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Pests

With growing challenges frequently coming in the form of fertility, moisture and weeds for forage producers in northwest Wyoming, alfalfa weevil and cutworms can also present a problem, as the endemic bugs can severely decrease yields in alfalfa fields.

“Weevil is a rough bug to deal with,” comments Jeremiah Vardiman, University of Wyoming (UW) Extension specialist in Park County. “We’ve had it here in Wyoming since the 1950s, so it’s nothing new.”

Changes

However, Vardiman notes the presence of weevil has changed in fields over time. 

“Recently, producers have told us there’s been a change in the timing as to when they see weevils,” he explains. “In recent years, the weevil has appeared in first-year stands, where producers might not have seen large populations until the third or fourth year of a stand in the past.”

“In the past, they only sprayed weevils once the year they found it, but now they have to spray once – if not twice – every year,” Vardiman continues. “We’re no longer breaking the pest cycle, which is a concern.” 

Looking at weevil

Alfalfa weevil is a snouted beetle that is slightly bigger than a grain of rice. During the summer months, it can be found in alfalfa fields, and it spends winters in the crown of the alfalfa or in the grass at the edges of fields. 

“Now, we also see weevils moving up the dry canyons in Utah, for example,” Vardiman says. “They come back to the fields in the spring and lay their eggs.”

Each female lays between 500 and 800 eggs in the stalk of the alfalfa plant. 

“The eggs hatch and release larvae that are grub-like,” Vardiman explains. “The grubs cause the damage to the plant.” 

The larvae move to the tips of alfalfa, eating the tips of the leaves during the third and fourth instar stages. By the fourth instar stage, they are visible to the naked eye and cause the majority of damage to the plan. 

“Recent studies say we are now seeing multiple hatches per year, but we don’t know why,” he says. “We see two and even up to four hatches of weevils each year.” 

Taking action

For producers, addressing alfalfa weevil means diligent monitoring and spraying of insecticide for control.

“We can only control the weevils that get hit by insecticide,” Vardiman says. “If they’re inside the whorl of the leaves, they’re protected and can survive.” 

Additionally, insecticides have no impact on adult weevils. 

“With multiple hatches coming, it is hard to spray just once and see weevil control,” he comments. “If we’re selling hay, it’s hard to be out multiple times in a sprayer and make it worth our money, so producers should be careful with their management.” 

Working with Extension, producers may be able to determine the optimal time to spray using a growing degree day calculator. 

Anecdotal information

“We have seen anecdotal information recently about a gentleman in Fremont County who raises alfalfa but doesn’t see any problems with weevils,” Vardiman comments. “He grazes his pastures with horses in the winter and early spring.” 

Vardiman says it is possible that the large number of horses from a pack string depletes the weevil population through crushing and habitat removal. 

He adds, however, “I’m not encouraging everyone to graze all their alfalfa fields with large numbers of horses though.”

Cutworms

While alfalfa weevil is a challenge for many producers, the emergence of cutworms resulted in partial control of weevil. 

“A producer in Laramie County sprayed the border of their field for the purpose of controlling weeds and Army cutworms,” Vardiman says. “They found the strip that was sprayed had really good control of cutworms and weevil both.” 

He continues, “However, the middle of the field was riddled with weevils.”

“We need to talk about weevil control and how we can achieve control into the future,” Vardiman adds.

Vardiman was one of a series of speakers who looked at forage production issues at 2019’s WESTI Ag Days, held in mid-February in Worland. 

Saige Albert is managing editor of the Wyoming Livestock Roundup. Send comments on this article to This email address is being protected from spambots. You need JavaScript enabled to view it.

“This first-of-its-kind project gives our national forest additional tools to get ahead of the pine beetle on a larger scale and could serve as a blueprint for other western states to follow.” – U.S. Representative Kristi Noem (S.D.), discussing the Black Hills National Forest’s Mountain Pine Beetle Response Project that will thin 248,000 acres of the forest in northeastern Wyoming and western South Dakota to get ahead of the mountain pine beetle.

 

Although the trend toward heavy grasshopper infestations continued this year, local Weed and Pest supervisors from around Wyoming say their program focus tended to shift away from rangeland toward alfalfa, crop and pasture lands.

“It seemed like our focus was more on crops grasshoppers this year – that’s where we spent most of our money,” says Washakie County Weed and Pest Supervisor Jarrod Glanz of their 2011 emphasis. “Where we had grasshoppers in rangeland last year there were very few this year – it was the opposite of what I was expecting.”

