Understanding Emerald Ash Borer Traps for Detection and Management

Understanding Emerald Ash Borer Traps

The emerald ash borer (Agrilus planipennis) is an invasive beetle that has become a major threat to ash trees in North America. Native to Asia, this insect was first discovered in southeast Michigan in 2002. Since then, it has spread rapidly and caused widespread ash tree mortality.

Adult emerald ash borers are slender green beetles that are typically around 8.5 mm long. The larvae are worm-like and spend their time feeding on the inner bark of ash trees, disrupting the tree's ability to transport water and nutrients. This eventually leads to canopy dieback and tree mortality.

Due to the significant ecological and economic impacts of the emerald ash borer, early detection and monitoring of this pest are crucial. One of the main tools used for this purpose is the purple prism trap, which helps survey and detect emerald ash borer populations.

How Do Emerald Ash Borer Traps Work?

The standard emerald ash borer survey trap is a purple prism trap that hangs vertically from a tree branch. The outside is a three-sided prism wrapped in galvanized sheet metal painted purple. The interior contains two cross vanes coated with sticky glue.

Emerald ash borers are attracted to the color purple and the vertical silhouette of the prism trap mimics a tree trunk. As adults fly toward this visual stimulus, they become caught on the sticky glue vanes inside the trap.

Traps are placed in ash trees from May through August when adult emerald ash borers are most active. They are placed throughout areas of concern at densities of 2-6 traps per square mile. Government workers, field biologists, and citizen scientists can assist with deploying and monitoring the traps.

Benefits of Using Emerald Ash Borer Traps

There are several key benefits to using emerald ash borer survey traps:

• Early detection - Traps allow for detection of emerald ash borer infestations before symptoms appear in ash trees. This enables rapid response efforts to contain outbreaks.
• Delineating range - Systematic trapping shows the spread and leading edges of emerald ash borer invasion over time.
• Monitoring - Trapping year after year tracks population trends and the effectiveness of management strategies.
• Public awareness - Engaging the public in emerald ash borer trapping helps spread recognition of this invasive pest.

Interpreting Trap Captures

Checking emerald ash borer traps regularly throughout the summer and recording trap catch data provides important information. The number of beetles found in a trap is relative to the local population density. Higher captures signal areas with intense emerald ash borer infestations.

The absence of trap catches does not necessarily mean emerald ash borer is not present in the area. False negatives can occur due to factors like low insect flight during hot weather or the delayed buildup of populations following initial invasion. But sustained lack of captures in networked traps does indicate isolated infestations outside the wider colonized zone.

Prompt identification of the insects caught in the traps is also critical. Other insects can also be attracted to the visual stimulus of the prism traps. Experts should examine trap catches to confirm the presence of target emerald ash borers and rule out lookalike species.

Limitations of Emerald Ash Borer Traps

While emerald ash borer survey traps are useful detection and monitoring tools, some limitations exist:

• Expense - Purchasing, placing, checking, and processing traps costs time and money.
• Labor intensive - Extensive field work is required to implement trapping across large regions.
• False negatives - Some infested areas can be missed for the reasons described above.
• Trap interference - Human disturbance or wildlife can sometimes disrupt placed traps.
• Non-target impacts - Use of sticky traps risks capturing beneficial insects along with the target pest.

Researchers are exploring ways to optimize emerald ash borer trapping through testing improved lures, trap densities, placement, and design features.

Managing Emerald Ash Borer

In addition to survey trapping, other management strategies are employed against emerald ash borer:

• Regulatory quarantines to slow human-assisted spread
• Removal and destruction of infested trees
• Protective insecticide treatments of high-value ash trees
• Release of predatory wasps that parasitize emerald ash borer
• Planting alternative native tree species in place of lost ash

Ongoing research also focuses on identifying emerald ash borer-resistant ash trees, using visual patterns to mimic unpalatable trees, and employing systemic RNA interference to block essential beetle genes.

Early detection through survey tools like the purple prism trap remains essential to containing new invasions and gathering data to guide management of emerald ash borer. While there are challenges, trapping facilitates targeting resources effectively against a dangerous invasive forest pest.

FAQs

How do emerald ash borer traps work?

Emerald ash borer traps are purple prism-shaped boxes hung in ash trees. The outside is coated in sticky glue. Attracted to the color and shape, adult beetles fly to the traps and get caught on the glue.

When should emerald ash borer traps be placed?

Traps should be installed in late spring through summer when adult beetles are most active and flying, typically May to August.

How often should emerald ash borer traps be checked?

For best results, traps should be checked every 1-2 weeks during the peak activity period. Regular checking allows prompt identification and counting of trapped beetles.

Where should emerald ash borer traps be placed?

Traps should be evenly distributed throughout the area of concern, spaced 2-6 traps per square mile and hung in healthy ash trees about 6-15 feet above ground.

Can emerald ash borer traps completely stop an infestation?

No, traps are used for detection and monitoring - not pest control. An integrated program is needed to fight emerald ash borer infestations.