Bio Control Phase II - Beetles!

If you've been over to Assabet River National Wildlife Refuge this week, you may have noticed a strange set up of kiddie pools, plants, and mesh-covered tomato cages. What the heck are we doing now?

You might remember that we're growing purple loosestrife plants in those kiddie pools as part of our bio control efforts to keep wild purple loosestrife in check. The addition of the cages and nets are part of Phase II of our project - raising the beetles!


Dani (back) and Matt collect beetles at the Concord impoundments

On Monday, Katrina, Dani, and Matt visited locations within the refuge complex where Galerucella sp. beetles were released in the past.  Ultimately, they collected beetles from loosestrife plants growing around the edge of the ponds at the Concord impoundments. There are a lot of beetles still living in the impoundments, which is great news because we haven't been able to release new beetles there in several years!  We want the beetles to be able to sustain their populations in the wild so that they will continue to feed on the loosestrife and so we eventually won't need to continue helping them along with our breeding programs.


Beetles congregating at the top of a purple loosestrife plant



Eventually, the beetles will eat enough of the loosestrife's leaves that the plant will die


We collect the beetles one of two ways. The first is with an insect aspirator:

Aspirators are a little strange looking, but they are essentially human-powered vacuums that are used to suck up small insects (though you should never use this type of aspirator to remove insects from the nests of mammals or birds - the mesh keeps insects from flying through the chamber and into your mouth, but not bacteria, viruses, or microscopic parasites). To use an aspirator like this one, place the open end of the straw with the yellow mesh in your mouth. Direct the tube close to your target and suck in sharply. The insect should be sucked through the tube and into the chamber. The length of the tube can make it difficult to suck up your targets as you need a reasonable amount of suction to draw them all of the way through the tube. If you can get close enough to your target, you may also remove the tubing and simply draw the insect through the other straw.  Once we had about 20 beetles in the chamber, we transferred them to a collection vessel, which brings us to our second method of collecting beetles.

Fortunately for us, collecting beetles doesn't require a lot of high-tech equipment - just a little bit of ingenuity and finesse. To make our collection vessels, all we did was cut the top off of plastic bottles, duct tape the edges so we wouldn't hurt ourselves, and then invert the tops. When we got to the collection site, we put some loosestrife stems in the bottles to help shade the beetles and give them something to munch on. The funnel created by the top makes it more difficult for them to escape as we tapped them in from the aspirator, and then we just used a rubber band to hold a piece of mesh fabric across the top of the bottle to keep the beetles in line.

While we used these bottles to transfer beetles from the aspirator collection chamber, we also collected directly into the bottles. To do this, all we had to do was gently shake the leaves that the beetles were on over the open bottle. Galerucella beetles naturally drop off of leaves as a defense against predators, so they dropped right in to our bottles.

Once we have all the beetles we need (about 10-15 per potted plant), we get back to our rearing facility right away. We don't want to keep the beetles in the bottles for too long, because otherwise they might overheat. It wasn't too warm on Monday, but if it was hot out we would have kept the bottles in a cooler with ice. Because we put all of our beetles into two collection vessels, we had to count out the necessary 10-15 beetles for each pot as we transferred them to our plants. This proved a little more difficult than we expected...

Matt and Katrina carefully attempt to transfer beetles to our plants

Not all of the beetles we collected congregated on the stems and leaves we gave them, so several flew away as soon as we cracked open the bottles. Fortunately, about half of our loosestrife plants weren't tall enough to add beetles to yet, so they didn't have nets over them. Most of the beetles that flew out of the bottles landed on the exposed loosestrife, and we were able to put them back into the nets.

After only a day in the nets, our beetles are foraging away and some have even already laid eggs! We hope that by next week the other half of our plants will be tall enough to add beetles, and we will venture out on a second collection mission. We should also see larvae next week, as the eggs will hatch after 7-10 days. Stay tuned!

Galerucella eggs