Invasive species affecting growers

Published: November 16, 2011

Invasive species in South Florida eventually become a threat to agriculture. Some of them have already spread to other parts of Florida.

Giant African land snails discovered in Miami-Dade County neighborhoods in September cause plant damage and eat stucco and plaster. The snails can also carry a virus that can cause meningitis in humans.

“The giant African land snail has not been found in any fruit orchids or plant nurseries, but the infestation is getting close to the agricultural areas,” said Adrian Hunsberger, urban horticulture agent and entomologist with the University of Florida’s IFAS Miami-Dade County Extension office. “The USDA and the Florida Department of Agriculture are doing a lot of inspections and are trying to eradicate the snail.”

The snail is originally from East Africa and is one of the most damaging land snails in the world. They eat at least 500 different types of plants and can grow up to eight inches and live for nine years.

“The … snail has no known predator so we have to eradicate this, and it takes considerable time … but we feel confident that we would be able to reach eradication,” said Mark Fagan, spokesman for the Florida Department of Agriculture and Consumer Services.

In Miami-Dade County, another invasive species is the redbay ambrosia beetle that affects fruit growers.

The invasive insect causes the laurel wilt, a fungal disease thataffects trees of the laurel family. The disease is killing swamp bay trees.

“The disease is here and is killing our native trees,” Hunsberger said. “A lot of red bay trees in the state of Florida are dying from the disease.”

According to Hunsberger, avocado trees haven’t been affected — yet.

“The avocado growers are very worried about the disease because most of the commercial avocados are grown in Miami-Dade County and it could be devastating to the industry,” Hunsberger said.

An invasive species affecting Miami-Dade citrus growers is the Asian citrus psyllid. The insect carries the greening disease, which damages citrus trees.

“Our goal is to try to work it out to control it and manage it,” said Fagan. “The psyllid infects the tree with the disease, then the disease is very difficult to diagnose in the field because the symptoms can be a simple nutritional deficiency, or it can be the disease, so we have to get samples from the tree and they can be diagnosed in the laboratory.”

On average, Florida gets one new pest a month.

Fagan said pests are often introduced in Florida unintentionally by travelers because of the proximity to the Caribbean and international trade.

“We are always on the lookout, very vigilant for any number of pests that threaten our agricultural crops, anything that enters the agricultural crops — it’s constantly been looked for,” Fagan said.

Fagan said there is always a possibility that any invasive species in one county can spread to another county.

The bacterial disease of citrus canker was originally found in Miami-Dade County, and now it has spread throughout the state.

Several invasive species are currently in Palm Beach County, including the Sri Lanka weevil.

“The Sri Lanka weevil is affecting large numbers of fruit trees, landscaping plants and the vegetables,” said David Sui, a UF IFAS Extension faculty member on commercial vegetables and tropical fruits at Palm Beach County.

The Sri Lanka weevil affects citrus, lychee, mango and avocado trees.

Another invasive species is the western flower thrips. The insect damages crops such as peppers, tomatoes and eggplants.

“To control the invasive species, there are natural enemies, beneficial insects and the chemical pesticides all help, and you have to use all the approaches to manage it,” Sui said.

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