Dodder weed control and management is of paramount importance to many commercial crop growers. A parasitic annual weed, dodder (Cuscuta species) afflicts many crops, ornamentals, and native plants virtually decimating them. How to get rid of dodder is an ongoing quest for the commercial farmer and may be of interest to the home gardener as well.
Dodder Plant Info
Dodder weed has thin, twining stems either pale green, yellow, or bright orange in color. It is either leafless or with tiny, triangular leaves. The weed bares cream colored bell-shaped blooms containing a seed capsule with 2-3 seeds.
The rootless seedlings have a limited ability to photosynthesize and rely on the host plant to provide them with energy. A dodder seedling can live 5-10 days without a host, but will soon die. As the dodder weed grows, it continually reattaches itself to its host and sends out shoots to attach to nearby hosts as well creating a dense mass of intertwined stems.
Seeds are generally dispersed via the movement of soil and equipment or in dirt clinging to shoes and tires, or in infested plant material that is being transported. The seed germinates at or near the soil surface in the spring when temps reach 60 degrees F. (15 C). Upon emergence, the seedling is dependent upon carbohydrates stored in the seed until they attach to a host. Once attached, dodder plant extracts nutrients and water from the host, predisposing the host to disease and insect invasion, affecting fruit set, and yield and even killing off the host.
Dodder Weed Control
As previously mentioned, dodder is a parasitic weed. It emerges as a rootless shoot that must attach itself to a host within a few days. It embeds its suckers, or haustoria, into the stem of the host plant, literally sucking the life out of the host. If left unchecked, dodder can form large colonies of several feet across and wipe out such crops as:
Dodder is in the Cuscutaceae family, although it is sometimes included in the family Convolulaceae or morning glory family. More than 150 species of dodder occur across the globe, but it is most prevalent in the Americas. With such variety, it can be found in almost any landscape, including salty marshes, mud flats or ponds. Some species thrive in weed fields living off of such plants as bindweed, lambsquarters, and pigweed.
Japanese dodder, C. japonica, a native of Asia, has recently been found parasitizing California citrus groves, along with ornamental shrubs, annuals, perennials, and native oaks, and willows.
How to Get Rid of Dodder
If you live in California where the invasive Japanese dodder has infiltrated itself, you need to contact your county agricultural commissioner or local extension office for assistance in identification and help with control. The rapid spread of this weed has it under an eradication program in California.
Otherwise, you are most likely dealing with native dodder weed and efforts to control this weed require a systematic approach involving multiple methods. Dodder weed control requires immediate attention before the invasion is out of control. Dodder control methods will incorporate control of the current populations, prevention of seed production and suppression of new seedlings.
You can also remove host plants and replant with those plants proven to be inhospitable to dodder weed such as grasses, lilies, crucifers, legumes, or transplanted trees or shrubs.
Remove small infestations of dodder by hand and manage large ones with mowing, pruning, burning or spraying herbicides to thwart seed production. Prune host plants 1/8 to 14 inch (0.5-35.5 cm.) below the point of attachment. Be mindful of equipment and clothing when moving from infested to uninfected areas, as the seeds may cling to them and be transported.
Chemical control is not usually necessary for dodder management in the home garden. Hand removal and pruning are usually sufficient to control the weed. In areas of large infestations, a pre-emergent herbicide may be used followed up by close mowing, burning or spot removal of afflicted host plants.
Dodder -- A Weed That Relies on Others
This past week I received several inquiries about dodder control and so, felt this would be an appropriate time to describe this plant and how to control it.
Dodder or strangle-weed is an annual parasitic plant. There are 8 species found in Iowa. All are native, separated only by subtle flower and fruit differences. Because it lacks chlorophyll, the plant is a yellowish color. The lack of chlorophyll also means it cannot produce any food, thus it produces small suckers that attach to a host plant in order to take what nutrition (food) it needs for growth. It appears to be a stringy mess because of its narrow, twining stems and leaves that have been reduced to thread- like scales. Numerous, compact, white flowers appear in late summer. The 2-celled fruit capsules burst open to release 2 to 4 seeds, which is the only way the plant reestablishes itself each year. Seeds germinate on the soil surface in early spring. The resulting plant is a 2 - 4 inch long thread-like plant with a small root system. Once this plant attaches itself to a (host) plant the root system disappears and the dodder becomes completely dependent on its host.