Washakie County treated 56,000 acres in 2010, while in 2011 they only treated 26,000 acres.

“Most of the grasshoppers we saw hatch this year were right next to the croplands,” notes Glanz.

In Spring 2011, Weed and Pest districts throughout the state continued with early landowner enrollment in cost-share grasshopper control programs.

“We help, we don’t take the lead,” says Big Horn County Weed and Pest Supervisor Ruth Richards of working with landowners. “Our policy was 50 percent cost-share on insecticide, and a dollar per acre cost-share for labor.”

Richards notes that landowners need to have their own grasshopper management plan, and Weed and Pest is very responsive to requests for help developing one with all the options.

Richards says that in 2011 Big Horn County’s grasshopper populations were similar, if not slightly higher, than they were in 2010.

“Our population areas were the same, we just heard from landowners we hadn’t heard from before who had suffered for a year or two and never contacted us,” says Richards. “If they don’t come to us early, in March or April, then we don’t know there’s a problem, and when they come to us in July and August it’s beyond our abilities to help them, because early treatments are affordable and effective, and late season treatments are expensive and less effective.”

“It’s a timing issue,” says Glanz of grasshopper treatments. “When most people around here see grasshoppers they’re up and flying, which means they’re way too big for Dimilin, which is the least expensive treatment.”

Big Horn County treated just under 50,000 acres by plane in Summer 2011, and the landowner-driven spray blocks stretched from the north end of the county to the south. However, Richards says the grasshopper program wasn’t only limited to larger-scale pastures and hay fields – it also included smaller areas of lawn, garden and ornamental situations.

To educate county landowners about the available assistance, the district held one large workshop and 10 community meetings.

“This year we had more funding and catered to smaller acreages, whereas before we didn’t have products for ornamental or residential use,” says Richards.

In Fremont County, Weed and Pest Supervisor Lars Baker says he thinks grasshopper populations were a little lower in 2011, but that the district sprayed many more acres.

“We sprayed a lot of alfalfa, so we didn’t have as much crop loss this year, because we were a little more aware of how much damage the grasshoppers can actually do,” notes Baker.

Baker calls the Fremont County cost-share program “healthy,” adding that the district spent about $200,000 to protect cropland acres.

“We were able to mitigate a lot of economic damage,” he adds.

Big Horn County spent $100,000 in county funds, which were aided by financial support from the Emergency Insect Management Grant from the Wyoming Department of Agriculture. Glanz says that Washakie County’s control program also benefitted from state help.

“We had more landowners participate, but we also had more funding through the state grant, so the cost-share was basically the same,” he says.

In Goshen County, Weed and Pest Supervisor Steve Brill says that although 126,000 acres were protected last spring, only 38,000 were actually treated.

“Many of the areas that were treated in 2010 didn’t need to be treated this year,” says Brill, adding that he’s not yet sure of a 2012 program. To date the district has been able to cost-share through the state grant, providing 50 percent on household treatments, 100 percent on state lands and 50 percent on the pesticide to treat the perimeter on croplands. However, Brill isn’t sure if state funding will be available in 2012.

“We also had great financial and technical support from the Worland Field Office of the BLM,” says Richards of working on federal lands in the Big Horn Basin. “They were great with providing us funding so the plane could continue from the field borders to the rangeland.”

Although many producers who graze livestock on the Bighorn Mountains say that they saw an increase in grasshopper populations at higher elevations on their grazing permits, the Forest Service does not have any strategies to deal with the insects. However, Forest Service Rangeland Management Specialist Scott Gall, who works in the Buffalo Field Office, says he anticipates the federal land management agency would be open to a control program, as it does already work with county Weed and Pest districts on noxious weed control.

“We hope to have more participation next year,” says Richards of her county’s control program. “I think we’ll have a similar grasshopper problem, and more people are becoming aware of the Weed and Pest programs. Anytime January through April is a great time to plan for grasshopper management.”
Glanz says he hopes the grasshopper infestation begins to decline soon.

“Many supervisors can attest to the fact that our whole summers are consumed by grasshopper treatment,” he says.

Christy Martinez is managing editor of the Wyoming Livestock Roundup and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

When conservation measures are implemented across the landscape, Thelma Heidel-Baker, a conservation biocontrol specialist with the Xerces Society, an invertebrate conservation organization, notes beneficial insects can provide natural pest control in agriculture systems. 

