The rapid movement of people and goods invites exotic pests to hospitable Southland. Fight back
Know that irritating little whitefly that’s attacking all sorts of plants in the garden, and the nasty fire ant threatening to take over Southern California yards? How about those pesky rules against transporting fruit and plants across state lines?
What do the two have in common, you ask?
Plenty.
The giant whitefly and the red imported fire ant are just that–imported. Known as exotic or invasive pests, they are nonnatives that originally came from other parts of the world–more than likely traveling on vegetation. Though scientists can’t be sure, there’s a good possibility they were brought in by a home gardener.
“We’re getting a large number of urban pests into the state and the country as a whole,” says Tim Paine, chair of the Entomology Department and professor of entomology at UC Riverside. “People are traveling a lot and moving a lot of plant material.”
Before you wage a campaign to wring the neck of the gardener who brought the giant whitefly in, stop and consider your own plant transportation practices. OK, so that cutting you stuck in your suitcase from Aunt Mabel’s begonia hasn’t seemed to cause any problems. But can you be sure?
“We understand that people’s motives are good when they transport plants to remind them of a vacation, or fruit to give to family and friends,” Paine says. “Many of those people think that their case is an isolated one, but it only takes one pest. If we have 30 million people doing it just once, you can see how we have a significant problem.”Many exotic, invasive pests are hitchhiking or being smuggled in, agrees John Kabashima, the environmental horticultural advisor for the University of California Cooperative Extension at the South Coast Research and Extension Center in Irvine.
“Unfortunately, even people who are aware that it is illegal to smuggle fruit or plant material that can harbor pests often don’t appreciate or understand the long-term fiscal, biological and health significance of their actions,” he says.
Not only are exotic pests such as the giant whitefly irritating, some, like the Africanized honeybee and the red imported fire ant, pose major health threats. And they have negative economic ramifications.
One example is the Formosan subterranean termite, which is established in La Mesa near San Diego. According to the Center for Exotic Pest Research at UC Riverside, treatment of a single home that has been infested can cost more than $5,000.
The well-publicized Mediterranean fruit fly, which has been found in California for 25 years,
has cost millions to control. Should it ever become established here, the Center for Exotic Pest Research estimates that it will cost the state $1.4 billion a year.
Other hard-to-measure effects of exotic pest damage include the disruption of ecosystems and the negative effect on Southern California’s outdoor lifestyle.
Modern Transport Speeds the Invasion
Exotic pests aren’t a new phenomenon, says urban entomologist Michael Rust, director of the Center for Exotic Pest Research.
“The Argentine ant was first reported in California at the turn of the century, and many of our cockroaches came from other countries years ago,” he says. “The problem has become accelerated in recent years, though, because of globalization of the economy and the rapid movement of people and goods. Many of the insects that would never have gotten over here on a long sea voyage 100 years ago, make it on a 12-hour airplane flight.”
Says entomology professor Paine: “According to the California Department of Food and Agriculture, for the past 10 years, there has been an average of a new insect pest being introduced or established every 60 days. Some of them don’t become significant pests, but others go on to cause terrible damage.”
How can a small insect wreak so much havoc? Exotic pests become invasive for a number of reasons. They are able to quickly get a foothold here because they lack natural predators and parasites that regulate their populations in their native habitats.
Exotic pests also find Southern California hospitable, with a mild Mediterranean climate and the smorgasbord of plant species in our yards.“The plant diversity you see in our urban landscapes rivals what you see in tropical rain forests–the average gardener will have hundreds of species in a small area,” Paine says. “Add to that the fact that most of our gardens are well irrigated.”
The red imported fire ant would never survive in Southern California if it weren’t for urbanization and frequent irrigation, Rust says, because it is not a desert ant.
Exotic pests also do well because they can, in some instances, destroy native species.
“Many invasive pests eliminate native species, which has a dramatic impact on our vegetation,” says Rust. “This causes our native plants to have problems with pollination, fertilization and movement of seed.”
There are no easy ways to control exotic pests. In years past, herbicides and pesticides were used in an attempt to eradicate new pests, but it’s since been found that eradication is impossible.
“After the Second World War, we thought chemicals were the solution to our insect problems, but we eventually discovered that the pests just returned, often in higher numbers and resistant to the pesticides,” Rust says. “The pesticides also killed off beneficial insects, which don’t come back as readily.”
Today, researchers have discovered that a two-pronged approach is the best way to deal with exotic pests: using pesticides as a last resort; and allowing the natural balance of pests to natural enemies to work.
“The idea with biological control is to reduce pest species to low levels like they are in their native environment,” Paine says. “You want to go out in the garden, turn over a hibiscus leaf and find very little, if no whitefly.”
Biological control is not a quick fix, but scientists feel it is the only viable long-term solution. And when it works, it works well.What Can You Do?
Although few gardeners are scientists capable of introducing natural predators, there are ways to prevent the spread of annoying pests.
* Resist the temptation to smuggle in fruit or plants, and don’t buy plants from businesses that are not licensed to sell plant material in California.
* Contact the Orange County agricultural commissioner’s office ([714] 447-7100) or the California Department of Food and Agriculture ([800] 491-1899) when you see a new type of pest or an abnormally high population of a pest.
* Plant varieties that do well here. Use resistant strains when available.
* Vary the types of vegetation in your yard.. Most pests don’t attack a wide range of plants.
* Keep plants healthy enough to fight off pests by properly watering, fertilizing and pruning them..
