Ground pearl in turf. 33

What are Ground Pearl?

Ground pearls are underground sap sucking insects, and feed on the roots of turf. This pest has become more of an issue in recent years. Ground Pearl control and treatment is now a problem in sugar cane, vines, grapes, oil palms and turf grass.

• They are a serious pest of turfgrass and in particular of warm season turf on sandy soils.
• The damage they cause is often mistaken for drought stress. It looks like ring-shaped patches of wilting or dead grass.
• These are scale insects in the Margarodidae family, and get their name as they look like pink pearls.
• You tend to see them in the soil or thatch as small pearl-shaped balls.
• The female is pink and has claws and front legs.
• The male is smaller than the female, and has a slender waxy “tail” that is up to 6 mm long.
• The “pink pearl” is the nymph which has a hard, globular, yellow to purple shell. The nymphs are up to 1.5 mm in diameter.¹Buss EA. (May 2009). Insect Pest Management on Turfgrass. EDIS. (29 November 2012)
• This, waxy, spherical shell is what you tend to see.
• Immature first-instar nymphs and cysts (second instars) are when this pest feeds and grows.
• Adult males and females do not have mouth parts and do not feed.

The image below is courtesy of NC State Extension.

What Does Damage Look Like?

• You can see damage from the nymphs as circular patches that look like fairy rings.
• You often see these in dry weather as irregular patches of turf, that turn yellow or brown in the Summer months.
• These patches then either die in the Winter or never green up in the Spring.
• Each year these patches get bigger, and the problem gets worse.

The nymphs extract nutrients from plant roots, and weaken the host plant. If you suspect you have this pest check the boundary between the healthy and chlorotic turf. This is where you will see the greatest numbers of Ground Pearl in turf.²Potter, D.A. 1998. Destructive Turfgrass Insects: Biology, Diagnosis, and Control. Ann Arbor Press, Ann Arbor, Mich..

Biology of Ground Pearl.

• Over the last decade, this pest has become an increasing issue in Australia.
• Turf facilities such as bowling greens, golf clubs and sports grounds have all seen damage.
• The roots of Couch, Buffalo grass, and Zoysia, are often infested with this pest which is easy to see by its pink pearl shape.

Lifecycle.

• The pink females tend to mature in the late Spring and they then emerge from their cysts.
• They then tunnel 50 to 75 mm into the soil, where they then secrete a wax coat.
• Inside this wax coat, they lay up to 100 eggs, and in the right conditions a female may lay eggs several times a year.
• It only takes a few days before the eggs hatch.
• The first instars (crawlers) then move and attack turf roots.
• The nymphs then secrete their outer cover and develop into “pink ground pearls.”
• If conditions are not favourable, female nymphs may remain in the pearl stage for several years.
• They have been known to survive for up to 15 years in the absence of a suitable host³Brandenburg, R. 2003. Don’t give up on ground pearls. Grounds Maintenance. (http://www.grounds-mag.com/mag/grounds_maintenance_dont_give_ground_2)..
• During the Summer and into the Autumn the nymphs continue to develop.
• By the late Autumn or early Winter they have become adults.
• They then spend the Winter inside the cyst (pearl) that surrounds them.
• There is usually one generation each year.
• The life cycle of Ground Pearl in turf is parthenogenic.

Parthenogenesis is a form of asexual reproduction. Offspring can develop from unfertilized eggs, and it has several competitive advantages:

• Rapid population growth.
• A mate is not needed to reproduce.
• Rapid colonisation of new areas.

How do Ground Pearl Move?

• This pest is not very mobile.
• Its small size, and the fact that it lives below the soil surface means that it is unable to move very far under its own power.
• To get to a new site it must dig through the soil. One estimate is that it only moves a maximum of 10 to 15 cm per year⁴Hoffman E, Smith RL. 1991. Emergence and dispersal of Margarodes meridionalis (Homoptera: Coccoidea) in hybrid bermudagrass. Journal of Economic Entomology 84: 1668- 1671..
• This inability to move is key to Ground Pearl treatment.

How To Manage Ground Pearl in Turf.

An integrated program of chemical and cultural control will tend to give the best results.

Cultural Ground Pearl Control.

• Don’t use grass from infected sites. This is important is you intend to establish turf from sod or sprigs.
• Clean all machinery if you use it in infected areas.
• Make sure that the turf nutrition and water do not limit growth. This gives you a better chance to get recovery as fast as possible.
• Use a premium soil wetter such as HydroForce Ultra. If you can move water deeper into the soil profile you get healthier turf. You will also get any chemicals further into the root zone.

In my opinion, the first two measures are the most important.

• They only move 10 to 15 cm a year. If you clean soil from equipment, and do not use infested plant material this will limit its movement.

Chemical Treatment of Ground Pearl.

• One of the issues with Ground Pearl control has been the wax coat on the nymphs.
• This protects them from insecticides once they are inside these pink, pearly cysts.
• The focus of any Ground Pearl treatment must be the adult females and crawlers. This is when this pest does not have this wax cover.

ProForce Scarlet Trio states that when you use it for Ground Pearl control apply it when you detect the adults or crawlers in the early Spring to the end of Summer. This is when they are at their most vulnerable.

Scarlet Trio for Ground Pearl in turf

Research.

• Clemson University found that three months after use, no treatments had an impact on pest levels.
• After nine months, products with the actives Clothianidin (plus a soil wetting agent) and Thiamethoxam did seem to have some efficacy. Clothianidin is one of the key actives in Scarlet Trio.
• Areas treated with Broad-spectrum insecticides tend to have higher numbers of cysts. ⁵https://www.gcmonline.com/course/environment/news/ground-pearls-turf.
• If you maintain a healthy turf cover you will be better able to minimize damage.
• Part of this approach is to limit root damage when you select a pre-emergent herbicide.
• Anything that impacts on healthy root growth. This will worsen the damage from this pest.
• Avoid the use of pre-emergents that can prune roots.