Have you ever walked by a shrub that looked like it was covered with spaghetti? No, it’s not cloudy with a chance of meatballs – the plant is infected with a weed called Dodder. Dodder is a parasitic vine that is extremely difficult to eradicate. What is a parasitic vine? It’s a weed that depends on a host plant for all of its needs.
How to Identify Dodder
To spot Dodder, look for long, slender, thread like stems that kind of look like spaghetti. It may also have bell shaped flowers that are cream colored. Dodder is a tricky weed because it grows and branches out to nearby plants very easily. Because of this ability, it often looks like a matted mess covering up a whole plant. The more vines there are, the more energy that is removed from the host plant. The loss of nutrients to the Dodder combined with the loss of light from the matted weeds can cause major damage to the host plant.
One of the biggest challenges with Dodder is its seeds. Dodder is a flowering plant and its flowers will produce thousands of seeds which, when mature, will fall to the soil below. The seeds have a very hard coat around them and stay dormant in the soil until the right conditions come around to sprout. When it comes to getting rid of a Dodder infestation, it is the seeds that cause the greatest headache, which is why prevention is so important.
At the first sign of Dodder, pull it off the plant and throw it away. Check the infestation site often because the weed may quickly regrow so it’s important to keep pulling. If you see Dodder soon after it has attached itself to a host, prune the infected portion of the host plant 1/8 to 1/4 inch below the point of the attachment, otherwise the dodder can regenerate. If the Dodder is attached to a shrub or tree, pruning is only helpful if it is confined to one or two branches. Removing any more than that will most likely cause major damage to the host shrub or tree.
Because Dodder is extremely difficult to destroy once it has taken over a plant, it is important to try to end the growth cycle. Use a pre-emergent herbicide like oryzaline that, when added to the soil under the infested plants, will kill the seed before it grows. Currently, there are no post-emergent herbicides that kill dodder without also killing the host plant. If the infestation is completely unmanageable, removal of the host plant with its attached dodder may be the easiest solution.
Tamarisk, better known as Saltcedar, is an extremely aggressive and invasive foreign plant. Saltcedar was originally introduced to the United States as an ornamental shrub. Saltcedar grows rapidly and can reach heights of up to 26 feet. The Saltcedar also reproduces quickly; it can flower during its first year and, at maturity, produce 600,000 seeds annually. Its adaptability and resilience to harsh elements allows the Saltcedar to aggressively colonize. All of these traits combine to make an invasive plant.
Recognizing a Saltcedar
Though it looks similar to an evergreen, the Saltcedar is a deciduous tree (or shrub) with small scale-like leaves. Its light pink flowers form dense masses at the top of its long slender branches. The Saltcedar’s fast-growing roots spread deep and wide causing damage to nearby sidewalks and walls. Due to its rapid and successful reproduction, the Saltcedar escapes controlled cultivation easily and germinates in unwanted areas. It also consumes large quantities of water, up to 200 gallons per day, and deposits salt to form a saline crust to prevent other plant life from thriving in its vicinity.
Getting rid of the Saltcedar is no easy feat. It is resistant to fire, flooding and most weed control methods. A Certified Arborist or Arizona Office of Pest Management (OPM) Licensed Pest Applicator can eliminate the Saltcedar by cutting it to the ground and applying an herbicide to the stump. A list of Certified Arborists can be found at http://www.treecareindustry.org/index.aspx and Licensed Pest Applicators can be found by visiting the OPM website, http://www.sb.state.az.us/EmployeeDir.php.
Is It Grass?
Possibly one of the worst turf weeds to infest your lawn, Nutsedge spreads quickly and is extremely hard to eradicate. Nutsedge is the common name for Cyperus esculentus (yellow) and Cyperus rotundus (purple), a weed type that germinates well in warm moist soils and spreads through tubers (referred to as “nuts” or “nutlets”) under the soil. The tubers, or nuts, are grown on underground stems known as rhizomes that can grow as deep as 12 to 16 inches under the surface of the soil bed. Buds sprout on the tubers and grow new plants, this process eventually leads to a patch of Nutsedge.
Nutsedge looks similar to grass, but the blades are thicker and stiffer than most grasses. They grow straighter and in sets of 3 stems at the base (as opposed to 2 in grasses).
An infestation of Nutsedge is problematic because it grows twice as fast as turf grass requiring more frequent mowing and it is lighter green resulting in non-uniform turf appearance.
Nutsedge is nearly impossible to get rid of, but it can be controlled. If you are lucky and catch the Nutsedge early you can limit the production of tubers, which will suppress it from spreading. To limit tuber production continually remove the shoots and as much of the plant as possible by hand every 2 weeks. This will cause the plant to put all of its energy into growing new shoots instead of new tubers. Mature tubers can re-grow their shoots up to 12 times, so you will need to be consistent.Since Nutsedge looks similar to grass it is difficult to recognize early. If it has already taken over a small portion of your lawn you may want to consider chemical treatment. The best herbicide to treat Nutsedge is called Sedge Hammer, which is very expensive and can only be applied by a Certified Spray Technician (AZ SPCC Certified). The chemical should be applied during the growing season every 3 weeks; it will take as many as 3 or more applications to fully control the Nutsedge. To find a company with Certified Spray Technicians visit http://www.sb.state.az.us/CompanyDirectory.php.
A Troublesome Weed
Euphorbia supina, or prostrate spurge, is a low-growing weed that forms a dense mat often found under other plants. Spurge is native to the United States and has a shallow taproot and stems that exude a milky white sap. Spurge leaves are small, opposite each other on the stems, green or red and often have purple spots. This weed germinates and thrives in dry, hot climates and tolerates some shade, but prefers direct sunlight. Like any other opportunistic weed, it takes advantage of disturbed soils or stressed turf areas.
