Roseau cane scale research featured at vegetation managers meeting

Randy LaBauve  |  3/29/2018 7:08:40 PM

(03/28/18) BATON ROUGE, La. — More than 300 commercial applicators met recently for the annual Louisiana Vegetation Managers Association meeting — a session designed for their license renewals. It was also a chance for them to learn about current science on topics like Roseau cane scale and consider tips on being effective and safe in their industry.

LSU AgCenter entomologist Blake Wilson discussed current research on invasive scale insects and their possible effects on Roseau cane, an important wetland plant that helps prevent coastal erosion. Die-off of these deep-rooted grasses is presenting a significant challenge to coastal restoration efforts in some parts of the state.

The Louisiana Department of Agriculture and Forestry issued an emergency quarantine for Roseau cane in certain parts of the state effective March 26.

“Last year there were enormous scale population spikes in the summer. As many as 800 to 1,000 were seen on a single stem,” Wilson said. “Elephant ear, hyacinth and giant salvinia are taking the place of Roseau cane once it dies out.”

Control of the scale, an invasive species from Asia, presents a big challenge because of its limited exposure to any foliar sprays. Almost every product has restricted use for aquatic systems, Wilson said.

“Insecticide research is a problem because these products could have widespread detrimental effects on speckled trout, redfish, shrimp and oysters,” he said.

“We’re looking at systemic applications to treat roots, but insecticide work may not be feasible,” he said. “Factors other than scale may be involved in the Roseau cane die-offs as well.”

Wilson cited a study of a globally distributed grass that died off in Europe during the 1990s. The research found runoff, pollutants, diseases and insects all contributed to plant death.

The scale could potentially damage crops like rice, sugarcane and soybeans, Wilson said. AgCenter researchers are testing crop varieties to see their potential risk to scale infestation.

“This invasive species is not supposed to be in North America,” Wilson said. “Not much is known about it, but once they are attached to the plant, they stay there the rest of their life while sucking juices from it.”

The Louisiana quarantine is an attempt to limit the spread of the insect by boat and is in effect for parts of 11 parishes and the entirety of 26 other parishes.

More information on the quarantine and parishes effected is available online at http://bit.ly/2Ihrqfw.

“Lower Plaquemines Parish has the most reported Roseau cane die-off,” Wilson said. “Scale doesn’t fly, so it can be moved by boats and by moving Roseau for duck blinds. So it’s important to clean your boats.”

More information on AgCenter Roseau cane die-off research is available online at http://www.lsuagcenter.com/roseaucane.

AgCenter pesticide safety education coordinator Kim Pope spoke about paying attention to details in spraying herbicides effectively and safely.

“The problem with these products is that they’re susceptible to volatility,” Pope said. “Bigger droplets are better, and smaller droplets are worse for dicamba drift.”

Some important steps are cleaning tanks well, properly adjusting nozzle size and using large enough buffer zones, she said.

“When do you no longer have control? After it comes out of the nozzle,” Pope said. “If you don’t set it up for success, you have a problem.”

Jay Grymes, an AgCenter adjunct climatologist, emphasized the importance of having large enough buffer zones around application sites and understanding the impacts of temperature inversions and chemical drift.

“A temperature inversion is defined by a layer of warmer air sitting above cooler air, creating a stable atmosphere,” Grymes said. “The inversion acts like a lid, causing suspended spray plumes to drift horizontally, potentially impacting areas around the intended target.”

Typically, unstable air is good for spraying and stable air is not good for spraying, Grymes said.

Chris Mudge, a research biologist for the U.S. Army Engineer Research and Development Center and adjunct professor in the AgCenter, addressed whether it is beneficial to have a weed management program during winter, usually a down time for spray crews.

“It’s worth spraying even when you think plants are dying,” Mudge said, referring to his research on killing invasive plants like giant salvinia with a low-volume herbicide mix.

“You can’t just shut down for winter on invasive species,” he said. “If there’s a mild winter or you start too late, you get reinfestation.”

“Aquatic herbicides can be effective agents against salvinia prior to winter and freeze events,” he said.

The AgCenter is screening the cold tolerance of the salvinia weevil, an insect that consumes the giant salvinia plant.

Dennis Burns, an AgCenter agent in Tensas Parish, discussed the complexities of using unmanned aerial vehicles for precision agriculture.

“To use drones in agriculture, you have to be certified and to have a Federal Aviation Administration operator’s license,” Burns said. “It’s not easy to get your license. There are regulations you need to follow, such as preflight inspections, and you need to be able to respond to an in-flight emergency.”

The Louisiana Vegetation Managers Association is composed of professionals from the LSU AgCenter, Louisiana Department of Agriculture and Forestry, and Louisiana Department of Transportation and Development along with members of the chemical industry and commercial applicators.

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Small insects called scales infest a Roseau cane plant in Plaquemines Parish. The invasive species that originated in Japan and China has killed large stands of Roseau cane in Louisiana. Photo by Rodrigo Diaz/LSU AgCenter



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Rachel Harman, an LSU graduate student, is surrounded by dead Roseau cane stalks as she examines a section of live cane to see if any scale insects are present. Photo by Bruce Schultz/LSU AgCenter

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A pond infested with giant salvinia is seen during a workshop on using salvinia weevils to control the invasive aquatic weed at the LSU AgCenter Reproductive Biology Center in St. Gabriel. This “rearing pond” is used to grow the weed and weevils. The yellow boom pushes the weed closer to the shore so it is easier to harvest samples. Photo by Olivia McClure/LSU AgCenter

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