Final Report
Pseudoscymnus tsugae Release
Hemlock Gorge 2001-2005
Background:
The Department of Conservation and Recreation (DCR) (formerly the Department of Environmental Management) was approached by the Friends of Hemlock Gorge regarding the possible release of the predatory ladybird beetle (Pseudoscymnus tsugae) for the control of an infestation of Hemlock Woolly Adelgid (HWA) (Adelges tsugae) at the Hemlock Gorge in Newton. A site visit was conducted with the USDA Forest Service to determine if the site met the federal release criteria. It was determined that the site did not meet these criteria because of extremely high HWA populations. Through the efforts of The Friends of Hemlock Gorge a $60,000 earmark was included in the Metropolitan District Commission’s (MDC) state budget to purchase the predatory beetles. This money was transferred to the Department of Conservation and Recreation’s budget because the MDC lacked the necessary resources to release and monitor the beetle release. Three releases were conducted in 2001 and 2002 as indicated in the chart below.
| Release Date | Quantity | Source |
|---|---|---|
| May 2, 2001 | 5000 Adult | NJ Dept of Agriculture |
| June 6, 2001 | 5000 Adult and Larvae | Ecoscientific Solutions |
| May 16, 2002 | 5011 Adult | Ecoscientific Solutions |
| Total | 15,011 |
Procedure and Data
The DCR determined that the most efficient way to monitor these release was to follow the federal guidelines even though no federal money was involved in the release.
The results of three years of monitoring are presented below.
| Date | HWA Density | Hemlock Health | No. Adults | No. Larvae |
|---|---|---|---|---|
| June 6, 2001 | High | Fair | 15 | 0 |
| July 25, 2001 | High | Fair | 23 | 1 |
| August 16, 2001 | High | Fair | 30 Plus | 0 |
| Sept. 18, 2001 | High | Fair | 1 | 0 |
| May 17, 2002 | High | Fair | 3 | 2 |
| June 27, 2002 | High | Fair | 12 | 1 |
| July 25, 2002 | High | Fair | 7 | 0 |
| August 23, 2002 | High | Fair | 4 | 0 |
| June 27, 2003 | Light | Fair | 0 | 0 |
| July 31, 2003 | Light | Fair | 0 | 0 |
| August 14, 2003 | Light | Fair | 0 | 0 |
| June 17, 2004 | Light | Good | 0 | 0 |
| Sept.21, 2004 | Light | Good | 0 | 0 |
| Sept 28, 2005 | Light | Good | 0 | 0 |
Conclusion:
The predatory ladybird beetle Pseudoscymnus tsugae in considered to be established at the Hemlock Gorge in Newton. This conclusion was reached because the beetles were recovered in the year following a release and immature beetles were also collected, which indicates the presence of a breeding population. Several adults were collected 75 feet from the original release site. I firmly believe the beetles are still present at the Hemlock Gorge, but because of the reduction of the HWA population the beetles were forced to disperse greatly in search of food. The other factor that has hindered our ability to locate them is the fact that there are a limited number of live hemlock branches reachable from the ground to sample.
The health of the hemlocks appears to be improving as indicated by an improvement in the color of the foliage and the presence of new growth. A combination of several factors is responsible for this improvement:
- Extremely low temperatures during the winter of 2002-03 resulted in as much as 90% mortality of the adelgid population.
- The large amount of moisture we received during the 2003 growing season.
- The presence of the ladybird beetles.
During this past fall I spent considerable time at the Gorge attempting to recover beetles. These efforts were not productive. I am however convinced that the beetles are still present. I also noted that many of the trees were producing new growth and that on some of this new growth immature HWA was observed.
I will continue to make yearly visits to the Gorge of observe the condition of the hemlocks and hopefully recover the predatory ladybird beetles.
Charlie Burnham