- The Washington Times - Monday, December 18, 2006


A tale of nature’s revenge, stretching back more than two centuries and halfway around the world, has come full circle in a battle of cactus, moth and man.

At stake is the survival of a Mexican national symbol.

The dull-colored cactus moth that reached Mexican territory this summer threatens to devastate Mexico’s nopals — the prickly pear plant that graces the country’s flag and is deeply interwoven in its history, culture and diet.

The moth didn’t migrate here from its native South America; mankind carried it — to Australia, South Africa and the Caribbean. That makes it a cautionary tale about the dangers of transplanting species, even in the good cause of “biocontrol” — unleashing one animal or plant to fight another, rather than using pesticides.

“It’s not the moth that’s to blame, but rather people,” said Jose Sarukhan, head of Mexico’s National Council on Biodiversity, talking about the first sighting of Cactoblastis cactorium on Isla Mujeres, an island off Cancun, this summer.

“Imagine what would happen if this plague reaches here and devours all the nopals in a country that’s [their] center of origin,” he said.

Analysts say millions of acres of semiarid Mexican land could become total desert without its approximately 100 native species of nopals, about half the world’s total. Birds and reptiles that use them for nesting, protection or food also would suffer.

The country faces “extreme … incalculable damage” if the moth jumps the five-mile strait between Isla Mujeres and the mainland, said Jorge Hernandez, director of Mexico’s plant safety agency, which is hacking and burning affected cactuses on the island.

He said his agency has reduced the island infestation by about 98 percent, and may lick it within a couple of months, but he knows the victory may not survive the next strong wind that carries fresh moths to Mexico’s shores.

When an agriculture department worker checking moth traps on Isla Mujeres found the telltale signs of larvae and dying cactuses on Aug. 1, it was a chronicle of a disaster dating back to 1788, when the British imported red cochineal bugs to Australia to produce dye for their redcoat uniforms and break Spain’s monopoly on the colorant. They also brought nopal cactuses to feed the bugs.

The dye production fared poorly, but not the cactuses; by the late 1800s, they had spread, making millions of Australian acres unfit for farming.

Australians tried unsuccessfully to eradicate the cactus with poisons until, in 1926, they found an answer in the cactus moth, which in its natural state had never moved far beyond the plains of Argentina.

Within six years, the problem was virtually eliminated, and the Australians were so grateful that they raised a monument to the moth. “It was a resounding success, often referred to as the poster child for weed biological control,” said James Carpenter, an entomologist for the U.S. Department of Agriculture.

The insects were similarly used in South Africa and, in the 1950s, were imported by some Caribbean islands that had little use for their native cactus species.

Carried by winds or mankind, they moved westward through the Caribbean and now threaten U.S. nopals, though apparently not other cactuses such as organ pipe or saguaro.

Now both countries face what may be a never-ending battle. U.S. researchers are releasing sterile male moths to reduce the population, while in Mexico, hundreds of workers comb the mainland for windblown moths.

“This is something that will continue, with no end in sight,” Mr. Hernandez said. The battle will last “for all the years of our lives.”

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