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New Mexico State University

New Mexico State University

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Bagworms Becoming More Common in Northern New Mexico

LAS CRUCES -- Bagworms are becoming a major problem in parts of central New Mexico. The insects are moving in from eastern areas of the United States and New Mexico on infected nursery stock, said a New Mexico State University forest entomologist.


"They've been common in communities in the eastern plains for quite a while now, but they've just recently become a big problem in Albuquerque," said Bob Cain with NMSU's Cooperative Extension Service. "In the last few years, defoliation has been more and more noticeable."

"Bagworms are actually moths that spend their entire larval stage within individual silken bags," Cain said. Newly hatched larvae spin bags around their bodies as soon as they begin to feed and continue to enlarge the camouflaged bags as they grow. An opening at the top of the bag allows the insect to feed.

Bagworms attack a wide variety of trees, he said. In eastern states, they prefer arborvitae and red cedar, but also feed on pine, spruce, black locust, sycamore, willow, maple, elm, basswood, poplar, oak and cypress. Damage in Albuquerque has been most noticeable on locust, sycamore, crab apple, cypress, spruce and arborvitae, especially in the Old Town area, Cain said.

Conifers, or cone-bearing trees, usually sustain more damage because needles are not replaced as quickly as the leaves on deciduous trees, which fall off at the end of each growing season.

Now is a good time to inspect plants where bagworms fed last summer, Cain said. "If you have bagworms on your trees, one of the simple things you can do right now is remove the bags because the eggs are inside. You'll greatly reduce the population on individual trees by handpicking the bags and destroying them."

Cain said bagworms shouldn't be confused with fall webworms, which are common on deciduous trees throughout New Mexico. "Fall webworms are the ones that make the big silk tents throughout the canopy of large trees," Cain said. Fall webworms are not as damaging to the tree as bagworms, he said. Bagworms make a bag around each individual caterpillar, while the fall webworms make a silk tent or bag in the crown of the tree.

For more information on insect control, contact Cain at (505) 827-5833 or your local county Extension office.