Invasive Pest Spotlight: Pampasgrass & Jubatagrass

The invasive pest spotlight focuses on emerging or potential invasive pests in California. In this issue, we cover the invasive plants pampasgrass and jubatagrass.

Pampasgrass & jubatagrass facts

Pampasgrass (Figure 1, top) is a common ornamental fland­scape plant that readily naturalizes throughout California's coastal areas and some interior regions. Historically, pam­pasgrass was planted for erosion control, but it has since escaped cultivation and spread along sandy, moist ditch banks throughout coastal regions of southern California. Pampagrass can also grow in the hot, dry climate of inland areas of California.

A similar-looking invasive grass, jubatagrass (Figure 1, bottom) is more widespread and aggressive and is a major pest in coastal redwood forest areas. Jubatagrass thrives in cool, fog­gy environments and does not tolerate temperature extremes or drought.

Both pampasgrass and jubatagrass outcompete native plants; a single floral plume can make 100,000 seeds in a year. They create fire hazards with excessive build-up of dry leaves, leaf bases, and flowering stalks. The tough leaves have serrated edges that can easily cut skin.

What can you do?

Plant other ornamental grasses in your garden or landscape. Many species including native grasses can be planted that resemble pampasgrass but aren't problematic. This includes several species of Muhlenbergia: deer grass, white awn muhly, and Lindheimer's muhly. California native Pacific reedgrass grows well on the coast and is deer resistant. For a large, tough bunchgrass, try giant sacaton, a native of the Southwest. Giant wildrye, another California native, will grow into dense stands that attract birds.

For more information, see the University of California Weed Research and Information Center fact sheet at http://wric.ucdavis.edu/PDFs/pampasgrass%20and%20jubatagrass%20WRIC%20leaflet%2099-1.pdf.

 

Original source: UC IPM Home & Garden Pest Newsletter (Spring 2022) issue.

Belinda Messenger-Sikes is the Urban IPM Writer and Editor for the UC Statewide IPM Program. You can contact her at bmsikes@ucanr.edu.

 

Stinknet (Oncosiphon pilulifer) is a relatively new weed to North America and has been moving quickly and spreading in San Bernardino County. Gardeners may have noticed this unusual yellow-flowered plant growing in their yard this year, even though we are in a significant drought. This is a sign of how invasive this weed can be. It would be very wise to remove this plant from your yard and ensure it does not grow in your community.

Stinknet was first discovered in North America in Riverside County in the early 1980's and began to spread shortly thereafter. In the 1990's, it began to spread much more quickly and within 20 years of its discovery, it was found in multiple locations in Riverside and San Diego Counties as well as in central Arizona. Stinknet is a winter annual germinating with the fall and winter rains, blooming in the spring, and usually dying in the summer. However, stinknet seeds in the soil can germinate multiple times a year creating multiple cohorts and making it that much more difficult to remove.

 

Identification of stinknet:

There are four characteristics you can use to help identify stinknet. Each one by itself may or may not be helpful, and when combined they will help you correctly identify stinknet. 

First, and easiest to identify, is the inflorescence is bright yellow and round, almost globe shaped. The bright flowers dry to a dark brown color and tend to hold on to their seeds for many months after the plants die into the summer.

 

Second stinknet, like the common name suggests, stinks. It has a strong odor which many people find unpleasant, a strong resin, turpentine, pungent pine-like odor. Similar weeds which have a round inflorescence do not have an unpleasant odor (pineapple weed has a pleasant pineapple-like odor).

Third, the leaves of stinknet are finely divided. They are doubly pinnate (bipinnate), meaning the leaves are divided at least two times into smaller divisions. While many plants have this characteristic, this can be useful if your unknown plant is not flowering, has doubly divided leaves and you can smell it. 

 

Last, stinknet germinates in the fall and winter rains, grows as a small rosette through the winter and then starts to bolt and flower in the late winter through spring. In places that receive irrigation or in moist soils, stinknet can flower even longer from the early spring through the summer. 

While size can be helpful for some plants, the size of stinknet can be highly variable. Stinknet growing in poor conditions can grow to be only 6 inches tall with a few flowers. In good condition it grows to be almost 3 feet tall with hundreds of flowers and appears almost shrub like.

 

Local Infestations:

San Bernardino County so far has very few large stinknet infestations, but many scattered infestations. However, this year I've noticed more and more individuals and patches of stinknet in San Bernardino County, many of which will eventually become large infestations, if left to spread.

There are very large infestations in parts of Riverside (see below) and San Diego Counties and Phoenix where stinknet has been invading the longest. In these areas, stinknet covers entire fields and roadsides, covering dozens to hundreds of acres in large patches. There have been very few places in Southern California where stinknet has not continued to spread when left unchecked.

Stinknet is a generalist and can grow in many different types of habitats including wildlands, gardens, suburban landscapes, disturbed areas such as adjacent to roadsides and parking lots, and on hiking trails. It is spreading in San Bernardino County and should thrive in the desert, inland, and at least to 4,000 ft. in elevation in the mountains, and possibly higher. If you do find this plant, report it in the iNaturalist or CalFlora apps. 

