To Protect their Bees, Alfalfa Seed Growers Embrace IPM
A lot of growers take steps to protect beneficial insects as part of their integrated pest management programs, but how many have speed limits?
Alfalfa seed growers in Washington’s Walla Walla Valley do.
The insect-driven speed limit – believed to be the only one in the nation – is designed to protect the area’s native ground-dwelling alkali bees. They pollinate alfalfa seed, and the 8 a.m. to 8 p.m. speed limit is only one of many measures area growers take to protect and promote the bees.
“All we do here is raise alfalfa seed, and we take great pains to protect those bees,” explained third-generation alfalfa seed grower Mike Ingham. “We have a very intensive integrated pest management program and one of the reasons is to protect these native bees.”
Every day during the summer blooming season, you can see at least one of the dozen or so area growers riding a motorcycle out into their fields with a sweep net to check for beneficial insects and pests – primarily Lygus bugs. They avoid harsh insecticides once the bees begin emerging from their underground nests. They only spray at night when the bees aren’t flying. They pay a voluntary assessment to support Washington State University research on bee-safe insecticides and other ways to protect and promote their alkali bees. They build new bee beds and maintain old ones, creating ideal habitat for their unique ground-dwelling bees.
Growers invest in their bees because the bees benefit their bottom line. And so far it’s worked. Alkali bee populations have plummeted in other regions, but remain plentiful enough in southeastern Washington to be economically significant for growers. But it’s delicate.
The bees’ survival is due to several interconnected factors, many out of the growers’ control.
It would only take one domino to fall the wrong way – one new potato field to be sprayed with the wrong chemical for example – to threaten the native bee population and the area’s alfalfa seed industry.
“We can’t grow other crops here,” said Mark Wagoner of Wagoner Touchet Farms. “Alfalfa seed is what we do.”
It Starts with Water
The growers in the Walla Walla Valley have access to irrigation water from the Walla Walla River until the first of June, then after that any water they use has to be pumped from underground. That’s expensive and essentially limits growers’ options to dryland crops.
And because the alkali bees are there, growers have taken advantage of them by growing alfalfa seed since the 1950s, rotating every four years or so with wheat. In those early days, the alkali bee populations were high enough to pollinate all the fields on their own and growers didn’t have to import Canadian leafcutter bees to supplement their pollination force.
“Alkali bees are natural pollinators, very effective and didn’t cost us any money,” remembered Russ Byerley of 5B Farms.
That changed in the late 1990s when a combination of bad weather and a pesticide application on a potato field knocked back the alkali bee population so bad that growers had to begin using leafcutter bees to pollinate their fields. Like the alkali bees, the leafcutter bees physically gather pollen from the alfalfa flower, and in doing so release some pollen that pollinates the plant and begins formation of seeds. (Honeybees, in contrast, gather nectar from the flowers and are ineffective pollinators of alfalfa.)
Now, growers can spend about $300,000 a year buying leafcutter bees, and another $50,000 building and maintaining bee beds for the alkali bees. To build a new bee bed, they’ll install subsurface irrigation to keep the ground moist, then apply tons of salt on top to mimic the alkali beds the bees prefer.
“This is a unique farming system where growers spend more on insects than they do on chemicals,” explained Doug Walsh, the Washington State University entomologist who works extensively with the industry. And not just a little more.
“My chemical costs are about half of my bee costs,” Byerley said. “Our bee costs are by far the biggest expense we have on the farm.”
To protect their insect investment, all the area growers are high-level IPM practitioners and ardent bug counters.
“The most important piece of equipment we have is a sweep net,” Ingham said. “You make one 180-degree sweep and start counting.”
The growers can all identify the beneficial insects in their fields as well as the pest insects – typically aphids in the early season and Lygus later. They use pest-beneficial ratios and thresholds to determine when to spray – even if they’re not quite as scientific as a published guideline might suggest – and they carefully choose and rotate insecticides when necessary to control their pests while preserving their bees and beneficials.
“You don’t want to spray until you have to because there is always risk to the bees,” Ingham said. “It’s always a balance between controlling our harmful insects and not killing our predators and pollinators.”
Walsh helps growers with that by conducting insecticide trials of different products to determine which can be used in the alfalfa seed fields with less risk to bees. Those tests used to just look at mortality, but have become much more complex.
“Now we look at sub-lethal effects as well,” Walsh said. “Does their behavior change? Can they find their way back to their nests or do they wander around aimlessly? It’s a lot of time looking at video of bees.”
Walsh’s work helped get the insecticide Flonicamid labeled for use in alfalfa seed, which is very effective at controlling piercing insects like aphids and Lygus bugs, while being very benign to bees and predatory beneficials like big eyed bugs, assassin bugs and spiders.
He’s also done projects looking at ways to build better bee beds for the alkali bees.
“Research is a key part of our success,” Wagoner said. “Alfalfa acreage is declining nationally, so there is pressure on seed producers. The research coming out of WSU keeps us competitive.”
The alfalfa seed industry recently published a new pest management strategic plan highlighting not only the ongoing pest management challenges growers face, but documenting all they do to protect the pollinating insects that are vital to their crops.
Since the alkali bee populations crashed nearly 20 years ago, all the Walla Walla Valley growers buy leafcutter bees. But at least some are beginning to wonder if they could change that practice.
Both types of bees have similar lifecycles. The females gather pollen and take it to their nests – underground for the alkali bees or in holes drilled in “bee boards” for the leafcutters. They’ll create several pollen balls, they lay an egg on each on before the adult bee dies. The hatched larvae feed on the pollen, overwinter in their nests, then emerge in the spring.
“I’ve been buying the same number of leafcutter bees for the past 10 years, but the alkali bees are coming back,” Byerley said. “Could I reduce the number of leafcutter bees? They go for the same food source, so maybe the number of leafcutter bees we import is limiting the alkali bee population.”
But because growers never know how many alkali bees will emerge, cutting back on leafcutter bees would be a huge gamble.
“I can adjust the number of leafcutter bees I buy,” Byerley said. “I can’t adjust the number of alkali bees in the ground. That’s impossible to measure.”
Another balancing act growers face is having enough bees to pollinate their fields, but not having too many competing for the limited supply of pollen. After years when he’s had full pollination and a really good crop, Byerley says he doesn’t get the same number of juvenile bees emerging the next year because there wasn’t enough stored food for the larvae. In years when his fields aren’t quite fully pollinated, he sees good emergence numbers.
“But if you have a good crop, you can afford to buy bees,” he said. “There has been talk of figuring out something we could plant that blooms later than alfalfa that could be an additional food source for the bees. That might help, too.”
Because the growers know, if you take care of the bees, they’ll take care of you.