Sept. 27, 2006

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WESLACO - One of the Lower Rio Grande Valley's most popular landscape plants is under severe insect attack, and the prognosis is not good, according to an expert with Texas Cooperative Extension.

Tiny, white insects inadvertently brought here from Thailand and first found in Florida are decimating sago palms at an alarming rate, said Dr. Boris Castro, an Extension entomologist at the Texas A&M University System Agricultural Research and Extension Center at Weslaco. The palms' survival here is questionable if no action is taken, he said.

"Several state and federal agencies have joined forces to combat this problem, but we're facing an insect that is well established here, is very difficult to manage and is so destructive to sago palms that at this point we're just hoping we can keep the plants thriving here," Castro said.

Efforts include insect surveys, public education in detection and integrated pest management strategies, as well as long-term solutions using bio-control, or beneficial insects to keep populations in check.

Despite their name and appearance, sagos are not a palm but a cycad (pronounced SIGH-kad), among the oldest plants on earth. Originally from East Africa, sagos have remained unchanged for millions of years.

Because of their tropical look, general lack of insect problems and relatively low maintenance requirements, sago palms have always been extremely popular in local landscapes, Castro said.

But sagos may have met their match with the Cycad Aulacaspis scale, a waxy armored insect commonly referred to as CAS, or Asian cycad scales. It is also known as the sago palm scale. They feed on plant juices and literally suck the life out of sagos, he said.

Arriving in Florida in the 1990's aboard a shipment of sago palms from Thailand, and without natural enemies here to keep their numbers in check, their populations increased in Florida, killing sagos and costing millions in losses to the landscape industry and property values.

The Cycad Aulacaspis scale made its way to Texas in 2001, but was not officially reported until 2004. In some areas of the state, including Katy, Houston and College Station, it was found early and contained before it could establish permanent populations.

But the insect has been able to break containment in the Rio Grande Valley. It was first detected here in 2002, became established in 2004 and this year reached outbreak levels, Castro said.

"We're seeing high numbers of insects in Cameron and Hidalgo counties but they also have been reported as established in Hidalgo and Nueces counties," he said. "The highest infestations are in Cameron County, maybe because conditions are more favorable."

The scales' waxy cover makes them practically impervious to many insecticides. That – combined with high reproductive rates and ability to hide in a sago's root system – makes them extremely difficult to eliminate. They can kill a sago in a matter of weeks – if infestations are high enough – then move short distances aboard wind currents," Castro said.

"They feed on plant juices, and once they insert their sucking mouth parts to sago leaves, they remain there," he said. "In heavily infested plants, there might be several thousand insects per square inch draining the life of that plant. The first symptoms a plant will display are yellowing spots on the fronds, or leaves."

That's what Rosie Montano of Harlingen first noticed on the sagos in her yard. "These plants are close to my heart and when I saw them turning yellow, I was freaking out because I knew something was wrong," she said. "Others were completely covered in a white powder and the leaves were dying."

"That's the symptom of heavily infested plants," Castro said. "They look like they've been sprayed with artificial snow."

Montano said she has taken Castro's advice and trimmed the affected fronds, double-bagging them to avoid further spread of the insect. She will soon start a vigorous insecticide spray campaign.

"Populations here have spread far more rapidly than anybody suspected, and they quickly became established here, meaning eradication is not an option," he said. "But we can undertake a management approach that integrates many practices that can be used by wholesalers, retailers and homeowners."

To prevent infestation in landscapes, Castro recommends inspecting both sides of fronds of sago palms before buying them. Make sure they are free of the tiny, waxy rod-like structures or circular, flat scales. If in doubt, call the Extension agent in your county.

Sanitation and inspections are also important.

"Those in the landscaping business should clean pruning and other tools of infested plant material before moving on to new areas or yards. Homeowners should inspect plants weekly to detect infestation. If you see infested fronds, prune affected fronds and dispose of those cuttings in double-sealed plastic bags to prevent re-infestation," Castro said.

Pressurized water wash to dislodge insects is also helpful, provided it is applied to both sides of fronds at least once or twice a week. Regularly applied insecticide sprays can also help.

Castro said several low-cost commercial formulations are available at garden centers, but it is very important to follow label directions to avoid harming the plant.

"Spray oils or insecticidal soaps can be used by homeowners, applied in early morning or late afternoon to reduce the risk of plant burning," he said. "Homeowners can also use products containing acephate or carbaryl-based products. Make sure the insecticide mixture completely covers both sides of leaves until run-off.

"Licensed pesticide applicators can also use products containing dimethoate, pyriproxyfen, dinotefuran or pyrethroids," Castro said. "All of these products are applied to fronds, but dimethoate and dinotefuran can be used as soil drenches to kill populations hiding in roots. Dimethoate may damage new growth."

Castro said several agencies are working to develop both long and short-term solutions.

"We're in the process now of developing educational materials in collaboration with Drs. Carlos Bogran and Scott Ludwig at Texas Cooperative Extension. We also are joining forces with other agencies, including the Texas Agricultural Experiment Station, the Texas Department of Agriculture, the U.S. Department of Agriculture - Animal and Plant Health Inspection Service and the University of Florida to educate the public, survey the severity of the situation and develop long-term solutions such as biological control of this insect," Castro said.

Contact Castro for more information at 956-968-5581.