Fresh Pond Reservation
Purple Loosestrife Biocontrol Project
Raising Beetles Experiment
January 9, 2008
In the spring of 2007, the Friends of Fresh Pond Reservation and the Cambridge Water Department, with assistance from the Maynard Ecology Center, began a pilot program to raise beetles of the genus Galerucella to release as part of the Fresh Pond Reservation Purple Loosestrife Biocontrol Project. The program was developed from protocols created by the Invasive Plant Coordinator at the Rachel Wilson Wildlife Refuge in Wells Maine, and by the Center of Urban Ecology and Sustainability at the University of Minnesota Extension Service.
Six nurseries were created by Friends of Fresh Pond Reservation volunteers, 4 others were planted and raised at the Maynard Ecology Center. To create the beetle nurseries, the roots of purple loosestrife were dug from the wetland on the northern end of Little Fresh Pond with the help of Fresh Pond Reservation Ranger Charles McNeeley. The root balls were cleaned and planted in individual pots with tomato cages. The pots were covered with netting that was secured at the bottom with rubber bands, and tied over the tomato cages. The netting was used to both keep predators out, and to keep the beetles in. The plants were transported to a secure location on the Reservation and placed in water-filled dish pans to simulate a wetland condition.
Some issues with the nurseries arose almost immediately. Once wet, the rubber bands would disintegrate, compromising the nursery and perhaps exposing the plants-and eventually the beetles-to predators. The rubber bands were replaced by twine on some of the plants later in the season, which seemed work better. The netting around the plants turned out to be too delicate, and ripped. Some of these holes were repaired with duct tape, which seemed to hold up well.
The loosestrife plants were watered on a biweekly and then daily basis. On May 31, 2007, 5,500 Galerucella beetles arrived from the NJ Department of Agriculture's Phillip Alampi Beneficial Insect Laboratory. Most of the beetles were released into the wetland north of Little Fresh Pond. Using aspirators and film canisters, Elizabeth Wylde and Hannah Wilbur collected about 100 beetles and placed them in a large container, along with a number of purple loosestrife stems equaling the number of nurseries. The hope was that the beetles would become evenly distributed on the stems, and then a stem could be placed in each nursery. In the evening, the stems were distributed to the nurseries during a beetle release party event.
The beetles were to mate, lay eggs, and then die off, leaving the next generation of offspring to grow on the nurseries. Evidence of initial herbivory was apparent on most of the plants, and beetle larvae were observed on many of the plants as well. Despite being watered on an almost daily basis, it was difficult to keep the dish pans from drying out.
The nurseries at the Maynard Ecology Center were transported to the Water Department at the end of the school year so that they might be cared for all together. Once the plants became very large, they became top heavy, and would fall over in the wind despite being in a sheltered area. This caused the netting to rip on several occasions. Also, due to the drought, some of the plants became desiccated, and were abandoned.
By August, when the beetle nurseries were put out into the linear wetland along Fresh Pond Parkway, only three of the initial 10 nurseries were viable. While the overall experiment had middling results, several important lessons were learned during this initial raising program.
The netting should be slightly thicker, so that it might withstand use through the entire season. After being exposed to both rain and sunlight, the material became quite brittle and was prone to ripping, allowing predators and other insects in, and possibly allowing the beetles to escape. Securing the netting at the bottom of the pot was an issue as well. The twine seemed to be a great solution that we will use next year.
Water access is of great importance. The level of effort going into watering of the nurseries was greatly exasperated due to the conditions. The watering can had to be filled from a spigot off the water fountain in Kingsley Park, which was slow and cumbersome due to the level of the tap from the ground. During the heat of the summer and the height of the growing season, watering would take up upwards of 1 hr each day. Access to a better watering system will be very important to the program's success.
It might be worthwhile to create a structure that would hold the loosestrife plants up against the wind. During several rain storms, winds knocked the plants over, tearing the netting and upending the dish pans.