Beetle Monitoring

2007 & 2008 Critical Monitoring of Tamarisk
Biological Control Activities in Eastern Utah & Western Colorado

Background

Biological control, or bio-control, uses specific organisms to control an undesirable organism, in this case tamarisk. The tamarisk biological control agent, Diorhabda elongata, is providing an active 670 mile experiment along the Colorado, Green, and Dolores Rivers. D. elongata, or the tamarisk leaf beetle, works to control tamarisk by repeatedly defoliating the plant over several years.

Preliminary evidence of effectiveness shows great potential. If this bio-control project continues to progress, it could be used as one of the main mechanisms for tamarisk control and maintenance. If this is the case advantages over other approaches are significant; i.e., limited use of herbicides and a cost-effective long-term solution. 

Monitoring these beetle populations is critical to provide insight and data on their direct and indirect impacts on the riparian ecosystem. In 2007, the Tamarisk Coalition, in partnership with the Palisade Insectary, identified the need for this immensely important activity and made the decision to initiate beetle monitoring efforts on the Colorado and Green Rivers.

• 2008 Diorhabda elongata Distribution Map
• 2007 Colorado River Beetle Distribution Chart
• 2008 Dolores River Beetle Distribution Chart
• National Park Service Investigator's Annual Report (IAR)-2007 Monitoring

The Coalition’s 2008 monitoring program is part of a 5-year effort to support a body of knowledge that will determine the efficacy of the beetle, Diorhabda elongata, as a tamarisk bio-control agent on these three river systems. The goals of this monitoring program are -

1. To obtain data concerning the dispersal and establishment of D. elongata;
2. To measure the efficacy of the beetle in controlling tamarisk;
3. To monitor the rate of tamarisk mortality;
4. To identify the response of beneficial native vegetation and of non-beneficial weedy species to tamarisk bio-control.

Monitoring Protocols

Data is collected during the summer months via raft every kilometer on -

1. The Colorado River from Loma, Colorado to Lake Powell at Hite Bridge, Utah (317 km);
2. The Green River from the tail water of Flaming Gorge dam in Wyoming to the Colorado River confluence in Utah (463 km);
3. The Dolores River from the tail water of McPhee Reservoir dam in Colorado to the Colorado River confluence in Utah (295 km).  A portion of the Dolores River is monitored via vehicle access. 

Seventy percent of these waterways run through Utah. The remainder are in Colorado.

At each collection site field crews conduct 20 consecutive bug net sweeps on a minimum of 5 different trees. When fewer than 5 trees are present 20 sweeps are conducted on what trees are present. When no tamarisk tree is present at a kilometer mark, the crew travels to the next available set of tamarisk and sweeps there. After such an unscheduled sweep, the crew resumes monitoring at the next pre-scheduled kilometer mark even if it is not a full kilometer from the previous sweep spot.

After each set of 20 sweeps, adult beetles and larvae are counted and adults are sexed. At each site a GPS point is taken and the following information is recorded -

Date Number of each sex Kilometer number

ID number of GPS point Photo numbers Additional notes

If beetle numbers are overwhelming, that is 40 or more adult beetles in a sample, then 40 beetles are sexed to acquire a general idea of the population’s sex ratio.

Beetle induced defoliation levels of the tamarisk trees themselves are also be ranked as -

• Light - less than 20 percent
• Moderate - 20 to 50 percent
• Heavy - 50 to 100 percent

Tamarisk defoliation is recorded as percent of plants within a 10-meter radius of the monitored site. Additionally, within this 10-meter radius other vegetative species are identified and their densities noted. Due to the extensive nature of this monitoring effort, it is important to collect the necessary information quickly. Therefore, surrounding vegetation are identified by sight only.

To increase the accuracy of this data collection, likely species to be encountered were identified with the aid of a botanist familiar with the ecosystem. These species include natives such as three-leaf sumac, four-wing saltbush, rabbitbrush, oak brush, sage, currants, bunchgrasses, salt grass, box elder, willow, and cottonwood; and non-native invasives: cheatgrass, perennial pepperweed (tall whitetop), knapweed, whitetop (hoary cress), Russian thistle, Russian olive, and kochia. If present, densities of each species are recorded as light (less than 20 percent), moderate (20 to 50 percent), or heavy (50 to 100 percent).

Safety

Established safety protocols are followed for both river and camping safety. Two-person field crews have at least one technician certified in Wilderness First Aid on all trips. Appropriate river use and research permits have been acquired from both the BLM and National Park Service (BLM permit # J-381, NPS permit # 51838). Additionally, all field crews follow Leave No Trace practices to minimize their impact on the riparian corridor.