- Author: Emily Dooley
- Posted by: Gale Perez
AI enables low-cost tracking of invasive johnsongrass
To manage johnsongrass, a noxious weed that crowds out cotton and sickens horses, farmers have tried herbicides, burning and hand-pulling. Now, researchers in the UC Davis Department of Plant Sciences have developed a more high-tech weapon against the invasive weed: artificial intelligence and machine learning.
Using photos from Google's Street View database, the researchers have tracked down more than 2,000 cases of johnsongrass in the Western United States for a fraction of the cost and time that it would take for drive-by or other in-person surveys. They call their tool Google Weed View.
The advancement could help land managers easily and quickly survey for other problem plants.
“Once the model is trained, you can just go and run it on millions of images from Google Street View,” said Mohsen Mesgaran, an assistant professor in the department. “We have huge flexibility, and its capability can be scaled up very quickly.”
The technique can easily be extended to other plant species. All that is needed is to label the new item in Street View photos and train the algorithm to identify that object in the images.
By providing location information, Google Weed View also offers an opportunity to examine how climate affects the growth and spread of weeds and invasive plants at very large scales.
“I think it can be both useful for management and for people with interests in more basic questions in ecology,” Mesgaran said.
A colleague's query
Mesgaran began looking at Google's photo database of roadways, streets and highways after Kassim Al-Khatib, a professor of Cooperative Extension in the same department, asked if he could survey Western states for johnsongrass.
Al-Khatib studies where johnsongrass grows, ways to manage it and how this perennial has evolved to be so prevalent and resilient. He's also working with scientists at the University of Georgia to decode the genome of johnsongrass, which is one of the top 10 most invasive weeds worldwide.
Johnsongrass can crowd out native plants, harbor pathogens and affect agriculture. It grows up to 7 feet tall with flowers that are green, violet, dark red or purplish brown depending on maturity, according to a UC Statewide Integrated Pest Management Program briefing page.
“Johnsongrass is a major weed not just in California but worldwide,” Al-Khatib said. “It's very difficult to control. It's a problem on vineyards. It's a problem for cultivated crops. It's a problem on orchards.”
Google Weed View allows for rapid, convenient scanning. It is continuously updated via everyday users with compatible cameras and images collected by Google. “Instead of a day of in-person driving, we can use AI to determine if johnsongrass is in a county or not,” Al-Khatib said.
Setting the parameters
To find the weeds, Mesgaran went to Google Street View, which hosts billions of panoramic photos. It didn't take long to find johnsongrass.
“The pictures are really good quality,” he said. “You can see plants and flowers.”
Street View's photos offer a 360-degree view, so in his request, Mesgaran set parameters, based on street direction (bearing), to only see the side view. He also specified latitude, longitude and other factors. To train the deep, or machine learning, model, he chose Texas, where johnsongrass is prevalent.
A student sorted through more than 20,000 images from that request to find pictures with johnsongrass, then drew rectangular shapes around the weeds. They located 1,000 images.
The labeled photos were fed into a computer to train a deep learning algorithm capable of identifying johnsongrass in Google's images. The model was run again to capture potentially more images containing johnsongrass. These additional images were then labeled and used to further refine the model. With each iteration, the algorithm learned and became more accurate.
“This deep learning model was trained by these images,” Mesgaran said. “Once we had a semi-working model, we ran it against about 300,000 images.”
For Al-Khatib's request, researchers focused on 84,000 miles of main roads in California, Nevada, Oregon and Washington states. The team discovered 2,000 locations with johnsongrass.
Google Weed View cost less than $2,000 to purchase the images and teach the model. A traditional car survey to cover the same area would cost an estimated $40,000 in gas, hotel, food and other costs.
“In a matter of months, we came up with 2,000 records, and I can do it for the whole U.S.,” Mesgaran said.
Next up? The whole United States.
Media contacts:
- Mohsen Mesgaran, Department of Plant Sciences, (530) 752-0852, mbmesgaran@ucdavis.edu
- Emily C. Dooley, College of Agricultural and Environmental Sciences, (530) 650-6807, ecdooley@ucdavis.edu
- Amy Quinton, UC Davis News and Media Relations, (530) 601-8077, amquinton@ucdavis.edu
Emily Dooley is a Communications Specialist with the College of Agricultural & Environmental Sciences at UC Davis.
Puncturevine (Tribulus terrestris) is an attractive green plant with small yellow flowers commonly seen growing prostrate along the side of the road. A native to Southern Europe, it's also referred to as “goathead.” However, underneath its foliage lies danger: spiky seedpods with needle-point spikes. If puncturevine is stepped on, it is painful to bare feet and dogs' paws; it will pierce and flatten bicycle tires. Because of its spiky seedpods puncturevine is also referred to as “caltrop,” after the spiked metal devices thrown on the roadway to stop vehicles. Caltrops have four projecting spikes with one spike always pointed up; just in the right position to puncture a tire or flip-flop, hence the similarity to puncturevine seedpods.
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 on Puncturevine.
- Author: Kathy Keatley Garvey
Honey bees and native bees love capeweed, Arctotheca calendula, also called South African capeweed, cape dandelion and cape marigold or cape gold.
It's an invasive plant originating from the Cape Province in South Africa (Here's what the California Invasive Council says about it:
"Capeweed (Arctotheca calendula) is an annual or perennial evergreen herb that, when young, forms a low-growing rosette of heavily pinnately lobed leaves, with undersides covered by woolly down. With age, it forms an extensive, dense, mat-like groundcover by proliferation of rooting stems (stolons) from rosettes. Leaves are pinnately lobed; fine, dense hairs cause stems and leaves to appear silvery. Flowers are approximately two inches in diameter, lemon yellow, and daisy-like with yellow centers. The plant is conspicuous in late spring and early summer due to its increase in size and the profusion of large yellow daisies. Plants are seldom solitary, and they spread vigorously by creeping stems (Lasca Leaves 1968)."