“Numerous measures can be taken to support insects and insect communities that also promote good soil health,” says Heidel-Baker.

Importance

Often, when people focus on pest management, Heidel-Baker says landowners tend to focus on insects as a whole, neglecting the fact that only two percent of insects are actual pests. 

“The rest of insects are for decomposing, making new soils and other things,” she explains. “Even though it’s easy to focus on the pests, other insects are vitally important.” 

One study referenced by Heidel-Baker showed that beneficial insects may generate between $4.5 and $12 billion annually for U.S. crop production, a figure that increases to $100 billion when crops around the world are considered. 

“This is a conservative estimate,” she says.

Beneficial insects are often present, but they aren’t easily seen or noticed, Heidel-Baker adds. 

She explains, “Many of our beneficial insects are tiny. A parasitoid wasp is only one to two millimeters long. They can be extremely critical.”

“Just because the insects are tiny doesn’t mean they aren’t really important or that they don’t provide critical natural pest control,” she adds.

Habitat

When looking at utilizing insects for pest management, Heidel-Baker says, “Habitat is the key component, as we have to make sure we’re providing the best environment for promoting insects.” 

“Pests thrive in monoculture systems because those systems provide the plants the pest needs,” she explains. “Beneficial insects need a more diverse habitat because they are a very diverse community.”

Landscape complexity helps to enhance beneficial communities for insects, but there were also other challenges. 

“Creating good habitat is not the only important piece,” she comments, “but there are a lot of other challenges that occur.”

Landscape challenges

Across the landscape, Heidel-Baker says the loss over 9 million acres of grassland and prairie have been converted to cropland because of the high value of crops, which is a detriment to insects. 

“Another challenge is in the broad use of pesticides,” she comments. “Insecticides are used extensively across large expanses of acres.” 

In particular, neonicotinoids are a concern because they are long-lasting, highly mobile compounds that are utilized worldwide. 

Not only do the insecticides kill beneficial insects, they also kill the food for remaining beneficial insects. 

“Because our beneficial insects are also predatory, if we kill all the pest insects, we need to provide an alternative prey source for those beneficial insects when we use insecticides,” Heidel-Baker notes. 

Habitat for insects extends beyond floral resources and extends to the broader community of plants in a landscape. It also includes providing pollen and nectar to beneficial insects, as well as their prey.

Additionally, it is important to have shelter for egg-laying, reproduction and overwintering, as well as protection from predators and pesticides. 

Diversity

Beneficial insects are diverse in their nature, and native lady beetles are a well-known group. 

“They’re great at feeding on soft-bodied insect pests like aphids, mealy bugs and more,” Heidel-Baker says. “In the larval stage, they are also predatory.”

Lacewings are another important in different stages of their life. The adults aren’t predatory, but their larvae are aggressive predators that move around to hunt and search for their prey.

Parasitoid wasps impact predators by laying their eggs in larvae, where they develop into amture wasps. Additionally, Heidel-Baker noted they require specific habitat because they don’t have any other prey than aphids. 

Hover flies and the assassin bugs work in different ways to attack insect pests. 

“Another important group as we think about soil health are predatory grounds beetles, which live at the interface of plant and soil,” Heidel-Baker says. “They are down at the soil surface, which are important for controlling predators like grubs, and they can be important for weed control.”

Farm practices

Because of the importance of beneficial insects, several farming practices can be implemented to promote insect growth.  

She says, “Healthy crops ensure good things happen in our habitats. When crops are healthy, they create a resilience against insect pests that might occur in the first place.”

By deterring insect pests, the use of insecticides is alleviated, allowing plants to address pest issues on their own. 

Healthy soils are the foundation of ensuring healthy crops, adds Heidel-Baker. 

“One of the really important practices that has come to light recently to promote beneficial insects and soil health is the use of cover crops,” she says. “More farmers are looking at cover crops because they provide a ton of benefits across the farm.”

In addition to helping improve soils, cover crops can support insects and pollinators. 

Heidel-Baker comments, “We know ag practices impact diversity and abundance.”

Heidel-Baker spoke during a National Association of Conservation Districts (NACD) soil health webinar in mid-November 2017. The webinar was hosted by the NACD Soil Health Champions Network.

Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

Riverton – Although they may be small, rodents can adversely affect irrigation, electrical supply, crop production and tree survivability.

