Community of Potential Predators of Hemlock Wooly Adelgid in an

Eastern Hemlock Forest

Wynter Larson

Ossining High School

Review of LiteratureThe hemlock tree is a widely known tree in New England that is heavily infested with the hemlock wooly adelgid (HWA) HWA is an invasive insect from Japan, approximately 1 to 2 mm longMore then 50% of all hemlock trees, in eastern forests, are infested (Martin 2003)

Figure 1.0-Infested Hemlock forest Photo by D.Royle and R.Lathrop

Review of Literature

HWA was first reported in eastern North America in 1951 and by 2002 has spread rapidly across hemlock range (Onken and Reardon 2005) HWA feeds directly on the xylem ray parenchyma cells by inserting a long stylet into the needle cushion (Young et al 1995)

Figure 3.0- Infested hemlock branch

USDA Forest Service

Figure 3.0-Map of HWA infestations and native range in 2003

Image produced by USDA Forest Services

Review of Literature

In China and Japan (native home to HWA) several predators feed on it, whereas in North America the generalist predators fail to keep population reduced (Wallace and Hain 2000)

Major efforts are being put into a biological control because of the lack of sign of long term recovery (Orwig et al. 2002; Ward et al 2004)

Prospects of an infested Hemlock tree surviving more than 12 years are extremely low (Orwig et al. 2002;

Ward et al. 2004)

Introduction

HWA life cycle promotes rapid increase in population

The HWA produces 2 generations a year:1.) Sistens- wingless, hatch in late spring, overwinter (feed and develop in the winter), and survive 9 months 2.) Progrediens- hatch in early spring, both wingless and winged, survive about 4 months

Introduction

Cold winter temperatures play a role in limiting the spread of HWA (Cheah and Shields 2005)

If the temperatures in winter, continue to increase at the rate it is now, the conditions that are currently limiting the adelgid spread will be gone

If nothing is done, the Eastern Hemlock could ultimately disappear from eastern forests within decades (Orwig et al. 2002)

Introduction

Hemlock decline is of great concern because it poses a threat to distinctive habitat, microclimates, and biodiversityHemlock tree plays an important role in forest structure, providing shade and shelter for forest animals (deer, turkey, etc.) Hemlock evergreen cover also impacts abiotic factors such as shade to keep streams cool, which sustains populations of brook trout and many amphibians (Snyder et al. 2002)

Characterized as a foundation species, it creates a local stable condition that is needed by many other species in ecosystems (Jones et al. 1994)

Introduction

Insecticide has shown to have negative side effects in controlling HWA population

Researchers have looked at the potential of the Japanese Lady Beetle, Sasajiscymnus tsugae, as a biological control

Adelgids were 76% less abundant on branches exposed to the lady beetle then those without the beetle (McClure,Cheah 2000)

Purpose

The purpose of this study is three-fold:1.) To quantify the percentage of trees infested with

hemlock wooly adelgid, Adelges tsugae, at Mianus River Gorge Preserve

2.) To test a novel method for canopy sampling for the Japanese Lady Beetle

3.) Quantify potential predators of HWA including: arthropod community, Sasajiscymnus tsugae, Harmonia axyridis, Hippodamia convergens, Chilocorus kuwanae

ScientificScientific

NameName Sasajiscymnus tsugae

Laricobius

nigrinus Hippodamia

convergens Chilocorus kuwanae

Common Common

NameName Japanese Lady Beetle L. Nigrinus

Convergent Lady Beetle

Black lady beetle

Date of Date of

ActivityActivity

(Feeding) (Feeding)

Spring into mid summer

(Attacks progredien generation)

Feed in fall and winter

(winter-active predator)

Spring and summer (if aphids are present)

Mid spring

(when temperatures exceed 50 degrees farenheit)

Introduced and Native Biological Controls to HWA

Methods and Materials

Study Site:Mianus River Gorge Preserve, Bedford, New York Old Growth Hemlock Forest is 100 acres Infested with HWA since 1986 and continues to have annual increases In June of 2000, 2,500 S.tsugae were released on lower branches at plots within hemlock forest