Spurge is a late-germinating, summer annual with small and inconspicuous flowers. Spurge blooms anytime between the months of June and October. A single spurge plant is capable of producing thousands of seeds each flowering cycle.
Control Without Chemicals
Because spurge has a relatively shallow taproot, it is easy to remove manually from granite areas and planters. Infested turf areas are more difficult to control manually simply because young spurge plants are hard to spot among blades of grass. The best way to deter spurge in turf is to encourage turf density through proper watering and fertilization.
Control With Chemicals
Spraying spurge with an herbicide is the easiest way to control this troublesome weed in turf areas. However, you have to use the correct herbicide in the correct landscape area. Roundup is safe and widely available at any home improvement store; however, Roundup can only be sprayed on spurge in granite areas. Simply follow the instructions on the label making sure not to spray Roundup on spurge growing in turf. Roundup is a nonselective systemic killer, which means plants or grasses absorb the chemical into their root system and the chemical cannot differentiate between plants you want and weeds.
To kill spurge growing in turf areas, use an herbicide that targets broadleaf weeds, such as Amine 4. These types of herbicides can only be applied by an Arizona Office of Pest Management Licensed Pest Applicator. To find a company with a Licensed Applicators, visit http://www.sb.state.az.us/EmployeeDir.php.
There is a Fungus Among Us
You may have noticed brown clusters growing on your Catclaw Acacia trees. Known as Catclaw rust, the fungus infects the terminal ends of branches and causes a distorted, bunchy growth. It produces spores on the leaves of the tree in the late spring and summer that eventually cluster together and appear dark brown in color. Unfortunately, the cooler temperatures throughout May and the beginning of June were ideal conditions for the fungus. The monsoon season brought higher levels of humidity, yet low levels of rainfall this year, allowing the fungal spores to spread readily and rapidly.
Is There a Treatment for the Fungus?
According to Dr. Mary Olsen, Plant Pathology Extension Specialist at the University of Arizona, there is no known effective and practical treatment for Catclaw rust. The fungus is a normal occurrence in nature and prompts a “survival of the fittest” environment among the trees. The fungus typically has a two year life cycle from the start of each new spore growth. Under favorable conditions, the outbreak could be similar next year.
Removal or branch pruning of the Catclaw Acacia is not advisable at this time. Eliminating the affected branches may further weaken the tree by creating an open wound during the growing season. Furthermore, the fungal spore can be easily spread through pruners and disseminated in air currents.
What Can You Do?
The good news is that the less-than desirable brown clusters can be removed when the tree is in dormancy (December through the end of February). Here are some guidelines for removing the brown clusters:
- Infected branches should be cut off from the union of two branches only when the tree is dormant.
- Do not cut in the middle of the branch or the fungus is likely to growth back.
- Remember that it will take two years for the fungus to “run its course.” Fungus that appears next spring may take another 2 years to dissipate.
- Trees that are completely infested should be removed from the landscape.
- Continue to monitor your trees and have patience.
It is expected that most trees, unless heavily infested, will recover. For more information visit the University of Arizona Plant Pathology Extension website:
As great as the rains have been for plants and turf, they’ve also been good for one other thing. Weeds love rain! It’s during springtime that weeds grow the fastest and, without control, can dominate decomposed granite (DG) and other areas.
THE GOOD NEWS?
If we’re at your Community, we’ve got you covered. DLC already has a comprehensive weed control program in place, using pre and post emergent products. For those few weeds that do pop up, we treat them in their early stages so they’re a non-issue.
QUICK TIP: If you’re currently battling with weeds in your Community, you might review your landscape providers’ plan.
ADDITIONAL RESOURCES: To learn more about weed control for homeowners, click here.
Soaking rains bring much needed water to our desert environment, including plants. Rainwater is especially beneficial to plant material as rainwater is less alkaline than our irrigation water. While rain is a positive thing for our plants and irrigation water bills, it also helps weeds grow. For effective weed control in your yard, manual removal is the easiest way to get rid of a small number of weeds. To control weeds over a large area, herbicides are the most efficient tools available. There are two categories of herbicides for weed control: Pre-emergent and Post-emergent.
Pre-emergent herbicides are designed to prevent seeds from germinating in the soil. They are most effective when applied during the rainy season. In Arizona, that means either before the summer monsoon in June & July and from October through January to take advantage of the winter rains. A timely application of pre-emergent can greatly reduce the number of weeds that germinate since it inhibits the weeds’ roots and does not allow them to grow.
Post-emergent for winter and spring weeds:
Post-emergent herbicides kill weeds that have germinated and are visible in the landscape. To kill weeds in winter months, you need to use a herbicide containing Diquat.
Spectracide products, which contain Diquat, are available for personal use at most home improvement stores or nurseries.
Post-emergent for summer weeds:
Spring and summer are the best times to use Roundup concentrate. Be careful not to spray weed killer on plants or turf as the weed chemical is absorbed by the leaves and travels through the plant. These products cannot differentiate between plants and weeds. Additionally, this type of weed killer does not instantly kill the plant. If you spray the weed and then remove it, any remaining roots may not have time to absorb the weed control spray.
*Product label design and prices may vary. These products are Environmental Protection Agency (EPA) approved and have been deemed safe and reliable. No license is needed to apply most herbicides on your own property. DLC trains and maintains a crew of applicators to safely transport and apply these herbicides in your common areas. Our spray applicators are Licensed Pest Applicators by the State of Arizona Office of Pest Management. When dealing with any chemical, make sure to read the label and follow instructions carefully.