- Author: Thomas Getts
A few months ago Rob Wilson wrote an excellent blog highlighting perennial pepperweed patches he was seeing in the Klamath Basin. It is a terrible noxious weed, which is found throughout much of the state, from sea level up to 8,000 ft. in the Sierras.
Where I live in the Honey Lake Valley, perennial pepperweed is widespread and has completely overtaken vast acreages of unmanaged pastures and riparian areas. At one point, it was estimated around 64,000 acres of land were infested throughout Lassen county. Generally, the Honey Lake Valley and Long Valley are hotspots that contain the majority of the acreage. While I live in the Honey Lake Valley, I also travel and work in many other valleys throughout northeastern California. I have found the perennial pepperweed population where I live is infamous. Ranchers and land managers see what a problem pepperweed has become in the Honey Lake Valley and want to keep it out of the numerous other valleys where it is not established.
Pepperweed in the Honey Lake Valley
One of these areas is Sierra Valley south on highway 395 and east on highway 70 over Beckwourth Pass. While there are isolated pockets of pepperweed which exist in Sierra Valley, ranchers and land managers have been vigilant to control it as the last thing they want is for their mountain valley to be overtaken like the Honey Lake Valley.
While perennial pepperweed can be a very difficult species to control, there has been a tremendous amount of research investigating the best ways to manage it on the landscape (James Young and Mark Renz and Rob Wilson to name a few). Often a combination of herbicides and physical techniques are utilized to target the deep, extensive, tuberous root system. Generally, herbicides such as glyphosate, 2,4-D and chlorsulfuron (Telar) have been shown to be effective. Both 2,4-D and Telar are generally selective, and can be applied relatively safely to perennial grasses in established pasture. Telar has soil residual activity, and in research done years ago by Wilson and Renz has shown it to offer better multiyear suppression compared to 2,4-D. Some of my more recent trials in the Honey Lake Valley have replicated what the previous research has shown (Figure one).
Figure One: Pepperweed control from a trial in the Honey Lake Valley
A couple of years ago, I was approached by a land manager in Sierra Valley who had been applying Telar to his pepperweed population with limited success. Initially, I assumed that something probably wasn't being done quite right. Maybe the application timing was off? or maybe they were not properly calibrating their sprayers? I met with the land manager and we walked though his calibration methods, and I double checked his math. Everything seemed to be in order. We even tested the well water, and it also appeared to be fine quality.
As I couldn't find anything on the surface, I figured it would be worth putting out a small replicated field trial to investigate his lack of control. The pepperweed patches on site were small, and one of the largest ones only had room for 5 treatments replicated 3 times. We tried two rates of Telar, MSO and NIS at the high rate, and 2,4-D as standard. Pompously, I expected that my applications of Telar would work, but I couldn't have been more wrong!
Looking at the treatments one year after application, I was only getting suppression, not control with any of the Telar applications (20-40%). The plants were stunted, but not controlled (Figure two). Where 2,4-D looked as expected one year after application with about 80% control. Typically 2,4-D gives a good burn down of pepperweed, but the plants start to come back after 1 year, where multiple years of 2,4-D have been shown to be quite effective.
Photo one: Untreated check 12.5 months after treatment at property in Sierra Valley. Plants are alive and well in full bud/bloom stage.
Photo two: Telar 2.6 oz. MSO 12.5 months after treatment in Sierra Valley. Plants are stunted but very much alive and actively growing (35% control).
Photo three: 2,4-D 2 qt. MSO 12.5 months after treatment in Sierra Valley. Plants are stunted and chlorotic, stand is greatly reduced (80% control).
This was confusing to me, and not what I expected: Telar was not effective in my Sierra Valley plots. The land manager was really quite happy with the results of the small plots, as he had been second-guessing himself as to why his applications did not work. The lack of success I saw confirmed what he had been seeing over the past decade with limited effectiveness of Telar for his perennial pepperweed. These results did not reflect results I had seen over on the other side of the hill in the Honey Lake Valley, nor did the results reflect what other research had shown throughout other portions of the west.
Figure two: Pepperweed control from the Sierra Valley Site
But, what was happening? Why wasn't the Telar working?
Generally, the USGS soil survey classified the location as a Remelli clay. It is an area that is not well drained and often sees flooding in the winter. There were Juncus species, perennial grasses, and silver sage also present on the site. I pulled some soil samples on the site to see if there might be some explanation. When the soil samples came back from the lab, they indicated the site had 11% OM and a pH of 6.8. This was nearly double the OM of the research site from in the Honey Lake Valley in 2017, which had a much lower OM and higher pH (6.2% OM and pH 8.6).
Could the unique soil be to blame for the lack of effectiveness of the Telar? Looking at the chemical properties of Telar, I think the soil characteristics could be a contributing factor.
