Leafy Spurge Spreading in New Mexico; Scientists Will Use Insects for Control
Date: July 11, 1997
Editor: D'Lyn Ford (505) 646-6528, dlford@nmsu.edu
LAS CRUCES -- Leafy spurge, a noxious weed common on millions of acres in states north of New Mexico's border, is spreading rapidly in the state, said a New Mexico State University range scientist.
"Leafy spurge is an aggressive invader that can squeeze out native plants on New Mexico's rangelands," said Kirk McDaniel, with NMSU's Agricultural Experiment Station (AES). "Outside New Mexico, annual economic losses due to reduced forage for livestock and wildlife range from $2.6 million in Wyoming to $76.3 million in North Dakota."
Recreational and ecological losses may be even greater.
As early as the 1910s, leafy spurge was recognized as a potential weed problem in North America, particularly in cool, moist areas. It was first discovered in New Mexico along streamsides and in high elevation pastures in the late 1980s.
The weed can severely irritate the mouths and digestive tracts of cattle, sometimes causing death. The plant's seed pods explode when dry, often projecting seeds as far as 15 feet. These seeds can live in the soil for up to 8 years before germinating.
In New Mexico, leafy spurge currently is scattered in small, isolated pockets that collectively comprise less than 200 acres, said Richard Lee, weed specialist with NMSU's Cooperative Extension Service. Most patches are located in mountain pastures and riparian areas, and are less than 5 acres in size.
However, Lee is concerned that leafy spurge is widely distributed in parts of the San Juan, Sangre de Cristo and Sacramento mountain ranges. "The current distribution suggests leafy spurge is likely to spread into higher elevational areas throughout the state," he said.
Leafy spurge can spread quickly. For example, in North Dakota, an estimated 20,000 acres were affected in 1962, 40,000 acres in 1973, 86,500 acres in 1982, and nearly 1.2 million acres in 1990.
"Noxious weed management on public and private lands is complicated in New Mexico, because the state lacks weed laws to mandate control of invasive plants such as leafy spurge," said David Thompson, an entomologist with AES. "More than 80 percent of the known leafy spurge populations in New Mexico are on private land, and most are near riparian areas." Both of these factors make mandated weed control difficult.
Help may be on the way, however. McDaniel, Lee and Thompson recently received a grant from the Western Regional Integrated Pest Management Program to study controlling leafy spurge with Aphthona flea beetles.
In a previous study, Thompson found that these beetles feed on leafy spurge, removing more than 90 percent of plant mass within a 30-square-yard area around their release sites. Aphthona flea beetles already have been introduced into areas with leafy spurge in Montana, Wyoming and the Dakotas.
Thompson believes Aphthona flea beetles are the perfect choice for mass release. Adults move away slowly from their release sites, and the larvae responsible for most of the plant damage remain near their hatching sites.
To control isolated patches of leafy spurge in New Mexico, flea beetles will be collected from established insectaries in North Dakota and redistributed in New Mexico during a 3-year period. Once leafy spurge patches are severely damaged, spot treatment with herbicides or some other management technique will be used to eliminate remaining plants, Thompson said.