Convolvulus can be an ornamental plant. There is a reason it is called MORNING Glory. It's why people plant it. It's commonly sold in nurseries. There's a large purple flowered variety that is growing throughout my Ventura city neighborhood. It's quite charming highlighting the orange fruit high in the canopies of citrus and along backyard fences. There are also pink stripped varieties. They also seem to grow well, and when you decide it's time that they had taken over too much of the garden, it's really hard to get rid of them The seeds are everywhere and they lie dormant, ready to emerge to recolonize that orange tree you had just cleaned out.
Listen to Weedologist Lynn Sosnoskie's advise on how to deal with this beautiful menace in the orchards. This podcast is prepared by Phoebe Gordon of UC's "Growing the Valley".
- Author: Rebecca Ozeran
A few months ago, I was asked about the toxicity of various plants in a horse pasture after the death of a miniature horse using that pasture. While many of the identified plants were chemically harmless (such as filaree [Erodium spp] and some native clovers), the pasture did have fiddleneck (Amsinckia spp) and popcorn flower (Plagiobothrys spp), two native forbs with potentially toxic chemistry.
Popcorn flower (above) has small white flowers. Fiddleneck (below) has slightly larger yellow flowers. Both plants have similar overall shapes: slender flowering stems, relatively small leaves, and hairs on all parts except the flowers themselves.
Fiddleneck is a known alkaloid accumulator and popcorn flower is similarly suspected to accumulate alkaloids. There are no cases that I have found where popcorn flower was identified as a cause of toxicity, however. Most research on popcorn flower chemistry focuses on insect herbivores which like to eat plants with alkaloids, to protect themselves against predation (e.g. Hartmann et al. 2004) – but that's a topic for another blog!
Alkaloids are secondary organic compounds produced by many plants. Different types of alkaloids have different interactions with animal biology, some of which are benign or beneficial, and others which are harmful. Some alkaloids you may have heard of include morphine, nicotine, and quinine. Pyrrolidizine alkaloids, the type found in fiddleneck and popcorn flower, have harmful effects. Toxicity often occurs when animals eat feed or hay contaminated with fiddleneck seeds, and some cases have been documented from animals grazing the plant in a pasture. Fiddleneck alkaloids can cause liver disease and death of horses, cattle, and pigs, but sheep seem to be less vulnerable (Craig et al. 1985).
Both fiddleneck and popcorn flower may also accumulate nitrates. Nitrates convert into nitrites once the animal eats the plant. Nitrites then react with hemoglobin in the blood and make it unable to carry oxygen. This oxygen deficiency can cause death in a matter of hours depending on the concentration of nitrates in the animal's diet. Sheep, pigs, and horses seem more resistant to nitrate poisoning while cattle are most vulnerable (Tucker et al. 1961).
How to avoid livestock poisoning by fiddleneck and popcorn flower
The best way to prevent livestock poisoning by these forbs is to make sure there is plenty of good forage available. Livestock don't typically seek out fiddleneck or popcorn flower. Fiddleneck and popcorn flower have more stem than leaf, so they aren't very palatable, and they are densely covered in hairs that tend to discourage grazing. In a pasture with plenty of grasses and desirable forbs, then, animals will easily avoid these harmful plants.
The risk of poisoning arises when there is little else for the animals to eat. As a pasture that has been overgrazed or a pasture experiencing a drought therefore might have too few plants for the animals to be able to avoid popcorn flower and fiddleneck. When possible, having more than one pasture can help keep animals safe. Animals should be moved out of pastures where the only available plants may be toxic.
Body size is also a factor in many cases of toxicity. A fully grown 1,000-lb animal may be unaffected by a small amount of these toxins in their diet (such as this horse, pictured above, who ate a mouthful of grass plus a single fiddleneck plant right in front of me), while a young or small animal might become seriously ill after eating just a few plants. Whether an animal develops clinical signs of toxicity or poisoning depends on the concentration of toxin in the forage, the quantity of forage consumed, and the animal's size. However, any amount could be harmful and if you notice your animals are consuming toxic plants, please contact your veterinarian.
