(09/26/18) BATON ROUGE, La. — LSU AgCenter scientists conducting research on Roseau cane scale said a recent study showed this insect has not attacked commercial crops or marsh grasses important to Louisiana.

The scale could be one of the culprits causing die-off of Roseau cane in marshes within the lower Mississippi River Delta.

AgCenter entomologist Rodrigo Diaz said farmers were concerned that the scale may also find its way to grass crops.

Leslie Avilés, an entomology graduate student working with Diaz, conducted studies in the greenhouse and in the field on 17 types of grasses including agronomic crops sugarcane, corn, rice and sorghum and native marsh plants smooth cordgrass and California bulrush.

Avilés planted stems from each individual grass in containers. She also added a stem of Roseau cane heavily infested with the scale to each container and tied the stems together.

“For the experiment, we collected infested Roseau cane from the Mississippi River Delta,” Avilés said.

She also included scale-free Roseau cane in a container with infested cane as the control.

After a month she checked the stems for infestations.

The first generation of the scale is called crawlers. Avilés said they hatch and attempt to move to a new stem to infest.

Avilés found crawlers on bulrush and cordgrass. They had attempted unsuccessfully to settle on those native grasses but did not mature into adulthood. No crawlers were found on the commercial crops.

“Our studies show that the scale was not a threat to agronomic crops and appears to be restricted to Roseau cane,” Diaz said.

Avilés also went to the mouth of the Mississippi where heavy infestations are found to see if the scale was infesting native grasses in the marsh.

“We found native grasses growing next to heavily infested Roseau cane,” Avilés said. “We peeled back hundreds of samples from several species of marsh grasses and searched for the scale but didn’t find any.”

Diaz said several state agencies, including the Louisiana Department of Agriculture and Forestry and the Louisiana Department of Wildlife and Fisheries, were interested in this study.

These results are good news to LDAF personnel because Louisiana farmers already have numerous pest issues that significantly effect crop yields and quality. LDAF implemented a quarantine that restricted movement of infested Roseau cane to mitigate movement of the pest across the state.

LDWF uses smooth cordgrass and bulrush in coastal restoration projects, and this information supports the continuation of that work. Also, agents with LDWF have been instrumental in getting Diaz and his researchers into areas in the marsh where scale infestations are prevalent.

“The logistics of getting to these locations is complicated,” Diaz said. “Typically, we are taking a boat ride for an hour to remote places of the Mississippi River Delta.”

Diaz said these marshes are vitally important to the ecology and economy of Louisiana.

LSU AgCenter associate vice president Rodgers Leonard said these research efforts are offering initial information about the biology and ecology of this pest, which can be used to better understand the impacts on Louisiana’s natural resources and provide the basis for future management tactics.

Leslie Avilés, an LSU graduate student in entomology, inspects Roseau cane that is part of plant host experiment she conducted at a greenhouse on the LSU campus. Avilés was looking to see if Roseau cane scale would infest commercial crops or marsh grasses important to Louisiana. Photo by Tobie Blanchard/LSU AgCenter

Leslie Avilés (left), an LSU graduate student in entomology, and Madeline Gill, LSU AgCenter entomology research associate, inspect stems of Roseau cane in the Mississippi River Delta as part of a plant host study. Photo by Rodrigo Diaz/LSU AgCenter