Center Update: Ground Pearl Control
Evaluation Pesticide Applications to Ground Pearls ( Margarodes spp.) in Centipedegrass
PI: Matthew Martin
The ground pearl (Margarodes spp.), is a subterranean scale insect that infests the roots of turfgrasses and is of major concern to turf managers in Eastern North Carolina and across the southern US. They are typically associated with sandy soils in the coastal plain regions where warm season turf species are grown. Reports of ground pearls as pests occur in Australia, and the southern USA (Allsopp et al. 2000, Buss 2009, Hoffman and Smith 1991). Margarodes species have been identified as pests damaging agronomic crops and turfgrasses in North America, South America, the Caribbean region, Africa, and Southwest Asia (Foldi 2005). However, there is limited information for how ground pearls can be controlled in turf by any management strategy or pesticide. All of the available research suggests that no pesticides or other chemicals are recommended for control of ground pearls. In addition, there are no biological control management techniques currently available for ground pearls (Buss 2008.)
Research on biology and control of ground pearls throughout the United States has led generally to inconclusive results. Some aspects of its biology have been clarified but, in general, its life history remains incompletely understood. The number of ground pearls varies considerably even within infested areas. The quantitative relationship between number of ground pearls present and damage to grass is unknown (C.A. Kouskolekas and R.L. Self). Individual observations over the past 30 years from the principal investigators suggest that ground pearls will attack any perennial grass but are mostly a problem in warm season turf species in North Carolina. This is most likely due to geographic distribution in the eastern region of the state where these grasses are the dominant species. The economic impact to turf managers in infested regions is significant. Centipedegrass (Eremochloa ophiuroides) is highly prone to ground pearl attacks, but St. Augustinegrass (Stenotaphrum secundatum), bermudagrass (Cynodon dactylon), bahiagrass (Paspalum notatum), carpetgrass (Axonopus affinis), and zoysiagrass (Zoysia spp.) can also become infested (Buss 2008, 2009, Hoffman and Smith 1991). Turf areas infected with ground pearls are unable to support plant growth and soil erosion occurs within the damage.
A study was conducted from April 2019 to October 2019 in Wilmington, NC on a common centipedegrass turf area to determine the efficacy of different pesticides for the control of ground pearls. The centipedegrass turf areas was mowed once per week at 1.5 inches and irrigated every other day to prevent drought stress. Treatments were arranged in a randomized complete block design with three replications and applied to 25 ft2 plots. Granular treatments were applied manually with a measured volume in a shaker applicator. All spray treatments were applied using a CO2 powered 4-nozzle boom sprayer with flat fan nozzles calibrated to 87 GPA. All treatments were watered with ¼ inch of irrigation following application. Turf quality ratings were taken monthly. Five soil cores were taken from each plot to a depth of 6 inches using a 3” golf cup cutter at the end of the study to evaluate ground pearl populations.
Results and Discussion
It is important to consider site locations and weather patterns when evaluating ground pearls in turf. 2017-2018 had record rainfall amounts which could have increased turf quality compared to 2019 which had record drought conditions during the spring and summer. Site location also is also critical. The site used in 2019 had a very high number of ground pearls in this particular location which most likely contributed to the low turf quality ratings. Triple Crown plus Cascade had the lowest average number of ground pearls per plot. Acceptable turfgrass quality (>7) was never achieved with any treatments.
Tables 2 and 3 show ground pearl numbers were lower in Triple Crown plus Cascade and Cyonara plus cascade compared to the untreated check. There were no treatments that showed significant improvement in visual turf quality compared to the untreated check. Results from this research indicate that applications of Triple Crown plus Cascade and Cyonara plus cascade could have an effect on ground pearl feeding damage and populations.
Table 1. 2019 Centipedegrass Ground Pearl Plot Treatments
- Divanem (Abamectin) + Revolution
- Zylam (Dinotefuran) + Cascade
- Triple Crown (Zeta-Cypermethrin, Bifenthrin, Imidacloprid) + Cascade
- Merit (Imidacloprid) + Cascade
- Cyonara (Lambda-Cyhalothrin) + Cascade
Table 2. Number of Ground Pearls Collected in Centipedegrass October 15, 2019
|Treatment||Ave no. pearls†|
|Divanem + Revolution||148|
|Zylam + Cascade||163.6|
|Triple Crown + Cascade||57.6|
|Cyonara (Lambda-Cyhalothrin) + Cascade||79.6|
† Units = Average number of ground pearls recovered in five samples per plot using a 3” golf cup cutter
Table 3. 2019 Centipedegrass Turf Quality.
- Untreated 3.0 4.0
- Divanem 3.5 4.5
- Zylam+ Cascade 3.5 4.5
- Triple Crown + Cascade 3.5 5.0
- Merit+ Cascade 3.0 4.5
6 Cyonara (Lambda-Cyhalothrin) + Cascade 3 .0 4.5