Can fiddleneck and popcorn flower be controlled?
You are not likely to eradicate them, but there are ways to control these plants if you are concerned about them.
Both fiddleneck and popcorn flower can be hand-pulled – gloves recommended to protect against the hairs – if present in small patches. On small acreages, mowing an infested pasture before the plants produce seeds in the spring can help reduce the population. Some herbicides can also help kill these plants; generally speaking, you will need to apply herbicides when the plants are young and small, to prevent seed production for the year. Contact your local UCCE office for more specifics if you want to consider chemical treatments.
Long-term, re-seeding bare patches in pastures and ensuring moderate grazing can also help outcompete these species. Because they have relatively small leaves, popcorn flower and fiddleneck rely on plenty of open space and sunshine to grow. As a result, they are less common in pastures that are densely populated by desirable forages that shade smaller plants.
For more on establishing a healthy pasture, even if you have dryland pastures or pastures with animals other than horses, the free guide here is a great place to start: Establishing and Managing Irrigated Pasture for Horses.
If you are concerned that your animals may have been exposed to toxic plants, contact your veterinarian. If you have concerns about plants in your pastures, feel free to contact your local UCCE office for assistance with plant ID.
Check out CalFlora to see the geographic distribution of these and many other plant species in California
Craig, A.M., L.L. Blythe, E.D. Lassen, and M.L. Slizeski. 1985. Resistance of sheep to pyrrolizidine alkaloids. Israel Journal of Veterinary Medicine 42:376-384.
Hartmann, T., C. Theuring, T. Beuerle, L. Ernst, M.S. Singer, and E.A. Bernays. 2004. Acquired and partially de novo synthesized pyrrolizidine alkaloids in two polyphagous arctiids and the alkaloid profiles of their larval food-plants. Journal of Chemical Ecology 30(2):229-254.
Tucker, J.M., D.R. Cordy, L.J. Berry, W.A. Harvey, and T.C. Fuller. 1961. Nitrate Poisoning in Livestock. California Agricultural Experiment Station. Circular 506, 12p.
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CA Avocado Society/CA Avocado Commission/UCCE
August Seminar/Webinar Topic
Life without Glyphosate, Weed ID, and A Review of Microbial Amendments
Click on the Presentations Title for the PowerPoints
by: Ben Faber
by: Sonia Rios
Wednesday, August 12
9 - noon
Avocado Grower Webinar
Weeds and Biostimulants
Sonia Rios (UCCE Farm Advisor, Riverside/San Diego Counties Subtropical Horticulture) will talk about how to identify different weeds and the various methods that can be used to control them. And if glyphosate is lost, what chemical alternatives are available and how would they be used. A look at new products.
Ben Faber (Subtropical Crops Advisor, Ventura/Santa Barbara Counties) will talk about biostimulants in agriculture. What are they? How might they work? How to assess whether they work? There are many different new products brought on to the market every year that purport to improve plant growth and yield, often with lavish claims. Can some of those claims be backed up with solid data? Some can and some can't. How does one decide what is worth trying?
- Author: Chris McDonald
reposted from: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=41400
Stinknet (Oncosiphon piluliferum, aka globe chamomile) is a winter annual that is spreading across Southern California and poses threats to wildlands, rangelands and agricultural areas. Stinknet was first found in western Riverside County in the early 1980's. It slowly spread to surrounding areas and by the late 1990's it was found in over a half dozen locations in Riverside and San Diego Counties. By this time, it had also spread to Phoenix. While stinknet has not been one of the fastest weeds to spread across the state (stinkwort, Dittrichia graveolens, is definitely a top contender for that spot, see here) it is now currently found in every county in Southern California (except Imperial, yet) with the largest infestations in Riverside and San Diego Counties. Stinknet continues to spread north across Los Angeles, the central valley and coast, and east across Arizona, it was also recently found in Las Vegas.
