DEPARTMENTS


Plant Health



EAB detected in Connecticut


Emerald ash borer has moved into Connecticut.
Photo courtesy of David Cappaert, Michigan State University; Bugwood.org
Emerald ash borer has been confirmed in Connecticut for the first time, making the state the 16th to report infestation. Connecticut Agricultural Experiment Station officials detected EAB in Prospect, and the pest was positively identified by USDA APHIS Plant Protection and Quarantine officials. According to the state's Department of Energy & Environmental Protection, insect specimens were recovered from a ground-nesting native wasp (Cerceris fumipennis), a natural predator of EAB. Three additional borers were captured in traps in Prospect as well as Naugatuck; the towns are located south of Waterbury in the west central part of the state. Although unconfirmed at press time, it is believed EAB also may be present in Naugatuck State Forest.

Connecticut has an estimated 22 million ash trees, comprising between 4 and 15 percent of the state's canopy. Until now, the nearest known infestation was located in eastern New York near the Hudson River. State officials expressed concern that the pest may have been moved into the state with infested firewood.

Beetle evolves rapidly to control invasive tree


The tamarisk leaf beetle (Diorhabda carinulata), introduced to control invasive tamarisk, has been found to change its life cycle to more efficiently consume the plant.
A beetle introduced in 2001 to control invasive tamarisk has proved not only to be effective against the plant, but appears to be changing its life cycle to more effectively consume the weed. Researchers at the University of California-Santa Barbara tested the tamarisk leaf beetle (Diorhabda carinulata) as a biocontrol agent for nearly a decade before setting it loose on the invasive shrub, also known as saltcedar. The plant was introduced to the U.S. from Eurasia in the 1800s, but rapidly established itself in riparian areas and outcompeted native vegetation for precious resources. In addition to its invasive characteristics, saltcedar is highly flammable even when green and healthy.

Once released, the tamarisk leaf beetle established itself quickly in northern regions of the U.S., consuming only the foliage of tamarisk and hibernating in the plants' leaf litter. In southern regions, however, the beetle struggled with shorter day lengths during its reproductive season; the disparity fooled the critter into entering hibernation early and caused it to use up its metabolic reserves before the arrival of spring - resulting in death.


UC-Santa Barbara researcher Tom Dudley and a tamarisk plant.
Photos courtesy of UC Santa Barbara unless otherwise noted.

About seven years after the introduction, however, researchers discovered that beetles in the southern region had succeeded in adjusting their hibernation time, making it easier for the newer generation to survive the season. According to the university, "Between 2003 and 2008, for instance, tamarisk leaf beetles at eastern Colorado's Arkansas River went from going dormant in late July to remaining active until mid-August. 'This has resulted in the first successes for the biocontrol program for tamarisk in Colorado's Arkansas River Basin,' said [researcher Dan] Bean, who is now with the Colorado Department of Agriculture. The same genetic mechanism also made it possible for the insect's continued southern dispersal, and further biocontrol of the invasive tamarisk."

Tom Dudley, principal investigator at UC-Santa Barbara's Marine Science Institute Riparian Invasive Research Lab, called the find " ... one of the clearest cases of rapid evolution." The same genetic mechanism has made it possible for the beetle to establish a stronger presence in the south, thus expanding biocontrol of the invasive tamarisk.

"It's a very cost-effective way of containing the weed," Dudley explained. In some cases, he added, natural vegetation once nearly eliminated by saltcedar will be able to reestablish itself. Total elimination is not the goal, however, as tamarisk has had nearly 200 years to settle in and become part of the ecosystem.

And fears that the tamarisk leaf beetle may tire of saltcedar and move on to other tasty and valuable plants are unfounded, according to Dudley. Many years of testing have shown that the bug feeds and reproduces only on tamarisk. Close observation also revealed that the beetle's population experiences a gradual dieback as its food source decreases. It also has become a part of the ecosystem, providing an additional source of food for birds and other predators.