ANR's Pest Notes.
- Author: Gale Perez
11/9/2016 • Woodland, CA
11/16/2016 • Salinas, CA
11/17/2016 • Fresno, CA
12/13/2016 • Eureka, CA
12/14/2016 • Susanville, CA
The direct annual cost to monitor and control invasive plants in California is $82 million, and the indirect economic impacts are even larger. Join the fight to reduce noxious weeds and get trained at the 2016 Workshop Series!
- Highlights of cost-effective approaches that maximize success
- Showcase of effective strategies to manage invasive species--plants and wildlife
- Featuring reduced-risk practices while promoting biodiversity
- Discussions of economic losses caused by invasive species on rangelands--forage value and livestock toxicity
- Weed identification: Bring a weed or plant sample and have it identified by experts
SPEAKERS:
- Joe DiTomaso, UC Davis Professor and UC Cooperative Extension Non-crop Weed Specialist
- Ken Tate, UC Davis Professor and UC Cooperative Extension Rangeland Watershed Sciences Specialist
- Morgan Doran, UC Cooperative Extension Livestock and Natural Resources Advisor
- Marcia Booth, Senior Analytical Chemist, California Animal Health and Food Safety Laboratory System, UC Davis
- Guy Kyser, UC Davis Weed Science Specialist
- Elise Gornish, UC Cooperative Extension Restoration Ecology Specialist
- and more...
COST: $15 (includes materials, lunch and refreshments)
For additional details and to register visit www.KnockOutWeeds.com.
/span>