Stinknet is easiest to identify when in flower. At flowering, it grows from several inches to 3 feet tall.
Stinknet in full flower (Image credit: Chris McDonald)
A closeup of stinknet flowers (Image Credit: Chris McDonald)
Stinknet is closely related to the pineapple weeds (Matricaria spp., see here) and brass buttons (Cotula spp. see here and here), and resembles those more common weeds. The main difference is the flower of stinknet is very round, like a globe, (see above) while the flowers of pineapple weed and brass buttons tend to be slightly conical to half a sphere.
Brass buttons (Cotula coronopifilia Image credit: Carol Witham)
Pineapple weed and brass buttons also tend to grow more along the ground, and stinknet grows upright. Another diagnostic feature is that stinknet stinks. All plant parts have an unpleasant turpentine, pine or tar-like smell, and even very small plants have this smell. You can even smell the odor of a large field of stinknet when you are near a very large infestation.
Successful Control Options
Stinknet can be controlled with several herbicides that can be used in wildlands. Milestone (aminopyralid), Capstone (aminopyralid and triclopyr) and glyphosate are all highly effective at controlling stinknet, but only before the plants have flowered. Often if herbicides are applied after flowering, stinknet can finish flowering before the herbicides have killed the plant. Milestone and Capstone also provide season-long control of stinknet with suppression lasting up to and in some cases beyond 12 months. Several researchers, including myself, are working on other control measures and understanding its biology to better help managers control stinknet. Those projects should wrap up in the next year or two.
What doesn't work well at controlling stinknet?
Telar XP (chlorsulfuron) was not effective at controlling stinknet in Southern California. Transline (clopyralid) was inconsistent at controlling stinknet. Transline had shown promise of effective control in relatively dry years, but in other more wet years the treated plants were able to grow out of the treatment. Mechanical removal (mowing or string trimmers) has shown to be of limited effectiveness, mostly because the cut plants resprout and flower closer to the ground. Multiple cuttings close to the ground alleviate this problem and can provide good control, but a simple single cutting is not very effective. Stinkent can grow in dense patches so hand pulling will only work on a very small scale, and multiple sessions are needed. Stinknet is not palatable to livestock, so grazing will not be an effective management strategy and can make the problem worse.
Threats to California Agriculture
In Western Australia, stinknet is a problem weed in small grain crops. In both South Africa (the home range of stinknet) and Austrailia stinknet is a problem weed in rangelands too. This is because stinknet is unpalatable to many livestock. While stinknet is not currently known to be toxic, there are reports it can taint the meat and milk from those animals. If the patterns in Australia and South Africa hold in the US (and so far in a few observed cases it appears to be similar) and if stinknet continues to spread into rangelands and agricultural areas in California, then it will cause problems.
Right now, the best way to keep stinknet from spreading locally in California is to identify early infestations and rapidly respond to those initial infestations. This strategy is called early detection and rapid response (EDRR). Fortunately, the largest stinknet populations are found in only a few locations in Riverside, San Bernardino and San Diego Counties. However, numerous small populations occur across Southern California. I have also noticed that very few stinknet patches decline in size, once stinknet colonizes a site it tends to expand, or even hold its ground during a drought. The areas with the earliest known stinknet populations, in both California and Arizona, now have large, very high-density patches. Those patches can be over a dozen and up to hundreds of acres in extent. Stinknet appears to be a strong competitor especially in disturbed areas, but also in undisturbed wildlands too, and can quickly become the dominant plant. It does this by creating numerous small patches and as those patches grow, they form large blankets carpeting acres or long strips along roads and trails. Stopping those small stinknet patches can prevent them from turning into large infestations.
More information on stinknet will be available as our research progresses and we learn more about its biology, spread and controlling it.