The number of places where ragwort is found is twice as large as in 1975. Larvae of a beetle are a natural enemy, but patience is a virtue, says Boki Luske of the Louis Bolk Institute.
The biennial poisonous plant ragwort produces many seeds in its second year, which then disperse this herb. A mature plant produces between 75,000 and 200,000 seeds, so the population can expand quickly.
According to researcher Boki Luske of the Louis Bolk Institute, the plant is ecologically valuable. It attracts 180 species of insects, such as butterflies and bees.
Verge management
Partly as a result of the enormous amount of seed produced, the number of plants is increasing. In the past, the herb was sometimes sown for verge management. In addition, it will have the opportunity to visit places where land is returned to nature. There is often no management here.
The plant notices that it is having a hard time and starts flowering earlier
Sjaak Sprangers, organic dairy farmer in Kaatsheuvel
Furthermore, the plant settles in bare spots, for example as a result of grazing and extensification. The plant is recognizable as a rosette the first year. In its second year, it is recognizable by long stems and serrated leaves.
The disadvantage is the toxicity, especially for horses and cattle and to a lesser extent for sheep. The latter have an enzyme in the gastrointestinal tract that partially renders the toxin harmless. That is why sheep are sometimes used to combat the herb.
Feed extraction
This does not apply to horses and cattle. ‘The toxicity is not a problem for horses and cattle in the field. They don’t eat it. This is no longer recognizable after forage harvesting, which means that cattle can die from liver failure,’ says Luske.
‘You can therefore no longer use the clippings anywhere. It is also a cost item. In fact, you can only compost it, so that the seed does not spread further. Another option is to stick out the plants and compost them,’ explains the researcher.
Natural enemy
For the Louis Bolk Institute, this is reason to look for a solution for this herb that is difficult to combat. There is a natural enemy: a small brown beetle, the scallop flea beetle. Successful trials have been carried out with this in New Zealand and the American state of Oregon. Because ragwort is an exotic species in New Zealand, the beetle was imported from Switzerland and Italy.
That beetle lays eggs in the summer at the foot of the ragwort. The following spring the eggs hatch, after which the larvae eat their way up the plant, disrupting the sap flow and preventing the plant from developing further. From June the adult beetles emerge and lay eggs.
Trial
These experiences abroad prompted the Louis Bolk Institute to conduct a trial with this beetle, which occurs naturally in the Dutch dunes, at organic dairy farmer Sjaak Sprangers in Kaatsheuvel in Brabant. In 2010, the beetles were caught near the dunes in Wassenaar.
The thirty beetles were then released on a Sprangers meadow, after which the plot was followed for four years. At the end of this period, the trial did not yield the desired result and was closed.
Remarkable discovery
A few years ago, the organic dairy farmer made a remarkable discovery. The ragwort plants did not develop and started flowering at an early stage. Emergency bloom, the entrepreneur calls this. ‘The plant notices that it is having a hard time and in order to be able to reproduce, the plant starts to flower.’ Other plants turn brown.
When the organic dairy farmer cut through a less healthy plant, he saw that the inside of the stem had been pierced. He also found a larva here. After a long search in the area, he saw the 2 millimeter large beetle, recognizable by its large hind legs.
Distance limited
The beetle can jump with those legs, hence the name ‘flea’. Since the beast cannot fly, the distance is limited. ‘The range is 20 meters in one year’, Sprangers estimates.
That was reason for the entrepreneur to stick out infected plants. Not for the compost heap, but to replant them elsewhere. With this he also spreads the beetle, which multiplies by mating.
Amazing result
In 2023, a few years later, the result in this meadow, where the young cattle are now grazing, is astonishing. Most plants in the meadow turn brown or are somewhat smaller. Plants are still blooming and seeds are still being dispersed sporadically. The larva of the beetle can be found in many affected plants.
Sprangers is satisfied with this result. ‘Various fellow dairy farmers have planted plants here to place on their own plots so that they can multiply here.’
Does this have a future according to the dairy farmer? “It’s good to see this working now. For an effective operation, an entrepreneur should now arise who focuses on propagating this beetle in order to then market it.’
Herb causes irreversible liver damage
The toxic effects of ragwort are due to toxins, which primarily affect the cells of the liver, Royal GD reports. The toxins are in all parts of the plants and remain active in dried plants. When they die on land, the toxins disappear. Ragwort poisoning gives symptoms of liver failure, such as jaundice and sunburn. In addition, deviant behavior such as severe depression, aimless wandering or circling, balance problems and dropout are seen. Symptoms can also be less clear, such as production complaints and weight loss. What is striking about these toxins is that they can have a persistent and long-lasting effect for weeks or in some cases months. This means that symptoms sometimes occur long after admission. That sometimes makes it difficult to link symptoms to eating this herb.
2023-08-25 13:30:00
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