Wasps may be drafted as the next deadly weapon against lygus bug infestation.
Hector Carcamo of Agriculture Canada’s Lethbridge Research Centre is working to identify lygus bug predators so canola and alfalfa producers can reduce their input costs by letting nature take care of the pest.
“The new work involves assessing what natural enemies the lygus bug has in the southern Prairies,” Carcamo said.
“We’ve done enough work with the chemical control strategies.”
The best candidate so far is from the Peristenus species of wasp.
Read Also
Genetic resistance for anthracnose is on the way
anthracnose resistant lentil varieites are on the way according to Ana Vargas, University of Saskatchewan lentil and chickpea breeder. She also shared some management methods for the anthracnose in lentils.
Carcamo said it attacks only lygus bugs and other species of plant insects.
The wasp kills lygus bugs in their nymph stage by incapacitating them and laying an egg inside.
“So instead of having an adult lygus produced from that nymph, you will have a wasp.”
Before Carcamo can put this new strategy to the test, however, he must identify Peristenus wasps that are native to the southern Prairies.
He doesn’t want to introduce a new species without knowing how it will affect the prairie ecosystem.
“We like to make sure that what we introduce here is not going to have a negative environmental effect on the native fauna.”
Carcamo said Peristenus wasps are rare in Canada.
“What they have found out in Eastern Canada, if you take about 200 sweeps, you will find only one tiny wasp.
“We’re still quite a ways away from bringing in the wasp, but what we hope to do is to release it in certain habitats such as weedy areas where we know that lygus have their first generation. And also, alfalfa fields.”
Carcamo hopes the wasp will establish itself in those areas so scientists will not have to reintroduce it every year.
He said Peristenus wasp tests on lygus populations in the United States have had positive results.
“They have introduced it into alfalfa fields and they are finding the wasp can be quite efficient in destroying about 70 percent of lygus populations in alfalfa.”
Carcamo expects similar results in Canada in canola and alfalfa crops.
Insecticides continue to be the traditional form of lygus control.
More than one million acres of canola had to be sprayed in Alberta during the 1998 lygus outbreak.
Chlorpyrifos (Lorsban), Trichlorfon (Dylox), and Lambda cyhalothrin (Matador), are all registered lygus bug insecticides.
Carcamo said his work with wasps is designed to reduce insecticide use.
“That is the goal.”
Biological controls such as the use of wasps cannot eliminate the lygus bug, only suppress it.
However, Carcamo and his associates have found that a small lygus bug infestation benefits canola at the early flowering stage, stimulating the plant to grow extra branches.
They have also found that the early pod stage is the best time to apply insecticides.
The ultimate goal, however, is to reduce the number of lygus bugs naturally, and put the remainder to work for the producer.
“Even if we could kill half of them in the spring, then there wouldn’t be enough to cause problems in canola,” Carcamo said.
