Hot Stuff, Summer/Fall 1999
- Hungry, hungry hornflies (Fall 1999)
- No trivial pursuit (Fall 1999)
- Insects indicating unhealthy forests (Fall 1999)
- High-tech Hoover (Fall 1999)
Hungry, hungry horn flies
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"Shoo fly, don't bother me" could be the theme for cattle infested with horn flies.
"Horn flies are blood-sucking parasites that spend most of their life cycle on the animal, taking blood meals," says Ron Byford, a veterinary entomologist with NMSU's Agricultural Experiment Station and Extension plant sciences department head.
For the past 10 years, Byford has been studying how best to control the destructive flies. "The U.S. Department of Agriculture has determined that the horn fly causes about $730 million in damage a year to the cattle industry," he says.
Most of those losses are indirect. Horn flies feed as many as 35 times a day on an animal, causing irritation and annoyance that results in less weight gain, reduced milk production and decreased feed efficiency. A normal infestation could range from 1,000 to 3,000 flies per animal.
Horn flies have been difficult to control. As soon as producers find an insecticide that works fairly well, the flies develop resistance to it.
Most recently, researchers have been studying the effectiveness of insecticides applied with ear tags.
Early in the fly season, ear tags that have insecticide blended into them are put on the cattle. The tags remain in place throughout the summer and into the fall-sometimes for as many as five or six months. "The tags release small amounts of chemical over a long time," Byford says.
Because the flies are subjected to the insecticide for most of their lives, they are able to genetically adapt, and the insecticide becomes less effective.
In a year's time, there are about 15 to 20 generations of horn flies. "The flies that survive the insecticide have the gene for resistance and they pass that to their offspring," Byford says.
In the laboratory, he has been studying mechanisms the flies use to overcome the pesticides. The mechanisms may include a combination of biochemical, physiological and behavioral adaptations.
"By looking at the mechanisms, we're able to come up with new ideas, new alternatives with which to attack the fly system," he says.
Byford has been looking for chemicals that can increase the toxicity level of the insecticide and block the development of resistance.
"We've been looking at mixtures and rotations of various classes of insecticides," he says. "We have our own colony of horn flies that we maintain year-round. When alternatives look effective in the laboratory, then we transfer them to the field for testing."
What has worked best is alternating use of different classes of insecticides on a yearly basis.
The approach to studying resistance in horn flies could also be useful in dealing with other pests. "Because the horn fly almost never leaves the animal, it is a good target species to work on," Byford says. "If any insect is going to develop resistance, the horn fly inevitably will."
No trivial pursuit
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Budding entomologists can find an extracurricular activity to their liking at NMSU.
In February, entomology students in the College of Agriculture, Consumer and Environmental Sciences proved they are the best in the Southwest by placing first in the Linnaean Games, an entomology-based question and answer competition.
The contest was held in Las Cruces during the Southwestern Branch meeting of the Entomological Society of America.
The team, coached by NMSU science specialist David Richman, qualified to compete at nationals in December 1999 in Atlanta, Ga. The competition will be part of the Entomological Society of America's national meeting.
"We really are proud of the team this year," says Richman, who has been coaching Linnaean teams for about 10 years.
To win the regional competition, NMSU's team had to beat teams from Texas A&M and Oklahoma State University. Team members needed to know that the pecan weevil recently was found in Otero County and that the cochineal insect was used to make the dye found in the red coats of British soldiers during the American Revolution.
Focusing specifically on trivia about the field of entomology, the Linnaean Games are based on the old college bowl competitions, Richman explains.
To help prepare for competition, team members read entomology trivia and text books and study past Linnaean Games questions. Richman holds practice sessions complete with buzzers borrowed from the 4-H program.
The students may concentrate on becoming experts in certain subject areas, such as taxonomy, morphology or history of entomology.
The winning team included graduate students Andrine Morrison and J. Chris Romero and undergraduates Lupe Carrasco and Ricardo Ramirez. Senior Becky Whiteaker was an alternate.
Morrison, whose father and sister are entomologists, is looking forward to the national competition. When she has spare time, she only allows herself to read about entomology. "We will have the chance to do our best in front of the people that we will probably be working for if we stay in entomology," she says.
Morrison says the backbone of NMSU's team is Romero, who has been competing for four years. Romero says team members always have studied hard for the competitions, but he's really hoping they'll place nationally this year.
Romero, whose graduate studies have focused on biological control and insect rearing, has been interested in entomology since he took part in a state FFA competition in high school.
Insects indicating unhealthy forests
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Armed with only maps and colored pencils, a forest entomologist tracks killers. Inside a high-wing plane above the forest canopy, he charts their paths of destruction.
The tracker is Bob Cain, with NMSU's Cooperative Extension Service. The killers are bark beetles and Western spruce budworms.