Unfortunately, there is little that can be done once this plant has wrapped itself around its host plant, especially if its your prized flower or some other desirable ornamental or herb. Pulling the dodder from its host is often futile and usually results in the stripping of the green leaves, branches, and stem tips of the ornamental. However, if you want to prevent seed production, this type of control is necessary and must be done early (before flowering).
Chemical control is extremely limited because of dodder's parasitic nature. Only Dacthal is labeled for the preemergence control of dodder. This herbicide is labeled for weed control with a number of woody and herbaceous ornamental species, but there are some sensitive species (i.e. pansy), so make sure you read and follow the label before making an application. Note: this article was written in 1992. Dacthal may no longer be available.
Dodder seeds are fairly long-lived in the soil, so do not expect elimination of this weed in one year, unless you prevent seed production the first year it infests an area. A few weeds in a landscape is often tolerated, but if it's one like dodder, relying on your ornamentals for food, it needs to be controlled.
This article originally appeared in the August 12, 1992 issue, pp. 138-139.
Texas Plant Disease Diagnostic Lab
SCIENTIFIC NAME of causal agent: Cuscuta sp.
Dodder is a term used to describe a parasitic plant in the genus Cuscuta. Dodder effects a wide range of host plants including broadleaf crops, ornamentals and weeds and some monocots. Cuscuta vines have a distinctive appearance of thin stems with small, indistinct leaves wrapping themselves around their host. Often in summer and early autumn, yellow vines will produce small fruit with the same color as the stem. Infected plants exhibit reduced vigor, growth, and crop yield.
Cuscuta is a genus of obligate, non-species specific parasitic plants with about 170 species primarily found in temperate and tropical regions. Cuscuta infects its host by extracting photosynthates and water through haustorium penetration into the hosts tissue and vascular system. Cuscuta are very poor producers of chlorophyll, making them largely dependent on host plants for nutrients. Cuscuta begin their life cycle as seeds, germinating on or near the surface of the soil during warmer seasons. Cuscuta grows as a rootless, threadlike stem in the direction of a viable host using thigmotrophic and chemosensory guidance. The seedling can produce only minor levels of chlorophyll requiring them to find a suitable host within 3-5 days before dying. After establishing itself on a host, Cuscuta will disassociate with the soil and live entirely on its host. Host interaction initiates the production of a haustorium which penetrates the host tissue and differentiates in the host xylem and phloem. Cuscuta can spread by growing onto nearby plants or through seed production in their fruit.
Avoidance and prevention are the most cost-efficient methods to control dodder infestation. Equipment should be thoroughly cleaned after use in dodder infected field. Cuscuta are most common spread through commercial means by incorporation into crop seed supply. Management of infestation can be as simple as manual removal of Cuscuta from plants when infection is confined to small areas. However, Cuscuta seeds can remain viable in the ground for over 20 years. It is best to remove Cuscuta quickly before vines begin to produce seeds. Alternative approaches require the use of selective herbicide. Preemergence herbicides have been effective in reducing early Cuscuta growth and decreasing host establishment. Pronamide is a benzamide herbicide that has shown to be successful in control Cuscuta in alfalfa when applied prior to emergence. Post emergence methods involve using contact herbicides, such as paraquat or diquat, on both Cuscuta and host.
This factsheet is authored by Brendan Mormile (PhD student)
Dr. Appel’s 2017 Fall PLPA601 students
Factsheet information for the plant health issues represented by the images on the 2018 TPDDL calendar were written by graduate students enrolled in the Department of Plant Pathology & Microbiology PLPA601 Introductory Plant Pathology course in the 2017 Fall semester (course instructor: Dr. David Appel). This exercise provides an opportunity for a high impact learning activity where the students are tasked with producing an informational output directed to the general public and to provide opportunity for the students to write.