Methods and Materials

A month after the release, a total of 660 minutes were spent monitoring for the beetle using beat sheet method outlined by US Forest Services

A total of 41 beetles were found in this survey

One year later, monitoring failed to detect the beetle in at or near the release site

Study Site Continued…

Methods and Materials

Adelgid Infestation:The level of HWA infestation was surveyed for potential HWA predators at four plots C2, C3, C4, C6

To calculate the percent infestation a modification of a HWA detection method devised by Scott Costa (personal communication Entomology Research Laboratory, University of Vermont) was used

At each site 25 trees were randomly selected

Methods and Materials

Adelgid Infestation:Two branches from each tree were inspected at approximately 2m height and recorded the presence or absence of HWAPreviously trees were sampled in March of 2005 and 2007 to investigate annual changes

Current findings were compared to these previous findings to establish trends in the adelgid population

Methods and Materials Predator Survey:

HWA predators were sampled at the four plots every 3 weeks from April to June using a variation of the sweep net and beating method techniqueA telescopic mesh monarch net was used to sample the canopy at a height between 2 to 8 mInsects were later separated from foliage using filters and a specimen flotation method in water bathsSpecimens were then stored in isopropyl alcohol (85%) for identification purposes

2,500 Japanese Lady Beetles released at MRGP

1986 2000

No sighting of the beetle

Summer of 2008 is when research was conducted

Beetle Recovery-

Only 41 recovered out of the 2,500 released

July 2001

2008

July 2000

Initial infestation at Mianus River Gorge Preserve (MRGP)

Photo: Pennsylvania Dept. of Conservation and Natural Resources

Photo: N.P.S U.S Department of the Interior

Results

HWA infestation was present at all plots in this study and there was an increase at all sites from 2005 to 2007, except at plot C3

The percent increase average for all four plots was 107.5%

The rate of increase varied by plot location and increased at all except plot C3

Results

Potential predators of HWA were not detected suggesting the role of environmental factors

The desired beetles were not recovered in this canopy technique, however other members of the arthropod community were collected and identified to family level

The most prevalent was the oribatid mite

Plot % HWA infestation

in 2005

%HWA infestation

in 2007

Percent

Increase

C2 16 68 325

C3 52 52 0

C4 32 56 75

C6 40 52 30

AVG. 35 57 107.5

Results

Table 1. Plot level analysis of HWA infestation at four plots

Results Prionocyphon limbata (marsh beetle) and Zonantes subfasciatus (ant-like beetles) were found during data collection in June 2008

The spider population, including mites and opilones, were recorded because of findings linking S.tsugae population with the arthropod community in hemlock trees

There was an abundance of oribatid mites which are known to feed on decayed material

Results

Ant-like Leaf beetle- Zonantes subfasciatus

Marsh Beetle-

Prionocyphon limbata

Photos taken by T.Murray 2007

Discussion

Although S.tsugae was not observed and likely no longer present at the gorge, findings show that insects, such as the oribatid mite, may play a role in the presence of the beetle In 2004, Eastern Hemlock was the dominant over-story tree in the preserve, but due to infestation of HWA and EHS decline was expectedDespite the 22 years of infestation, and annual increases, the trees are surviving moderately well showing a persistence of the hemlock forest from an undetermined factor

Discussion

The abundance of mites captured, is evidence to the absence of the beetle If S.tsugae was present, it would have been captured through the sampling method that was used

Limitations to this research include: -no coordinated method in sampling efficacy of the beetle -no way to determine the ultimate factor in the death of hemlock trees in MRGP forest

Discussion

A total of 700 minutes were spent sampling for S.tsugae and none were found, suggesting a failed reintroduction into the forest The original release site of S.tsugae was at Plot C3 and HWA infestation at plot C3 remained the same from 2005 to 2007Future research is needed in order to establish relationship between native predators of HWA

Acknowledgements

I would like to thank my mentor Mark Weckel,from Mianus River Gorge Preserve, for his feedback and supportCarole Cheah, from Connecticut Agricultural Experimental Station, for her advice and ongoing enthusiasm My teachers, Ms.Valerie Holmes and Mr. Angelo Piccirillo, for their guidance and support