State group hosts educational session

Alfalfa pests topic during Brown Co. Customer Appreciation

TORRINGTON – There are different methods of dealing with insects that attack alfalfa in the field.
That was the consensus during an educational meeting Thursday, Feb. 27, hosted by the University of Wyoming Extension Service, the Wyoming Hay and Forage Association and Brown Company in Torrington during the implement dealership’s annual Customer Appreciation Day.
“Everybody is using a different philosophy on their farm, so we can bounce ideas off each other,” said Mick Miller, one of the speakers and an alfalfa and forage specialist for CROPLAN. “We have common seed varieties we’ve built on over the past 70 or 80 years with new insect tolerance, new technology, that just lets you be better stewards on your place.”
How producers manage their fields can go a long way toward maintaining healthy hay and forage crops, Miller said. A University of Wyoming study showed reducing the number of annual cuttings from four to three leads to increased vigor of the plant as well as increased yield, for example.
Overall yield on test fields where the number of annual cuttings was reduced increased by 17% the first year and 25% during the second year of the study, for example, Miller said.
“The more intensively you cut alfalfa, the more you cut the lifespan of the stand,” he said. “If you can go and take a cutting out of there, you inadvertently keep the stand in there a little longer, which is better economically.”
Another method to bolster the health and vitality of alfalfa is how producers prepare the ground, Miller said. It’s important, but seed-bed prep isn’t something the average producer necessarily considers when making management plans, he said.
“No one ever thinks about how important bed prep is with alfalfa,” Miller said. “You need to do it right the first time.
“Pack it, seed it, pack it,” he said. “If you can bring a basketball out and dribble it on that ground, you’re about right. You can never have that soil bed too firm.”
In Miller’s experience, a no-till drill is his preferred method for planting alfalfa, he said. A planting depth somewhere between 3/8-inch and 1/4-inch are about ideal. But drilling seed in isn’t the only option that works.
“An air-flow truck, for example, takes a lot more pre-planting and post-planting preparation,” Miller said. “But some of the best alfalfa stands I’ve seen were planted with an air-flow truck. With the new traits in seed and technology, it’s even more important we do soil prep right the first time.”

Limiting pest infestations
But getting the seed in the ground, germinated and growing is only the first part of the process. How producers manage the myriad insect pests that prey on their crop is at least equally important, said UW Extension Entomology Specialist Scott Schell.
And making sure pests – particularly a pernicious invader known as the blister beetle – aren’t present in the fields or, more importantly, finished bales sold to hay customers is vital, Schell said. He pointed to the tale of a horse boarding stable in Wisconsin where several horses died due to blister beetle contamination in hay, some of which was eventually traced back to producers in Wyoming.
“The beetles will gather en mass on blooming alfalfa,” Schell said. “If the beetles are killed and incorporated into the bales, livestock that consume the hay is at risk from poisoning.”
There are four primary varieties of blister beetle common to North America, he said. The three most common in the Wyobraska area are the black blister beetle, the gray blister beetle and the spotted blister beetle.
A chemical defense common to the blood-analog of the blister beetles is responsible for their toxic nature, Schell said. If, for example, beetles are present on alfalfa plants during harvest and are crushed by the machinery, the chemical contaminates the hay, which then sickens or kills livestock, with horses being the most susceptible to its effects.
Fortunately for Wyoming producers is the most abundant variety in the region is the black blister beetle, which is overall the least toxic, he said. The most toxic – the striped blister beetle – isn’t typically found in this area.

Different concerns
Blister beetle contamination of hay needs to be put in perspective, Schell said. While it is a concern, it needs to be balanced against other potential contaminants, from moldy hay to the possibility of poisonous weeds being present in a field and inadvertently baled with the alfalfa during harvest.
And, while a concern, blister beetles do have a beneficial side. The larval stage seeks out and kills grasshopper egg sacs, he said.
There are several management options available to minimize the risk of blister beetle contamination, Schell said. Since the beetles are attracted to the blooming plants, timing harvest activities around blooms can reduce infestations, for example.
“And weed control around the fields to prevent other, blooming weeds that attract the beetles” can reduce populations, he said. “There are other forages people are experimenting with that could also attract the beetles. The flower is what makes the insects swarm.
“And grasshopper control – it’s always cheaper to control pests in a non-crop area than in a crop,” Schell said. “Grasshoppers generally lay their eggs in areas around forbs that grasshoppers like to eat.”
Integrated pest management options range from traditional chemical pesticides to biological controls – other insects that prey on pests, for example – to tillage and planting options to attract the pests away from the cash crop and into so-called buffer zones, said Randa Jabbour, associate professor in the plant sciences department at UW. One project she’s working on uses growing degree days to track pest development – particularly the “consistently problematic’ alfalfa weevil.
“The alfalfa weevil in Wyoming mostly overwinters as adults,” Jabbour said. “In some warmer places they can overwinter as eggs – we haven’t seen that in Wyoming yet, but we’re keeping our eyes out with recent warmer winters.”

Cost vs. benefit
Pest management is always a balancing act, she said. With the cost of pesticides, producers need to decide if the expense of chemical applications is balanced out by any financial gains realized from doing away with yield reductions caused by predation.
“The decision threshold is based on the price for hay and the cost of insecticide,” Jabbour said. “What is a reasonable tradeoff between the cost and what you can get for your hay?
“We want to help people apply stuff as effectively as we can,” she said. “We’re also interested in people balancing removing pests while keeping beneficial insects.”
Another concern is the possibility of pest insects developing resistance to common insecticides. While there are indications resistance may be developing in alfalfa pests in other parts of the country – specifically California and Colorado – there isn’t confirmed resistance issues in Wyoming, Jabbour said.
“But, if you’re concerned about this and you think maybe we’re losing efficacy of pyrethroids, there’s a group – – that track that,” she said. “It’s something other folks are working on and you can get some good answers.”
There are other, non-chemical management practices Jabbour is studying that may be proving effective in combating weevils specifically, as well as other pests, she said. Leaving small areas of fields or buffer zones untreated will attract insects to those areas, reducing damage to larger swaths of the crop, for example.
“And we’re looking at optimizing early harvest,” she said. “But how early is too early? We don’t know how harvest time affects weevil mortality yet, that’s what we’re trying to find out.
“There are so many things we don’t know right now,” Jabbour said. “But I think making fields inhospitable for the weevils is important.”


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