Greater swinecress is a winter or summer annual, and sometimes biennial, broadleaf weed. It is a major problem in onion and garlic production in the low desert. Most herbicides registered for onion and garlic do not control swinecress especially in the Imperial Valley. Bromoxynil partially controls swinecress.
Littleseed canarygrass is a winter annual grass weed has become more of a problem in the low desert in recent years. It has become resistant to many herbicides that are selective to grasses, including clethodim and fluazifop. Napropamide, pendimethalin, and glyphosate control canarygrass. Canarygrass can also be managed by rotating to a crop (such as broccoli) for which other registered herbicides (such as trifluralin) are effective options.
UC IPM Pest Management Guidelines: Onion and Garlic
UC ANR Publication 3453
Dodder Control Methods - Learn About Dodder Management In Landscapes - garden
Giant Asian Dodder: A New Invasive Plant Detected in Texas
By Kim Camilli, Texas Forest Service, Oak Wilt Coordinator, Austin, TX 78761 - 7/23/2002
from Texas Forest Service web site at http://txforestservice.tamu.edu/shared/ article.asp?DocumentID=370&mc=urban
An exotic parasitic plant known as giant Asian dodder has recently been introduced into Texas and threatens a variety of trees and landscape plants in Houston. Giant Asian dodder (Cuscuta japonica Choisy) is often cultivated in Asia for medicinal products and may have been intentionally introduced into Houston for similar purposes. The problem is that it has recently escaped and invaded street trees and landscape plants in several Houston neighborhoods. First detected by City of Houston crews in August 2001, dodder has since been found in half a dozen neighborhoods, primarily in southern residential districts of the city.
Giant Asian dodder is a yellow-green vine that resembles spaghetti. It is able to parasitize a wide range of hosts including many agricultural crops (alfalfa, tomatoes, and onions, among others). Giant Asian dodder has been observed parastizing 20 host plants in southern Texas ranging from herbaceous plants to woody ornamentals (such as live oak, crape myrtle and Ligustrum).
Dodder is usually considered an annual plant, but in Texas, especially in the southern regions, dodder is believed to survive for more than one year. Dodder plants are hardy to a temperature of 9 o F. Temperatures below 9 o F will effectively kill the dodder plant. Temperatures in southern Texas rarely reach 9 o F, though frosts do occur. When these frosts take place, the exposed foliage of the dodder plants is affected, but the entire plant is not killed. As a result, it will be able to continue to grow and parasitize its host when warm weather returns.
Dodder is yellow in color and lacks chlorophyll, thus it requires a living host in order of obtain the nutrients needed for survival. The dodder plant obtains nutrients from the host plant by producing specialized structures called haustoria, which attach themselves to the host plant. The dodder withdraws sugars, amino acids and certain nutrients from the host at the site of contact. This parasitic action drains the host of vital resources needed for healthy growth and may weaken and eventually kill it.
Giant Asian dodder grows at a rate of 6 inches per day and can rapidly spread from one infected plant to another nearby host. It can spread to a new area by two other methods. One method of spread involves seed production. In the spring, the dodder plant produces flowers and, if fertilized (usually by self fertilization or, rarely, by wasps or other insects), the flowers yield an abundant amount of seed.
Giant Asian dodder seeds are the size of coffee grains and have thick seed coats that are impermeable to oxygen and water. This allows the seed to remain viable until suitable conditions are present for germination. Dodder seed can remain viable in the soil for a period of 10-20 years. Usually most seed that is produced will germinate the following year.
Dodder seedlings have been reported to emerge from depths of 4 inches in the soil, although usually most seedlings originate from seeds located at a depth of ½ inch or less. Once the dodder seeds germinate, a rootless and leafless seedling is produced. The seedling absorbs water initially from the soil, in a manner similar to a root. The seedling uses the soil as an anchoring point for finding a nearby host to parasitize. Giant Asian dodder seedlings can survive for a period of several weeks without a host plant. In this time period, the seedling extends in length and rotates counterclockwise, seeking a host for a source of nutrients and water. If the seedling does not find a host within a few weeks, it dies.