Telar has a moderate affinity for OM, and is considered to absorb to the soil more at a lower pH. Additionally, Telar is broken down by microbial activity in soils with lower pH and adequate soil moisture, both of which were present on site. Conversely in soils with high pH (like the Honey lake site), Telar is not readily broken down by microbes and is considered more mobile in the soil binding less to OM and soil particles. My current theory is that the lack of Telar's effectiveness in Sierra Valley could be tied to the very high OM content of the soil, and lower pH affecting microbial breakdown of the herbicide.
Regardless of exactly what is limiting the effectiveness of Telar, it hasn't been working for the land manager, and didn't work in my field plots! For him, there may be a need to shift control tactics to 2,4-D or to a nonselective product like glyphosate or imazapyr to keep the pepperweed from spreading in Sierra Valley. Unfortunately, what has been effective in one place and time, is not always effective in another place and time. And the explanation to why is often not simple!
- Author: Ben Faber
- Re-posted by: Gale Perez
From the Topics in the Subtropics blog :: March 4, 2020
* * * * * *
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
- Author: Ben Faber
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 & slightly spongy. Sap is milky white, moderately poisonous & 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.
The plump pods produce copious seeds when ripe. The fruit splits down one side and turns itself inside out. The numerous, loosely attached seeds parachute away on silky hairs, dispersed by the wind – on to the next tree or fence.
So the vine is entrained in the tree canopy so you cant 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
- Author: Thomas Getts
Back in 2017, I wrote a brief blog about myrtle spurge being present in Lassen County. Myrtle spurge was evaluated by CDFA and determined to warrant being placed on the A list of noxious weeds here in California. Recently, a local landowner asked me where he could find a list of noxious weeds within the state. This landowner was specifically interested in myrtle spurge, but wanted to know what other species he should be on the lookout for.
Since moving to California, when folks have asked me about noxious weeds I have sent them straight to the source. The CDFA encycloweedia page which lists all of the noxious weed species in the state. When you click on each species, it will bring you to a detailed description of that species, biology, history, pest rating and even various control methods. It is a one stop shop for noxious weed information!
However, when I looked for myrtle spurge on the web page, I couldn't find it…. I thought there had to be a mistake! Upon further investigation by scrolling down to the bottom of the page, I realized that the webpage hadn't been updated since July 15, 2016, well before myrtle spurge was officially listed as a rated pest. It brought me back to school, where teachers always hounded us to pay attention to website dates!
Picture one: Myrtle spurge growing among rocks
But, if all of the updated noxious weeds were not listed on encycloweedia, where were they listed?
With a little bit of digging, I was able to find a webpage with pest rating proposals and final ratings specific to weeds in California. On this page, there were an additional 67 weed species with pest ratings listed. Comparing the original list and this new list, there was an overlap of 25 species which had their rankings re-evaluated and occurred on both lists. Forty two species were only listed on the pest rating proposals and final ratings web page, but not the encycloweedia webpage. This included A ranked species, like myrtle spurge and prickly acacia, as well as C ranked species, like cheatgrass and Sahara mustard. Seven of the 42 species were listed on the D list, which indicates there is no mandated state action needed. Another place I often check for noxious weed ratings is the federal USDA plants database. They have a webpage for each state, listing the noxious weeds species. Out of curiosity, I gave it a gander and only found two of the 35 newly listed species represented on the federal webpage (false pickerel weed and jeweled distaff thistle).
I was confused. Were species listed on the pest rating proposal web page actually noxious weeds, or just proposed noxious weeds? So, I called the CDFA to figure it out! What I found out is that these species have not officially been added to the 4500 noxious weed list, but they are going to be added in the near future. I also found out that even though they are not on the 4500 list, they are still considered rated pests by the state, and should be treated as such!
Noxious weeds are legally required to be controlled/managed under state law, and there are two places to look for species that you need to watch out for. There are 198 noxious weeds listed on encycloweedia, and an additional 35 species listed on the pest rating proposals and final ratings web page. When looking for noxious weeds to manage in California, make sure to check both web pages, not just one. Knowing what weeds are listed is the first step to identifying them in the field and preventing their spread!
The table below lists species named on the newer pest rating proposals webpage but not encycloweedia.