Capeweed may have arrived in California in a shipment of grass seed from Australia, where it is a common weed, according to the California Department of Food and Agriculture. The invasive species compendium (CABI) listed it as a noxious weed in 2010 in California.
However, it's cultivated as an ornamental ground cover and has both "fertile" and "sterile" forms.
We've seen lawnmowers run over the the weed in City of Benicia parks (yes, it grows back), we've seen it thriving in a gold carpet along coastal California, and we've seen bees foraging on it.
It's a pollinator paradise, of sorts, but it's also invasive.
- Author: Thomas Getts
- Posted by: Gale Perez
From the Lassen county Farm Advisor's Update newsletter (Aug. 2020)
Highlighting Two Uncommon Noxious Weeds
Let's keep them uncommon!
I'll start with rush skeleton weed. It is relatively difficult to identify when it is young. The leaves and rosettes look fairly similar to a dandelions. As the growing season progresses, it sends up long spindly shoots as it bolts in early summer. After it bolts it looks quite a bit like chicory, but it is much more invasive. (Chicory has larger blue or white flowers.) Eventually it develops a yellow flower and seeds like a dandelion that can blow in the wind.
This plant is not widespread in California and is considered an A-list noxious weed on the old noxious weed list. The map from Cal Flora shows where is has been officially documented within the state. There have been sightings in Plumas county, a couple in Shasta, and there is an established population on the west shore of Honey Lake. I wouldn't be surprised if there are other populations around our region which do not show up on the map!
Skeleton weed has the potential to expand in the Intermountain region, overtaking rangeland and dryland pastures. In conversations I have had with weed scientist Tim Prather, skeleton weed has completely escaped control in his state of Idaho. It has established on over 3 million acres in the mountains of Idaho, and in many parts of eastern Washington. Skeleton weed is not just problematic here in the western US, but is also a problematic plant in dryland wheat production in Western Australia and parts of Argentina. Keep your eye out for it, so we can prevent it from overtaking our landscapes!
Skeleton weed is not desirable forage for livestock or wildlife, and grazing tends to promote skeleton weed over other species that are more desirable. Generally, mechanical control is not effective for established plants because of the deep root system. However, there are multiple biocontrol agents established in the state. A rust, a gall forming midge, and a gall forming mite can all help reduce spread, but not eliminate populations.
Like many deep-rooted perennial weeds, herbicides are often relied upon to control established skeleton weed patches. The best time to make applications is in the rosette stage. If you do find a population on your property, mark the area out now while you can find the plants and see the flowers. The next year, finding the rosette will be easier. Feel free to give me a call to discuss what control options might be best utilized for your situation.
Previously, sulfur cinquefoil was considered an A-list noxious weed, but its status is under evaluation, as many noxious designations are. Regardless of the category it is listed under, it is still a noxious weed, and not one we want to let take over our landscapes. It has the ability to spread by seed, as well as by root, and established plants can live up to 20 years forming a woody crown.
One key characteristic of sulfur cinquefoil compared to other cinquefoils is the stiff hairs that stick straight out from the stem. Many other native cinquefoils have hairs that lay flat on the stem. This can be key to help identify the noxious weed before it goes to flower.
Controlling weeds while patches are small can pay large dividends on efforts needed in the future. If you suspect you may have either of these species, let's eliminate them before their populations really get started in our region.
Original source: Lassen county Farm Advisor's Update newsletter (Aug. 2020)
- Author: Ben Faber
- Re-posted by: Gale Perez
From the Topics in the Subtropics blog :: March 4, 2020
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So I've gotten a few calls lately about this vine with a big green pod that is growing in lemon trees. What is done with it and how do you get rid of it?
Araujia sericifera, cruel vine, moth plant, bladderflower is an escaped ornamental that has become an invasive weed in California. Yes, a pretty vine brought into the garden – “poor man's stephanotis” - and it's gotten out of the garden into southern California. It's in the hills, in abandoned orchards, on backyard fences and when it gets into a lemon tree, it takes some effort to remove it before the seeds spread to other trees and beyond.
Bladderflower is a perennial vine that is very vigorous where it gets summer water. It is a common weed in citrus groves, where it would enshroud & smother entire trees if not controlled. Stems are tough and ropy, leaves thick and slightly spongy. Sap is milky white, moderately poisonous and causes skin irritation. It flowers Aug-Oct and the seed pods are obvious later in the fall. The flowers have a pleasant fragrance like jasmine. The reason for gardeners planting it. Plus it grows fast in our environment.
So the vine is entrained in the tree canopy so you can't spray an herbicide. To get rid of it, it's important to get down to the base of the tree and cut it out at ground level, removing as much of the root as possible. It still can regenerate, so it will be necessary to monitor the site, removing new growth as it might happen. Be sure to use hand protection because many people are allergic to the sap. Just cutting the vine at its base is sufficient to kill it. Removing the rest of the vine is necessary if there are pods, in order to prevent them going to seed.
The upside of the plant aside from the fragrant flowers is that it is an alternative food source for monarch butterfly caterpillars.
Calfflora shows cruel vine spread mostly along the coast south of San Luis Obispo, but it has the potential to spread thoguhout much of California. Currently, in the US, it is only found in California and Georgia. It is in New Zealand and Australia.
Calflora Description and Distribution of Bladderflower
USDA Description of Plant as attachment below:
Araujia sericifera WRA