Pesticides to treat invasive insect are safe

Says DEM official
Thu, 03/07/2019 - 6:45pm

The State of Rhode Island’s plans for combatting an invasive foreign insect that destroys ash trees should be safe, according to officials, and could involve bio-control agents.

The emerald ash borer, an insect native to Asia, has infested the eastern United States, including Rhode Island, and was first detected in Westerly in June of 2018. Despite that, Tree Warden Ned Phillips said he has “not seen any evidence of emerald ash borer” on Block Island.

Block Island has a population of ash trees, including at Ball O’Brien Park, so while there is concern for their preservation and the environment as a whole, there is also the safety of the children and adults that visit the park to be considered.

Michael Healy, Chief Public Affairs Officer at the Rhode Island Department of Environmental Management, told The Times that pesticides applied by a licensed professional in a controlled manner should be safe, and that bio-control agents could be utilized next year to address the insect’s infestation. The DEM unveiled its action plan on Feb. 22 for attempting to combat the insect, which could involve utilizing insecticides, either through injection of the tree or into the soil beneath it.

Healy said the application of the pesticide should be accompanied by appropriate signage. “As long as it’s applied by a licensed pesticide applicator who applies it in a controlled manner — through injection either in the tree’s trunk or in the soil directly under the tree minimizing external chemical contact — with proper signage posted cautioning the public to applications and dates, yes, it should be safe.”

“Currently, the most effective pesticides for EAB are Imidacloprid, Dinotefuran, and Emamectin Benzoate,” he said, noting that his source for the information was Cliff Sadof at Purdue University. These pesticides “have been proven effective on EAB larvae, with some effect on adults feeding.” (Sadof specializes in pest management of landscape trees, and is co-creator of The Tree Doctor App that helps users diagnose and find recommendations to 175 tree problems on over 60 kinds of trees in the U.S.) 

DEM is also considering the use of bio-control agents to destroy EAB. Biological control is the deployment of the natural enemy of something to destroy it. In the case of EAB, its natural enemy is a parasitic non-stinging wasp, or a parasitoid. Bio-control agents were introduced in the U.S. (Michigan) from China in 2007, and have since been released in 19 states. 

“The best way I can describe a parasitoid,” said Healy,  “is to say it’s where one bug, usually a much smaller bug, stings and paralyzes another bug and effectively hijacks the central nervous system of the second, bigger bug. Usually, it’s a wasp or fly, and there are probably literally tens of thousands of different parasitoids, the parasitoid then lays its eggs on or in the paralyzed body of the host bug, which — voilà! — becomes an all-you-can-eat buffet for developing larvae and ultimately dies.”

“Plans for bio-control agents and release sites for Rhode Island are currently being evaluated by the University of Rhode Island’s Biocontrol Lab,” said Healy, who noted that bio-control agents might be used next year. “The bio-control agents that could be released would be one or both of two parasitoid wasps Tetrastichus planipennisi or Oobius agrili. Both wasps are completely safe and pose no threat to humans or other fauna in our area. They have been rigorously evaluated by researchers from the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service.”

As for the DEM’s overall state action plan, Healy said that since the state “has no plans to treat diseased trees on private or municipal lands, it’s imperative for homeowners to contact a licensed professional arborist to evaluate the ash in their yard and aid in treatment or removal.”

“This is a classic case of an ounce of prevention being worth a pound of cure,” he said. “Ultimately, EAB kills any infested ash tree, and infestations can spread or travel up to two miles a year — much faster when transported by humans in firewood, nursery stock, or ash log products. We urge all Rhode Islanders to help prevent the spread of invasive pests and protect the trees they love by not mindlessly moving firewood.”

For more information go to: DEM’s website contains information regarding EAB: