Illinois Natural History Survey - University of Illinois

On-site Rearing of Galerucella spp.

This program has been set up so that interested parties can rear beetles during the spring and summer without worrying about maintaining a colony of beetles all year round. Participants have enjoyed the process and produced extra beetles for release at their own sites.

Materials needed.

  • one small plastic wading pool 6 ft in diameter
  • 12 large pots (10-11 inch diameter will fit into the above pool)
  • potting soil
  • time release fertilizer
  • four ring tomato cages
  • fine mesh cages
  • duct tape and twist-ties
  • sunny location in which to place the pool and its contents
  • location to dig purple loosestrife roots

Dig Loosestrife Roots

This should be done in spring after the first shoots can be seen. Plants showing more than 10 dried stems from last year may be too difficult to dig and the root mass too large for a pot. Roots of plants with 3 -4 sprouts are usually ideal size. You will need to dig enough roots so that each pot has one large root or multiple small roots so that a minimum of 5 stems are produced.

Plant Roots in Pots

Mix time release fertilizer in with the potting soil. Half fill pot with potting soil, place root/s into pot and cover with potting soil to within an inch of the top of the pot. Make sure that each stem of the sprouted root is showing above the soil. Water at this time, make sure that the potting soil is saturated.

Setup In Pool

Add a tomato cage to each pot, pull a fine mesh bag over each cage and duct tape it to the pot. Close the fine mesh bag at the top using a twist-em. Place the covered pots into the pool and add water to the pool to a depth of 4 - 5 inches.

Watch Loosestrife Grow

The pool and contents must be placed where they will receive full sun for most of the day. Make sure there is always plenty of water in the pool as purple loosestrife does best when its "feet are wet"! Under these conditions the loosestrife will grow rapidly and within a few weeks the stems will be 2 - 3 feet tall. At this time they are ready for the beetles.

Watching the Beetles Do Their Thing

The number of beetles placed on each plant can vary. We normally place 20 on each plant and that seems to be enough. Too few and the plant will not be fully utilized, too many and there will not be enough plant there to take care of all the eggs/larvae produced by the adults. Once on the plant the adult beetles will feed, mate and begin to lay eggs. After about two weeks the adults will be difficult to find but you will gradually begin to see the larvae on the leaves and the appearance of the plant will change drastically. Depending on the temperature all the eggs will be layed and larvae develope in a 6 - 8 week period.

Harvesting The Next Generation

After a 6 - 8 week period you will see beetles around the top of the mesh bag. This is the beginning of the next generation. Now is the time to open the top of the mesh bag and collect the beetles with an aspirator. After this is done lower the mesh cage to the bottom of the pot and cut the old plant off at the ground level. Then pull the mesh bag back up over the tomato cage and close. As the beetles continue to emerge over the next two weeks they can be easily collected from the mesh cage using an aspirator. Emerging beetles are looking for food as soon as they emerge so if you cannot collect them each day, place a bouquet of loosestrife foliage inside the mesh bag for them to feed on.

Information on this page maintained by David Voegtlin.



Illinois Natural History Survey

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