 

 

Stinknet grows very well in Phoenix where winter rainfall is less than what we receive in the San Bernardino County deserts. Unfortunately, stinknet flowers every year in Southern California, even when we are in serious drought conditions, allowing it to spread farther each year.

Stinknet is one good example of why gardeners should be wary of new plants showing up in their garden. If you didn't plant it, it is likely a weed. Unfortunately, it will take at least 3 years of weeding to remove stinknet from an established site, so keep up the work and you can rid this plant from your garden and neighborhood.

Producers experiencing this damage may be eligible for assistance.

Crane flies, Tipula oleracea, are once again present on Sonoma and Marin County's range, pasture and cultivated lands this season. I have seen their presence only 3 times during my career, but when in large numbers, the done significant damage. The seasonably warm, average 68 degrees, November, followed by a December that lack proper chilling days, resulting in the survival of excessive Crane fly larvae. Weather conditions have led to current infestations on range, pasture and cultivated lands. Larvae are usually killed when a hard frost occurs during the winter season. During this season, we did not experience an adequate frost to kill the larvae; resulting in a large larvae survival.

Larvae winter in the soil, and when the weather warms, they resume feeding (and damaging fields).

Crane flies, sometimes referred to mosquito hawks, lay their eggs pastures or cultivated lands (silage); these eggs hatch into small, brown, wormlike larvae that have very tough skin, sometimes referred to as” leatherjackets”. The crane fly goes through a metamorphosis or changes body types during its lifecycle that lasts approximately one year. From the time the female lays her eggs until they reach adulthood, the fly changes from a larva to a pupa, then to an adult. Each cycle serves a specific purpose for growth and development of the crane fly. As larvae continues to feed on roots, crowns, and aboveground portions of plants, damage becomes more noticeable in March and April. The damage appears as large dying patches of grass (Figure 1).

Larvae are consuming forage at an alarming rate. During the day larvae mostly stay underground but on damp, warm nights they come to the surface to feed above ground parts of many plants. The larvae vary in size, but at maturity are 1 to 1 ½ inches long. Producers are reporting many areas, completely denuded of forage. In areas affect, there 100% loss.  Around mid-May, larvae wriggle to the surface and the adults emerge; there is one generation a year. The larvae are the damaging stage of this pest (Figure 2).  

"This is why we need Cooperative Extension; they came out to assess the damage to our silage field and quickly determined the cause of the problem. They provided assistance and support to reduce the impact of our forage losses."  Jennifer Beretta, Beretta Family Organic Dairy.

Identify

To determine if these patches are from larvae infestations, dig at the edge of bare ground and grass, 1-2 inches below the surface, larvae will usually be found at the base of the vegetative layer (thatch) or in the soil just beneath the plants. They will be anywhere from ½ to 1 inches in length. 

Control

Control options are limited, especially if the land is under organic production. Beneficial nematodes can be spread on the land to reduce the larvae infestations. Unfortunately, this method results in only 50% control. Organic sprays can also be used, but their efficacy has not be researched in California. Discing bare ground might expose larvae to predators such as birds and predaceous ground beetles and other natural causes. The use of chickens might also be effective if they are able to scratch the ground to get the larvae.

Bare patches of ground can be seeded, if done early. Given it is so late in the growing season, reseeding with annual species, to prevent weed infestations or soil erosion, will be the best option. You can graze the silage crop in order to recoup forage losses.

Assistance

All affected producers should contact the Farm Service Agency, Cecilia Medina, ana.medina@usda.gov, 707-644-8593, on programs for forage losses. The Emergency Livestock Assistance Program (ELAP), is available to producers when forage losses can be attributed to weather up to 180 days per year. Weather is the cause for the infestation of Tipula oleracea infestation (see table below).  Contact Cecilia as soon as possible; she can assist in filing a notice of loss. Their office is located at 1301 Redwood Way, Petaluma.

January 2020	Avg. Temps 58/37| Rainfall total of 1.94 (Santa Rosa, CA)
December 2019	Avg. Temps 57/42 | Rainfall total of 7.01 (Santa Rosa, CA)
November 2019	Avg. Temps 68/36 | Rainfall total of 1.47 (Santa Rosa, CA) Another Frost Warning was issued on Thanksgiving night: https://www.pressdemocrat.com/news/local/10387442-181/freeze-warning-issued-for-north?sba=AAS
October 2019	On October 30, 2019 a Frost Advisory was issued in Sonoma County; https://www.pressdemocrat.com/news/10240107-181/frost-advisory-issued-as-parts?sba=AAS

If you are under organic certification, contact your local certifier. They need to know that you are experiencing a forage loss emergency. 

If you need additional assistance, field visit or support letter of loss from UCCE, please contact me, at slarson@ucanr.edu or Randi Black, rablack@ucanr.edu

Additional Information

UC IPM Crane Fly Fact Sheet

From the Topics in the Subtropics blog :: March 4, 2020