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Raising
Galerucella Beetles It is expensive to purchase beetles for very large infestations of purple loosestrife. The beetles cost about 11cents each, and several thousand are needed for every tenth of an acre. This spring the Cambridge Water Department purchased 5600 beetles for the Little Fresh Pond wetland that covers about 0.2 acres. Fortunately, methods have been developed so that people can raise their own beetles. Once a beetle population is established on a site (using purchased beetles) adults can be collected and placed in "beetle nurseries" where they lay their eggs in controlled conditions, and the next generation can grow without the danger of predators and other problems. Creating beetle nurseries is an educational project in which students and other members of the community can participate. The Water Department hopes to eventually grow their own beetles to use on scattered loosestrife stands at Fresh Pond Reservation, and perhaps to use in the Upper Cambridge Watershed (Hobbs and Stony Brook Reservoirs.) To learn the procedure, the Friends group helped set up a pilot beetle nursery project. The procedure we used at the Reservation, was the one described in the MOCZM guidance document. In mid-April we dug about a dozen loosestrife roots from the wetland at the north end of Little Fresh Pond. We put them in plastic trash bags for transport back to the Water Department where they were stored. On Saturday, April 22 the Friends group offered a program during which volunteers washed the roots and planted them in 3-gallon pots.A tomato cage was placed in each pot, and a cylinder of netting (bridal veil material) was pulled over the cage. The netting was attached around the pot with an elastic band, and tied at the top. When the plants were about 18 inches tall, their tips were pinched back so that the plants would branch. They quickly grew into 3 foot tall, bushy plants. On the evening of May 31, the day the purchased beetles arrived, about 10-15 beetles were placed on each plant. The netting was secured so that no beetles could escape and no predators could enter. Within a few
hours characteristic "bullet holes" appeared in some of the
leaves, an indication that the beetles were eating. We are currently
observing the plants and awaiting the appearance of eggs and larvae.
When the next generation of beetles emerges from the soil in August,
we will place the pots in areas where there are loosestrife plants that
have not yet been populated by beetles. Elizabeth Wylde |