FORT PIERCE, Fla. — Because an invasive insect brought the world’s most serious citrus disease to Florida, some growers produce world-class grapefruit inside white mesh screenhouses – a system they call Citrus Under Protective Screen. The screenhouses keep the insect associated with citrus greening from getting on the trees, but producers must manage other pests that penetrate the mesh.

Growers will not face those complications alone. University of Florida scientists working to find Integrative Pest Management (IPM) techniques to manage insects that damage fresh grapefruit inside protective production systems.

“We aim to identify ways to control mites and other pests responsible for crop disease and damage that enter Citrus Under Protective Screen (CUPS),” said Emilie Demard, a Ph.D. graduate with UF’s department of entomology and nematology. “I look at biological control – in this case, predatory mites controlling pest mites to minimize the need for agrochemicals.”

Emilie Demard is a newly minted Ph.D. in entomology and nematology with UF’s Institute of Food and Agricultural Sciences (UF/IFAS). For the last four years, tiny mites have been at the center of Demard’s studies and research. An emerging acarologist — or researcher who specializes in mites —Demard has earned awards at national entomology meetings and a recent international award.

Overseeing Demard’s research is Jawwad Qureshi, associate professor of entomology and nematology at the UF/IFAS Southwest Florida Research and Education Center in Immokalee, Florida. Qureshi funds Demard’s work and is an expert in managing the Asian citrus psyllid, the invasive insect associated with citrus greening, and mites, a second pest of citrus.

“Emilie’s early work to identify natural predators for the control of pest mites in protected production environments contributes to the development of comprehensive IPM models to sustain Florida’s most valuable crop,” said Qureshi.

Demard said screenhouse growers want long-term solutions to control mites and protect the quality of their fruit from unsightly damage.

“We found two mite species: the citrus rust and the citrus red mites inside the protected environment,” she said. “Both damage leaves and fruit, resulting in lower fruit value when sold on the fresh market.”

“Citrus rust mites cause damage to fruit peels called ‘sharking’ or ‘russeting,’ resulting in brown patches. Feeding from citrus red mites creates white to yellow spots, giving a spotted appearance to leaves called ‘stippling,’” said Demard.

“Rust mites are major pests in screenhouses and are hard to control,” said Demard. “Acaracides such as Pyridaben, Fentatin oxide or Abamectin provide some control of mites inside the houses, but the chemicals should not be a long-term solution since mites will eventually become resistant to pesticides.”

Demard’s fieldwork takes place inside four screened structures located at the UF/IFAS Indian River Research and Education Center in Fort Pierce, Florida. Each 58,00 square-feet grow house is 14 feet high. Metal wire rope cables support thick wooden utility poles draped with a 50-mesh white screen. Inside, rows of healthy citrus trees with full canopies rise from pots and the ground, between woven black groundcovers.

“More than 500 acres of screenhouses are in operation in Florida, with new structures ongoing,” said Arnold Schumann, a soil and water science professor at UF/IFAS’s Citrus Research and Education Center in Lake Alfred, Florida.

One important finding Demard made is that the populations of predatory mites increased in the spring during a flush — or when the trees developed flowery, fragrant blooms. The predatory mites use pollen as an alternative food inside CUPS.

“We have not yet discovered effective predatory mites for the citrus rust mite, insects, or fungi to control the two pest mites in screenhouses—but so many researchers work on the problem,” said Demard. “I believe we will find an effective management program for screen grapefruit growers to control citrus red and rust mites.”

Demard’s studies include biological control, pest management, taxonomy, or mite species identification. UF researchers will continue her work for analysis of other factors influencing predatory mite populations, such as ground cover management, canopy volume and alternative food.

Overseeing Demard’s research is Jawwad Qureshi, associate professor of entomology and nematology at the UF/IFAS Southwest Florida Research and Education Center in Immokalee, Florida. Qureshi funds Demard’s work and is an expert in managing the Asian citrus psyllid, the invasive insect associated with citrus greening, and mites, a second pest of citrus.

“Emilie’s early work to identify natural predators for the control of pest mites in protected production environments contributes to the development of comprehensive IPM models to sustain Florida’s most valuable crop,” said Qureshi.

Demard said screenhouse growers want long-term solutions to control mites and protect the quality of their fruit from unsightly damage.

“We found two mite species: the citrus rust and the citrus red mites inside the protected environment,” she said. “Both damage leaves and fruit, resulting in lower fruit value when sold on the fresh market.”

“Citrus rust mites cause damage to fruit peels called ‘sharking’ or ‘russeting,’ resulting in brown patches. Feeding from citrus red mites creates white to yellow spots, giving a spotted appearance to leaves called ‘stippling,’” said Demard. “Rust mites are major pests in screenhouses and are hard to control,” said Demard.

“Acaracides such as Pyridaben, Fentatin oxide or Abamectin provide some control of mites inside the houses, but the chemicals should not be a long-term solution since mites will eventually become resistant to pesticides.”

Demard’s fieldwork takes place inside four screened structures located at the UF/IFAS Indian River Research and Education Center in Fort Pierce, Florida. Each 58,00 square-feet grow house is 14 feet high. Metal wire rope cables support thick wooden utility poles draped with a 50-mesh white screen. Inside, rows of healthy citrus trees with full canopies rise from pots and the ground, between woven black groundcovers.

“More than 500 acres of screenhouses are in operation in Florida, with new structures ongoing,” said Arnold Schumann, a soil and water science professor at UF/IFAS’s Citrus Research and Education Center in Lake Alfred, Florida.

One important finding Demard made is that the populations of predatory mites increased in the spring during a flush — or when the trees developed flowery, fragrant blooms. The predatory mites use pollen as an alternative food inside CUPS.

“We have not yet discovered effective predatory mites for the citrus rust mite, insects, or fungi to control the two pest mites in screenhouses—but so many researchers work on the problem,” said Demard. “I believe we will find an effective management program for screen grapefruit growers to control citrus red and rust mites.”

Demard’s studies include biological control, pest management, taxonomy, or mite species identification. UF researchers will continue her work for analysis of other factors influencing predatory mite populations, such as ground cover management, canopy volume and alternative food.

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