Podcast (podcast_associations): Play in new window | Download (Duration: 4:01 — 5.5MB) | Embed

Subscribe Email | TuneIn | RSS

Welcome to The Turf Zone podcast. This episode features the article “Dig into Ground Pearls: Investigating Thresholds and Distributions of a Spreading Pest Complex” written by Lily Deeter, Peter Hertl, and Terri Billeisen.

Ground pearls (Hemiptera: Margarodidae) are severe insect pests of warm season turfgrass in North Carolina and much of the southern United States, spanning from Florida to California. These scale insects feed on grass roots fluids, causing distinctive circular dead patches turfgrass and frustration in homeowners, superintendents, and sod producers. No currently registered insecticides have shown consistent control for ground pearls (Chong, 2018; Thomson et al, 2021), likely due to their wax-protected cyst, the immature nymph stage that feeds on plant roots with piercing-sucking mouthparts. In addition, their subterranean habit and ability to remain encysted for years under adverse conditions make management of this insect challenging. As an insect family with over 100 species, ground pearls cause damage beyond managed turfgrass. Additional affected crops include grapevines in South Africa, wheat and barley in the Middle East, and sugarcane in Australia (García Morales et al., 2016).

Two distinct ground pearl species infest North Carolina turfgrass: Eumargarodes laingi, known as the “pink ground pearl,” and Dimargarodes meridionalis, which is orange in the adult female life stage. While E. laingi cysts are typically a dull brown, beige, or pink, the cysts of D. meridionalis are shiny yellow, orange, or white. In North Carolina, these two species occur both separately and together in mixed infestations.

As part of my dissertation research at NC State, I am investigating the ground pearl species complex and using distribution and life staging specifics to inform management. Understanding species abundance and impact may influence control approaches including product selection or timing. Greenhouse trials are ongoing to investigate and establish damage thresholds in centipedegrass, the most susceptible turfgrass species to ground pearl damage. Adult female ground pearls were introduced to potted grass containers at different densities and species combinations. Time to damage incidence is recorded as females lay eggs and establish a new generation of cysts. Damaged surface area will be estimated by individual container images using ImageJ software that quantifies green pixelation in each image. Containers are photographed every other week in a photo tent to maintain consistent lighting. Results from this study will inform not only damage potential of each ground pearl species, but also the damage and tolerance thresholds when managing infestations.

I am also actively collecting distribution data for both species within and beyond the state. Once believed to be a localized issue, ground pearl infestations have now spread across most of the Coastal Plain and well into the Piedmont. Infestations of D. meridionalis are typically found in mixed infestations with E. laingi along the coast, while E. laingi infestations are spreading west as far as Wake County. Distribution data is growing through collaboration with extension agents, homeowners, and the NC State Turfgrass Diagnostics Lab.

While I continue to characterize impact in North Carolina, my research on ground pearls will also investigate new pesticide formulations and emergence cycles to improve product application timing. I am also studying the evolution of this pest family using phylogenomics. Results from this research will help refine management procedures for ground pearls in North Carolina turfgrass and beyond.

You have been listening to The Turf Zone Podcast. Follow The Turf Zone on X, Facebook and LinkedIn for all things turfgrass, featuring podcasts, magazines, events and more.