Each year, Cain conducts aerial surveys of 1.6 million acres of the state's forest land. "We're in the air for about two weeks every July when color changes from insect damage are most apparent," he says.
From the paper maps, data is transferred to a computerized mapping system and provided to forestry districts, landowners and the U.S. Forest Service. "This archive of insect populations may help foresters identify areas where tree removal or insect treatment would be beneficial," Cain says.
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Bark beetles have been at outbreak levels since 1990 on ponderosa pine in the Lincoln National Forest. "Smaller outbreaks have been observed in all of New Mexico's forested communities," he says.
Bark beetle larvae tunnel under bark and kill trees by feeding on the soft tissue. They also introduce a blue stain fungus that interrupts the flow of water and nutrients within the tree.
"As these insects move from tree to tree, they transmit the fungus," Cain says. "Eventually, the needles turn red and the trees die."
During the time lag between beetle infestation and tree mortality, the trees remain green. "This can be an issue for homeowners buying trees from a nursery or foresters marking trees for removal," he says. Trees may appear healthy when they're not.
Cain says that past grazing, logging and fire suppression have caused forest overcrowding, with denser stands of smaller-diameter trees. "Some forest ecologists estimate that a tree must be at east 30 inches in diameter to provide long-term ecological benefits to the forest and its wildlife," he says. "Many of our trees aren't reaching that size." Crowding stresses trees, making them more vulnerable to insect attacks.
In addition to crowded conditions, tree species at unusual elevations are increasing. "We're seeing Douglas fir and white fir growing in lower elevations where before ponderosa pine predominated," he says. These trees are attractive to the Western spruce budworm.
"These moth larvae feed on buds and needles, causing defoliation," Cain says. "The severity of budworm damage has increased in the past 50 years, particularly in mountain communities near Taos, Angel Fire, Mora and Chama." Outbreaks are lasting longer and occurring at lower elevations.
Insects and diseases are natural components of New Mexico's forest ecosystems. Tree loss caused by these elements creates open areas that provide habitat for wildlife. But chronic diseases and insect outbreaks may be indicators of unhealthy forests, Cain says.
"As a society, we are moving toward a more preservationist attitude, where we want to protect the current state of our forests, even though current conditions may not be ideal," he says.
There is no easy solution to the forest health problem. "The present conditions have developed over many decades," he says. "Likewise, any efforts to improve forest health will be long-term."
High-tech Hoover
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Pink bollworms and pecan nut casebearers in the Mesilla Valley don't want to mess with Dr. E's Insectavac.
Joe Ellington, an entomologist with NMSU's Agricultural Experiment Station, says his high-vacuum machine will collect insects more efficiently than hand nets so farmers can get a better estimate of pest populations in their cotton fields and pecan orchards.
Better estimates mean farmers can make wiser decisions about how and when to control pests.
"By taking absolute samples, we can do a better job of analyzing precisely how many insects are in a field," he says. "It's sort of like going to Vegas and knowing what the odds are for or against you. That's the game we're playing here."
Ellington's research focuses on biological control of pests. "Classical biological control really means going to foreign countries and collecting the parasites and predators that attack insects where they co-evolved," he says.
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Natural parasites are then released into the environment to try to control the invading pests.
"Only about 5 or 10 percent of the insects in the world are harmful enough to cause us damage," he says. "So most of them are good guys out there, and if we can preserve those and build on them, I think we can eventually take care of the troublemakers."
For example, Ellington plans to mass release trichogramma, an egg parasite, to try to control pecan nut casebearer, a tiny, night-flying moth. Casebearer larvae eat developing nuts, which then drop prematurely.
In the future, Ellington also may use trichogramma to control pink bollworm in cotton. "To mass release trichogramma, we have to rear grain moths and then their eggs act as a host for trichogramma. So it's a fairly involved process," he says.
A new, state-of-the-art insectary, funded by Stahmann Farms of Las Cruces, should be ready soon to help researchers raise the beneficial insects for mass release. "The new facility will have very good temperature and humidity control," Ellington says. "It'll be closed off so insects from outdoors, such as grain mites, can't infest the cultures."
This summer, Ellington will try to release enough trichogramma to determine how many are needed per acre to achieve a beneficial level of casebearer control.
That's where the Insectavac and an electronic insect counter come in. "We vacuum up the insects, and then count and classify them by computer," he explains.
Collected insects are spread on a computer scanner, which converts the images into electronic information about their size, shape and color. The information is then analyzed by an insect identification computer program, developed in conjunction with NMSU's electrical and computer engineering department.
Ellington has been working on the insect counting system for a number of years and hopes to get the "bugs" out soon, so farmers can put the technology to use in their fields.