Southland Crop Pest Identified as Distinct Species

A nutrient-sucking insect that has caused more than $548 million in crop damage really is a distinct species, not a strain of the sweet potato whitefly as initially believed, a study found.

Because the insect causes a disease in squash called squash silver-leaf, it should be named the silver-leaf whitefly, Thomas M. Perring and other entomologists at the University of California, Riverside, said in Friday’s issue of the journal Science.

The pest has been known by various names, including the sweet potato whitefly, the poinsettia whitefly, the poinsettia strain and type B.

Identification of the pest as a species different than the sweet potato whitefly doesn’t affect control methods, which aren’t very effective, university spokeswoman Kathy Barton said.

But it will make a difference in the long-term effort to find another insect or other biological methods of fighting the whitefly, she said Thursday.

Methods to control the sweet potato whitefly may be less successful against the silver-leaf whitefly, Perring said.

In 1991, the whitefly caused crop damage amounting to $250 million in Texas, $141 million in Florida, $120 million in California and $37 million in Arizona, the researchers said. Other hard-hit states included Alabama, Georgia, Louisiana, Mississippi and New Mexico.

The whitefly attacks melons, cotton, alfalfa, lettuce, broccoli, cauliflower, carrots, celery, asparagus, squash, tomatoes and many ornamental plants. It sucks nutrients out of plants and secretes a sticky material that promotes growth of fungi. It also makes tomatoes ripen unevenly.

Perring and his colleagues conducted experiments that showed the silver-leaf whitefly is genetically distinct and reproductively isolated from the cotton strain of the sweet potato whitefly. No eggs were fertilized when scientists tried to cross the two species. They also found the sweet potato and silver-leaf whiteflies wouldn’t copulate despite showing courtship behavior.

The two species had been thought to be the same based on similarities in their appearance, Perring said.

“An important next step will be determining where the silver-leaf whitefly may be native, because studies of its native ecology may provide clues to effective management,” Perring said.