Using community science to explore the spatial distribution of the daylily gall midge (Cecidomyiidae) in Canada’s Maritimes region

Abstract

AbstractThe daylily gall midge, Contarinia quinquenotata (Loew) (Diptera: Cecidomyiidae), is an ornamental pest of daylilies, Hemerocallis spp. Linneas (Asphodelaceae). Originally native to Asia, this pest was accidentally introduced to western North America, and it is believed to occur throughout other parts of North America even though its presence has not been confirmed. Using an online survey of gardeners across Canada’s “Maritimes” (the region that includes the provinces of New Brunswick, Nova Scotia, and Prince Edward Island), we determined that symptoms of the pest occurred at multiple sites across Nova Scotia, but we received no reports from Prince Edward Island or New Brunswick. Sequencing the cytochrome c oxidase 1 gene of the samples submitted by community scientists, we confirmed the daylily gall midge occurs at multiple sites across Nova Scotia. A common garden study that included 517 daylily varieties found that yellow-flowering varieties were almost twice as likely to be affected as nonyellow varieties. Early-flowering varieties were more likely to be attacked than later-flowering varieties. For each day that the date at first flowering was delayed, the likelihood of gall midge attack decreased by 16%. To avoid or mitigate damage where the daylily gall midge occurs, selecting late-flowering varieties with nonyellow flowers can be a useful complement to destructing infested flower buds.