The second method of overland spread is by fragmentation. This occurs when sections of the dodder vine itself are removed from the main plant and become established on another host. Haustoria are produced from these fragments, establish a connection to the host to obtain necessary nutrients, and continue to grow.
The methods used to control or eradicate dodder consist of post-emergence herbicides, pre-emergence herbicides, injected herbicides, roguing, and eradicative pruning.
- Pre-emergent herbicides are used to prevent dodder seeds from germinating and seedlings from parasitizing available host plants.
- Post-emergent herbicides may be used in conjunction with roguing infected plants, removing host material, and eradicative pruning. The post-emergent herbicides effectively kill the dodder in place, so the potential for spread of the parasite during host plant removal and transport is minimized. When utilizing eradicative pruning, such as in managed landscapes, a barrier treatment should be implemented as well. When possible, remove plants that are within 10 feet of the dodder -infected plants in order to create a host free barrier.
- Herbicides injected into infected host plants are used in some locations when large trees are being attacked by the dodder or other unique difficulties are posed in safely dealing with the disease. A large tree will increase the likelihood of fragmentation and dispersal of the parasite while the host is being felled and cut for transport. Therefore, trees injected with systemic herbicides will rapidly kill the tree and the attached parasite.
Dodder (Cuscuta spp.) is a parasitic weed that infects a wide range of herbaceous and woody plant material. There are approximately 12 species of dodder and each species has a different host range. Dodder is generally brought into ornamental planting via infected plant material.
Dodder is a rootless, leafless, parasitic flowering plant. It is in the morning glory (Convolvulaceae) family. Dodder flowers and produces seed like any other flowering plant. Seeds can remain dormant in the soils for years before germinating. Under the right conditions, dodder seed will germinate, sending up a tendril that attaches to a suitable host plant. If no suitable host is available, the plant will die within a few days. Dodder attaches itself to the host plant’s vascular system with a peg-like haustoria. Once attached, the root system of the dodder plant shrivels and the plant feeds off the host. Dodder contains no green tissues because it does not need to photosynthesize and produce its own food. The stem color of dodder is generally yellow to orange, but can also be shades of red or white. Flowers are small, white or pink, and usually born in clusters.
Dodder infects a wide range of plants, including plants in the Asteraceae family (chrysanthemums, marigolds and sunflowers), Fabaceae family (alfalfa, clovers, soybeans and vetches), and the Ericaceae family (azaleas and rhododendrons).
Remove all plants or portions of plants infected by dodder. Ideally it should be removed before the dodder flowers and produces seed. To date, dodder cannot be controlled through a selective post emergent herbicide application. However if the host plant is killed, the dodder plant will also die. Dodder seed can be controlled with pre emergent herbicides (check label to see if these herbicides are safe to host ornamentals) and soil sterilization.
It is the responsibility of the pesticide user to observe all directions, restrictions and precautions on pesticide labels. It is dangerous, wasteful and illegal to do otherwise. Store all pesticides in original containers with labels intact and behind locked doors. Use pesticides at correct label dosage and intervals to avoid illegal residues or injury to plants and animals. Use pesticides carefully to avoid drift or contamination of non- target areas. Surplus pesticides and containers should be disposed of in accordance with label instructions so contamination of water and other hazards will not result. Follow directions on the pesticide label regarding restrictions as required by State or Federal Laws and Regulations. Avoid any action that may threaten an endangered species or its habitat.
KEEP PESTICIDES OUT OF THE REACH OF CHILDREN!
Pest Alert – Dodder, a Parasitic Plant
Dodders are parasitic plants in the morning glory family. Dodders do not have chlorophyll and must obtain all of their nutrients, water, and carbohydrates by attaching themselves to other green plants. The strands drape themselves over the plant.
These plants have string-like vining stems that look to be leafless. They do have leaves but they are tiny scales. The flowers are small, bell-shaped, and range from yellow to white. They emerge in clusters from summer to fall. Each flower produces one to four seeds. Dodder produces small, pea-like fruit.
Control on woody ornamentals in the home garden is to simply prune out the parasitized branches. In severe infestations, gardeners sometimes must remove the entire infected plants before dodder goes to seed.