Pesticide-resistant whitefly threatens US crops

For the first time in the United States, a pesticide-resistant whitefly, which carries crop-devastating viruses, has been found outdoors, raising concerns among fruit and vegetable growers.

The Q-biotype whitefly turned up in April in south Florida’s Palm Beach County, where landscapers were spraying the flowers and shrubs regularly with insecticides. Its discovery outdoors comes more than a decade after it was first found in a US retail nursery in Arizona.

Since 2005, the whitefly has also been found in about two dozen US states, but only in greenhouses.

It is already considered a major invasive pest worldwide.

Now that the Q-biotype whitefly is outdoors in the United States, researchers say it poses a serious threat to crops such as tomatoes, beans, squash, cotton and melons.

Having whiteflies outdoors makes the problem “much more difficult to control,” and they may never be fully eradicated, said Dr Lance Osborne, a professor of entomology at the University of Florida.

“The resistance to pesticides — that is what really sets them apart,” he told a few dozen growers who attended a recent session to learn about the whitefly in Homestead, an agricultural area south of Miami.

“The best single treatment we have kills 90-91 per cent of them. That is as good as we can do without multiple applications.”

The insects can also spread more than 100 viral diseases that weaken the plants and can make fruits and vegetables inedible.

Since its discovery outdoors in Florida in April, they have been found in more than 40 locations across the state, including residences, wholesale nurseries and retail plant outlets, crawling on the leaves of hibiscus, eggplant, lantana, ficus hedges and porter weeds.

‘A serious risk’
Whiteflies can live on 600 different kinds of plants, 300 of which are grown in Florida, according to the state agriculture department.

“The reason we are worried about the Q is because it has such a huge host range and is resistant to pesticides,” explained Dr Osborne.

“They attack so many crops — there is always something in the ground these things will attack.”

While the Q-biotype whitefly has not done any major damage yet in Florida, its emergence has kept agriculture officials busy organising inspections, working on plans to control the bugs and imposing quarantines around positive finds as necessary, a spokesman said.

“With our climate, robust international trade and more than 100 million visitors a year, Florida is a hotbed for agricultural pests and diseases,” Florida agriculture commissioner Adam Putnam said in an email to AFP.

“The Q-biotype whitefly poses a serious risk to Florida’s US$120 billion (S$160 billion) agriculture industry and the more than two million jobs it supports.”

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