I have the parasite dodder in my ivy. What do I do? Can this be killed by freezing? Is there a chemical that would kill it without killing the ivy?
So far, nurseries have suggested that I cut the ivy down to the roots and use a pre-emergent. One nursery recommends Ronstar G. A website recommends Dacthal. Do I use the pre-emergent now? Or do I wait until spring?
I am told you are the best authority, and I really want your wisdom and recommendations. Please provide recommended procedures and brand or chemical names or any or all products.
So far, I have just pulled off the dodder to try to reduce its spreading until I get your recommendations.
– Melvin Welch, Fair Oaks
Dodder can be a real pain, according to UC Cooperative Extension master gardeners. Nicknamed “devil’s hair,” “devil’s guts” and “strangleweed,” this odd parasite looks like yellow-green or sometimes gold-orange thin spaghetti. It tightly wraps around its host plant and can eventually kill the host while robbing it of nutrients.
According to University of California research, dodder attacks a wide range of ornamentals including English ivy as well as chrysanthemums, impatiens, morning glory, periwinkle and petunias plus many herbs and vegetables.
Japanese dodder, which recently invaded California, is fond of shrubs and fruit trees, particularly citrus. Considered a noxious weed, Japanese dodder can quickly overwhelm and kill shrubs and small trees.
First, you need to determine what kind of dodder is in your ivy. More than 50 species are native to the United States. Several have scalelike leaves, 1/16th of an inch long. But if you have leafless Japanese dodder ( Cuscuta japonica), you need special help.
If you believe you have Japanese dodder in your ivy, do not try to control it yourself, stresses the UC Davis’ integrated pest management (IPM) program. This weed is under an eradication program in California and has spread to more than a dozen California counties including Alameda, Butte, Contra Costa, Fresno, Los Angeles, Merced, Sacramento, Shasta, Solano, Sutter, Tulare, Yolo and Yuba. Contact your county agricultural commissioner to receive proper identification and help with control. More information is available on the California Department of Food and Agriculture website and at the UC’s IPM website listed below.
Controlling native dodder takes great effort and usually several years to eliminate an infestation completely. Frost will kill the dodder (which grows as an annual), but not the seeds. You will need to cut your ivy down to the ground as close as possible and apply a pre-emergent. Do this in the early spring before the dodder sprouts again. Ronstar G works primarily on broadleaf weeds, which makes it ineffective on dodder. Dacthal can be effective against dodder but is highly toxic to fish and can harm bees and not recommended for home gardeners.
The UC IPM program recommends the pre-emergent trifluralin (sold under such brand names as Snapshot and Treflan) for dodder control. It should be applied in early spring before new dodder seedlings can sprout.
When removing dodder, dispose of the whole plant and any infected material in the trash – don’t put it in green waste containers or the compost bin. If the plant is not properly destroyed, it can easily spread through compost or mulch. Pull up any seedlings as they appear before they can attach to a host plant.
To learn more about dodder, check out the IPM Pest Note 7496 online at www.ipm.ucdavis.edu. Or get a copy by mail. Send a stamped, self-addressed business-size envelope to: Pest Note 7496 Dodder, UC Cooperative Extension, 4145 Branch Center Road, Sacramento CA 95827.