Dodder: A devastating and dreadful parasite
Thursday, July 10th, 2014
Issue 28, Volume 18.
It so distinctly captured my attention that I immediately decided to ask some local invasive plant experts about it. When I asked the knowledgeable folks at Mission Resource Conservation District (MRCD), I was given an answer.
"I believe what you are referring to is called dodder," said Karla Standridge at the MRCD, directing me to a treasure trove of information from the University of California Agricultural Dept.
The bottom line is that dodder (genus Cuscuta) is a parasite, an annual plant that infests crops, ornamentals, native plants, and weeds. Obviously it doesn’t discriminate between those that are the beauties and those which are the beasts.
Lucky for us, dodder is most prevalent in the Americas. Sadly enough, it is in the (very) extended family of the Morning Glory.
While there are some 150 species of dodder, some are inclined to infest alfalfa, weeds, and thistle. Others are found on crops like asparagus, melons, and tomatoes.
Japanese dodder (native to Asia) has found its way into California also. It has been found attacking and covering ornamental shrubs and fruit trees. It apparently favors citrus trees, but also easily latches on to oaks and willows.
At a distance, it looks like a dark gold-colored spider web, but up close you can see the slender, twining stems that vary in color from pale green to yellow or bright orange. It is easy to spot against green foliage or even dry weeds. Some say the Japanese dodder looks like spaghetti noodles. Experts said it rarely flowers but if it does the flowers are small and pale yellow to cream-colored.
Like any parasite, dodder draws its energy from the host plant. (A dodder seedling will die within 10 days without a host.)
Like many vines, dodder continually reattaches to its host and its shoots can spread from host plant to host plant, forming a dense mat of intertwined stems.
Its growth can run rampant, given that each plant is capable of producing several thousand seeds. Fortunately only about five percent of the seed germinates the year following its production, but the bad news is that because of its hard seed coat the rest can remain dormant in the soil for more than 20 years! Of course that can be shortened by negative environmental factors.
In doing this research, I am pretty sure what I have seen in one Fallbrook area - just north of State Route 76 near Old Highway 395 is Japanese Dodder.
Experts said the spread of Japanese Dodder in California is generally not by seed production, but rather by small pieces of its stems being transported and dropped by birds and other wildlife. Pruning and composting practices could also contribute. Evidently when these stem pieces come into contact with a new host plant or tree, they rapidly take off growing. It has been said that Japanese Dodder can grow up to six inches per day.
The damage this parasitic plant causes can range from moderate to severe. It can lead to plant and tree failure and death. Smaller trees are more likely to suffer fatal damage than larger ones. Since dodder draws the life blood/nutrients from the plant/tree, it puts it in a weakened state open to other parasites, diseases, and more.
What can be done about this unwanted plant? Experts have said when it comes to Japanese Dodder, there is no use for a lay person to try and control it.
"This weed is under an eradication program in California and has spread to more than a dozen California counties," it was stated in information from the University of California agriculture dept. "Contact your county agricultural commissioner to receive proper identification and help with control."
Native dodder can be helped by performing damage control. If one suspects a plant or tree on the property is afflicted with dodder, it is important to isolate the parasite.
Therefore, effective management requires control of the current population, prevention of its seed production, and suppression of new seedlings in following years. In a case of severe infestation, it may be best to remove the infested host plants and replant with non-hosts. If you see dodder tendrils reappear, remove the young parasitic plant immediately.
Plants that are not dodder-friendly (non-hosts) include grasses and many other monocots including lilies. Winter plants such as crucifers and legumes and transplanted trees and shrubs (from clean areas) usually are good alternatives.
If a new dodder growth is found on a tree or plant, prune the affected portion of the host plant/tree about one-fourth of an inch below where the dodder is attached, otherwise it can regenerate itself. It is advised to place dodder plants in a plastic bag, and dispose of them in the trash, so as not to infect other areas.
Experts don’t generally recommend using chemical treatments on dodder since it can be controlled by removing, pruning, or replanting. However, pelargonic acid (Scythe) has been found effective, but it also kills any plant tissue it comes in contact with.
To learn more, visit the California Dept. of Food & Agriculture website at www.cdfa.ca.gov (search: dodder) or University of California agriculture information at http://ucipm.ucdavis.edu/PMG/WEEDS/dodder.
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