Common name |
Scientific name |
Pest rating |
American eelgrass |
Vallisneria americana Michx. |
Pest Rating: D |
Balloon Plant |
Asclepias physocarpa |
Pest Rating: C |
Barbwire Russian Thistle |
Salsola gobicola |
Pest Rating: B |
Bermuda grass |
Cynodon dactylon |
Pest Rating: D |
Bitou bush |
Chrysanthemoides monilifera |
Pest Rating: A |
Buffel grass |
Pennisetum ciliare |
Pest Rating: D |
Cheatgrass |
Bromus tectorum |
Pest Rating: C |
Coco-Yam, Elephant Ear or Taro |
Colocasia esculenta |
Pest Rating: D |
Dagger-flower |
Mantisalca salmantica (L.) Briq. & Cavill. |
Pest Rating: A |
Egyptian broomrape |
Orobanche aegyptiaca Pers. |
Pest Rating: A |
False Pickerel Weed |
Monochoria vaginalis (Burm. f.) C. Presl ex Kunth |
Pest Rating: A |
False Yellowhead |
Dittrichia viscosa (L.) Greuter |
Pest Rating: A |
Flowering-rush |
Butomus umbellatus |
Pest Rating: B |
Giant Hogweed |
Heracleum mantegazzianum |
Pest Rating: A |
Graceful Spurge |
Euphorbia hypericifolia L. |
Pest Rating: A |
Jeweled distaff thistle |
Carthamus oxyacantha |
Pest Rating: B |
Jewels of Opar/Fameflower |
Talinum paniculatum |
Pest Rating: C |
Jointed bulrush |
Schoenoplectus articulatus (L.) Palla |
Pest Rating: D |
Kidneyleaf Mud Plantain |
Heteranthera reniformis |
Pest Rating: A |
Lily of the Valley Vine |
Salpichroa origanifolia |
Pest Rating: C |
Manchurian Wild Rice |
Zizania latifolia |
Current Pest Rating: A |
Mexican pokeweed |
Phytolacca heterotepala H. Walter |
Pest Rating: A |
Myrtle Spurge |
Euphorbia Myrsinites |
Pest Rating: A |
Old man's beard |
Clematis vitalba |
Pest Rating: A |
Orange Hawkweed |
Hieracium aurantiacum |
Pest Rating: B |
Paterson's curse |
Echium plantagineum L. |
Pest Rating: A |
Pickerelweed |
Pontederia cordata L |
Pest Rating: D |
Portuguese Broom |
Cytisus striatus |
Pest Rating: B |
Prickly Acacia |
Vachellia nilotica |
Pest Rating: A |
Ruby saltbush |
Enchylaena tomentosa R. Br. |
Pest Rating: A |
Sahara Mustard |
Brassica tournefortii |
Pest Rating: C |
Senegal tea plant |
Gymnocoronis spilanthoides |
Pest Rating: A |
Shining cranesbill |
Geranium lucidum L |
Pest Rating: A |
Slender snakecotton |
Froelichia gracilis (Hook.) Moq. |
Pest Rating: D |
Smallflower Hawksbeard |
Crepis pulchra |
Pest Rating: C |
Snail Medic |
Medicago scutellata (L.) Wilson |
Pest Rating: D |
Spanish Heath |
Erica lusitanica |
Pest Rating: B |
Tropical Whiteweed |
Ageratum conyzoides L. |
Pest Rating: C |
Ward's weed |
Carrichtera annua |
Pest Rating: A |
Water hyacinth |
Eichhornia crassipes |
Pest Rating: None |
West Indian Woodnettle |
Laportea aestuans |
Pest Rating: C |
Yellow-Flag Iris |
Iris pseudacorus L. |
Pest Rating: B |
Table One
- Author: Cheryl A. Wilen
I recently attended a Santa Ana River Orange County Weed Management Area (SAROCWMA) meeting and there was an opportunity for participants to update the group about new invasive plants as well as give an update on management of these and others. During the discussion, Ron Vanderhoff from the Orange County Native Plant Society (OC-CNPS), reported new findings of a plant I'd never heard of. In fact, when the group was talking about it, I wasn't sure if I heard the name right.
The plant is called stinknet (Oncosiphon piluliferum), which to me sounds like a game played by 10 year olds. However, the California Invasive Plant Council considers it an emerging invasive weed (http://www.occnps.org/PDF/HYS-Oncosiphon-piluliferum.pdf). On the OC-CNPS weedmapper, it was first reported in Orange County in 2003, but was in San Diego County as early as 1998 and Riverside County in 1981.
According to the USDA-NRCS plants database, stinknet has a limited distribution in the U.S., being found only in Orange, Riverside, and San Diego Counties in California and Maricopa, Pinal, and Yavapai Counties in Arizona. However, Cal-Flora has unconfirmed sightings of it in San Bernardino, Imperial, and Kern Counties.
Stinknet or globe chamomile is a relatively small annual plant that could easily be confused with the turf and landscape weed pineappleweed until you smell it. Pineappleweed flowers have a pleasant sweet smell while, as you may guess from the name, stinknet has the opposite odor. It is most noticeable when flowering (March to July in Southern California) so now is a good time to spot it.
Although it is not listed as a noxious weed, land managers should still be on the lookout for it especially along the coast and inland. It can be particularly damaging in coastal sage scrub because of its tendency to fill in open spaces, and it can reduce growth of other native annuals and impact animals that depend on the openings in these areas.