For western alfalfa growers, two new pests already appear to be troublesome and difficult to control.
alfalfa leaf tear (Dicomeris acuminatus) and the angle of the dotted line (Psamatodes abydata) were discovered in lowland desert alfalfa in 2021 and 2022, respectively, according to Michael Lesswish, an entomologist at the University of California Cooperative Extension in Bryce.
Since then, the insect has been a previously unreported caterpillar pest in Alfalfa, both in the United States, and has become a particular problem in Imperial County, California, and Yuma and La Paz counties, Arizona. The county shares the Colorado River as a common boundary. Other alfalfa-growing regions in California, including the central valleys of Lassen, Modoc, Siskiyou, and Shasta counties and the mountains of northern California, are currently unknown for these insects.
Leaf tears have been widely reported throughout Arizona, including much of western and central Arizona, according to John Palumbo, an entomologist at the University of Arizona. Palumbo was unaware of reports in the southeastern corner of Arizona, which also has alfalfa acreage.
Alfalfa Leaftier starts out as green to off-green caterpillars and tends to reach about 9 mm in length. As caterpillars, they are characterized by black, hardened first thoracic segments and legs, which can be picked up with a sweep net, Rethwisch says.
Adults are about the same size as the bollworm, he said. It is characterized by a black spot on each forewing and a dark oblique line at the tip of the forewing.
This insect got its name from the way it binds alfalfa leaves. This makes it difficult to spot the small caterpillars as they use the tied leaves to hide and feed on the leaves. The ensuing eating disorder can look like a fallworm and can be serious, he said.
From Florida to California
Seasonal sightings of leaf tiers in Arizona have been reported from September through November. In California, these reports he continues from September through January. Elsewhere in the United States, insects have been reported in Florida and Mississippi.In Florida they have been reported year-round.
Rethwisch reports that the Reef Formation has other hosts reported in the southwest, including Sesbania, Paloverde and Mesquite.
“It’s possible that this is a year-round pest,” Rethwisch said.
Dot lined angles also appeared in low desert alfalfa. This insect is three times as long as he in the alfalfa leaftea. This pest was first reported to him by Rethwisch’s Pest Control Advisor last October.
This insect undergoes a more dramatic transformation as a caterpillar, says Rethwisch. It changes color and shape as it ages and transitions into a moth. Photographs from Mississippi State University suggest that the same moth can have different wing shapes and variations depending on its location in the United States. Dotted angles have been reported in most Southern states, except New Mexico, and Midwestern and Northeastern states.
Since the bug is new to California and the Southwest, Extension experts continue to research pesticides and biological control methods, Rethwisch said. Alfalfa growers in Arizona and California or who believe they may have discovered new caterpillars in their fields, he advised the PCA to contact local extension entomologists to confirm their identification. It is recommended. UC Joint Extension. The UCANR blog on Alfalfa Leaftier is at found here.