“They can really start causing damage in a variety of different places,” commented University of Wyoming Pesticide Coordinator Jeff Edwards.

Voles, kangaroo rats and prairie gophers are three examples of potentially harmful rodents discussed by Edwards at Fremont County Farm and Ranch Days on Feb. 11 in Riverton.

Voles

“Voles look a lot like mice, and people confuse them, but voles are stocky and have relatively short tails compared to their body,” he noted.

Their body shape somewhat resembles a guinea pig, with small ears and a grizzled-fur appearance. They range from about 4.25 to seven inches long with relatively short tails, compared to their bodies.

“There are a bunch of different species in Wyoming, including water, pine, meadow, sagebrush and prairie voles,” he explained.

Females can produce multiple litters per year, and species populations can fluctuate wildly.

“We can go for years without having voles or seeing voles, and then all of the sudden they are there,” he added.

Causing damage

Insects and plants make up the majority of their diet, and voles will eat grasses, sedges, alfalfa, grains and berries.

“They have the ability to go down planted rows and harvest the seeds that we have just planted,” he commented.

Voles have also been known to eat the bark, girdling the trees that they eat.

“If we happen to have fruit trees in our yard, we might want to check the bases of those trees for gnaw marks,” explained Edwards.

Vole activity can often be identified by shallow burrows extending to a series of surface tunnels that they use to stay hidden while foraging for food. Grasses near the tunnels are usually clipped short, close to the ground.

“Considered to be secretive and seldom seen, we do end up seeing the runways as a result of their activity in and around these systems,” he said.

Voles are active both day and night, unlike nocturnal kangaroo rats.

Kangaroo rats

“Kangaroo rats have small forelegs and long, powerful hind legs with a long-tufted tail,” described Edwards.

Body length varies from four to six inches, with tails ranging from six to eight inches long. They typically have wheat-colored fur on their topside and white fur on their belly.

“Also, they hop. That is why they are called kangaroo rats,” he explained.

Impacts

Kangaroo rats can also take planted seeds out of farmers’ fields, and they can consume large amounts of material.

“A medium population density can consume 1,300 pounds of plant material per section, as well as store 2.9 tons per section per year in burrows,” added Edwards.

That could be enough to replace six cow/calf pairs on a section.

“They are considered hoarders, and in their intricate tunneling systems, they have pockets where they bring seed back and store it for wintertime,” he stated.

Pocket gophers

Pocket gophers are also hoarders. While they are out collecting food, they pack their cheeks with extra supplies to store for later.

“The most characteristic feature of pocket gophers is their large external cheek pouches, which are actually outside of their mouths. The pockets are fur-lined, and the gophers can turn them inside-out to empty them,” explained Edwards.

Generally six to eight inches long, they have relatively short tails in relation to their body size and large front claws used for digging.

“Moles and gophers can be confused because they are quite similar in appearance. Moles have highly reduced eyes and pointier noses,” he commented.

Dietary preferences

Pocket gophers primarily eat roots, but they also occasionally eat worms or insects.

“They really like alfalfa and the roots of small immature trees,” he said.

Along with new plantings of trees, electrical wires and irrigation lines can also be susceptible to gopher damage.

“They are very territorial. If we happen to come across one of their tunnels with an electrical line or something that we are putting in, they see that as a threat, and they will start gnawing through it,” he commented.

A minimum of two-inch PVC schedule 40 pipe is recommended to protect underground lines in pocket gopher territory, as they can chew up to 2.9 inches in diameter.

Control

“We can trap gophers,” stated Edwards.

He warned that trapping is more effective when producers understand how rodent tunneling systems work.

“If we come across a gopher tunnel, there are two directions we can go with a trap. We generally need two traps with some sort of solid spike to hold that in place,” he explained.

Baiting and bait traps can be effective for pocket gophers, kangaroo rats or voles, as long as they are used correctly. There are a variety of snap-traps for prairie gophers, rat-sized snap-traps can be used for kangaroo rats, but they are not effective for controlling voles.

“Baiting is the most common way to take care of voles,” he stated.

Kangaroo rats can often be controlled with flooding, but Edwards noted, “Although entertaining, shooting is not effective.”

For any control method, users should understand their environment and the species they are working with.

“Be sure to read and follow the labels,” Edwards said.

Natasha Wheeler is editor of the Wyoming Livestock Roundup and can be contacted at This email address is being protected from spambots. You need JavaScript enabled to view it..