MSU scientists urge farmers to scout for new invasive pest

RAYMOND, Miss. -- Although pasture mealybugs have not been detected in Mississippi, entomologists and forage specialists at Mississippi State University urge farmers to frequently scout their pastures for signs of the invasive pest.

“We can’t definitively say we don’t have it here. It could be here. We just haven’t detected it yet,” said Zia Williamson, an entomologist with the MSU Extension Service who specializes in forages, turf and ornamentals. “We feel it is likely just a matter of time until we do find them because they move so easily from one place to another.”

The pasture mealybug, known by its scientific name Heliococcus summervillei, can quickly damage and eventually kill pastures and hay fields if undetected. They can spread to new areas by such ways as the movement of hay or by wind.

“It is very important to catch this pest early, especially in pastures and hay fields because forage and hay production can be devastated if the pest is allowed to multiply. If your field is killed by the pest, you’re looking at two years to fully reestablish those fields,” Williamson said.

The pest was first confirmed in the U.S. in Texas in fall 2025 and has since been found in Louisiana and Florida. MSU Extension specialists are collaborating with specialists in all three states to understand more about the pest’s behavior and effects in the U.S.

These pests feed on warm-season grasses and prefer the habitat of pastures and hay fields with a dense, thick canopy but also can be found in turf. Populations can multiply rapidly when humidity and temperatures are high and rainfall increases.

Some of the forage species that can be impacted in Mississippi include bahiagrass, bermudagrass, Johnsongrass, crabgrass, sorghum-sudan grass and some species of blue stem.

Williamson said producers should scout their fields as often as possible. Specialists with Texas A&M Agrilife Extension have noted that symptoms of mealybug feeding can show up within a week, but complete dieback could take longer.

Producers should remember the acronym PMB when looking for signs of pasture mealybug presence, Williamson said.

PMB stands for purpling, messiness and bareness. Early signs of infestation are grasses that go from yellow to purple or red. This discoloration is caused by a toxin in the pest’s saliva that weakens the plant’s defenses, making it susceptible to diseases. 

The field can look messy from the actual presence of the mealybugs, which can resemble small pieces of white lint, as well as honeydew secretions of the mealybugs that cause sooty mold, a fungus that coats the plant and blocks photosynthesis. Bare spots will also begin appearing because of pasture dieback caused by weakened plant defenses.

Pasture mealybugs are oval with a white, waxy coat. Adult females are 2 millimeters to 5 millimeters in length. Older mealybugs will have white hairs all over their bodies. The nymph stage is what feeds on grass and causes the damage. The smallest of the nymphs measure less than 1 millimeter and can only be seen with a magnifying glass.

Pasture mealybugs can be found at the base of plants, in the roots, just under the soil surface and under cow patties.

Rocky Lemus, an MSU Extension forage specialist, said routine scouting and proper identification of the pest is vital to successful management.

“It is very important to keep an eye on areas that are dying in the pasture and scout the areas surrounding the affected area,” Lemus said. “This pest can affect over 590,000 acres in bermudagrass and over 1 million acres in bahiagrass in Mississippi.”

According to observations in Texas, even small mealybug populations can do large amounts of damage if weather conditions are right.

“This pest has the potential to be economically devastating for both hay and livestock producers because you can’t market hay you don’t have and you can’t graze your livestock in a pasture that has been killed,” Williamson said.

Reestablishment of pasture and hay fields requires complete biomass removal, including burning, followed by strategic forage selection because the pasture mealybug can survive deep within the soil or root zones. Producers will then need to replant with forage species, such as tall fescue and pearl millet, that are not susceptible to the mealybug.

“There is still very little information on how other summer annuals such as forage sorghum and sorghum-sudan hybrids can be affected,” Lemus said. “Deep disking might be needed since tillage disrupts the soil structure, exposes the root-dwelling pests to environmental elements and enhances any residual control measures.”

While pasture mealybugs prefer tropical and subtropical grasses in a pasture setting, they have been found feeding in turfgrass in Texas, Louisiana and Florida.

“They are less attracted to well-managed lawns and other turf, as they prefer the environment created by a thick canopy like you would find in a pasture or hay production setting. If you’re mowing regularly, they are less likely to attack your lawn,” Williamson said.

“They are hearty and spread easily, which makes them difficult to deal with. They are also new to the U.S., so we don’t have a lot of the information yet that we need to be able to understand them and help producers defend against them.”

In Mississippi, producers have one approved insecticide -- Sefina Inscalis -- that has shown the ability to suppress low populations caught and treated early.

A Section 18 Emergency Exemption has been filed with the Environmental Protection Agency for Centric 40WG, which has been successful in reducing populations in Texas. But there is no clear timeline for when or if the exemption could be approved.

First discovered in Australia in 1928, pasture mealybug was found in the Western Hemisphere between 2019 and 2020 in the Caribbean.

The pest was first confirmed in the U.S. in Texas in fall 2025. It was found in Louisiana sugarcane fields later in 2025. Florida officials detected the tiny pest in limpograss fields. It was also found feeding on the edges of corn fields earlier this year in Florida, Williamson said. 

“We don’t know if or how much of a problem they will be in corn, but they have been shown to incidentally feed on it,” Williamson pointed out. 

Williamson said producers who suspect they have found pasture mealybug should contact their MSU Extension agent. 

“The sooner we can positively identify any presence of pasture mealybug in the state, the better off we will be,” she said.

Texas specialists recommend the following guidelines when scouting fields:

• †Concentrate on areas with early symptoms, including yellowing, purpling or reddening and poorly growing grass.
• †Check the edges of damaged patches instead of the middle of dying areas.
• †Look for mealybugs on the undersides of leaves, especially lower leaves.
• †Check the soil surface and thatch below the grass canopy for mealybugs.
• †In hay that is 14 to 30 days post-cutting, pull the grass stem back at the soil surface and look for mealybugs congregated on the stem just below the soil surface.
• †Mealybug size ranges from less than 1 millimeter to 5 millimeters in length. If larger-sized mealybugs are present, be aware that many more tiny and nearly undetectable nymphs may be present.

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