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The Bug That Saved California

Updated: Mar 14, 2022

In the early 1870s, ambitious farmers were cultivating sweet Valencia oranges amid the bountiful sunshine of California. Soon these citrus groves would become the proving grounds for the new science of biological pest control, pitting a rare species of ladybugs against an invading horde of pests in a battle for the future of citrus agriculture in California - and the world.

Orange tree bearing its fruit

Commercial agriculture drove the largest economic expansion in California since the discovery of gold. And oranges, initially brought there by Spanish missionaries, had become California’s most valuable commodity.

By the mid 1880s, with the advent of railroad boxcars, fruit traveling east was now worth $20 million annually (around $600 million today). Nothing, it seemed, could stop what many were calling a second gold rush. Then a fuzzy white bug suddenly appeared, touching off an environmental crisis. How the cottony cushion scale, a virulent tree pest native to Australia, was unleashed upon the citrus trees of the world is a bit of a mystery, but entomologists identified it as the new species Icerya purchasi. Its tiny red larvae hitched a ride on anything that moved, even the wind, and ravaged the state's citrus groves.

Some 600,000 orange trees were growing in California, and the number that succumbed to Icerya is unknown, but it must have been high: In 1887, the state’s citrus export filled 2,000 boxcars, but only 400 the following year.

In 1886, the deepening crisis prompted Charles Valentine Riley, then 43 and chief of the U.S. Department of Agriculture’s Division of Entomology, to dispatch two federal entomologists to start pesticide experiments. However, they found that no combination of ingredients could both exterminate Icerya and leave the trees unharmed.

Riley mused publicly about discovering Icerya’s “natural enemies.” Biological control of agricultural pests wasn’t a new concept - as early as 1762, the French East India Company imported mynah birds from India to control locusts on the island of Mauritius - but it had never been tried on such a scale, or when the economic stakes were so high. Riley’s eventual success launched the field of applied entomology - using bugs to protect crops - and secured his legacy as its founder. Today, conscientious farmers use integrated pest management plans that blend biocontrol with the judicious use of pesticides.

So, Riley sent a man called Koebele to Australia, where local entomologist Fraser Crawford had recently discovered the only known enemy of Icerya: a parasitic fly, Cryptochaetum icerya.

He arrived in Sydney in September 1888. After a spell collecting Crypto flies, he spotted a different insect in October that would change everything: a species of ladybug, now known as Novius cardinalis, eating a large Icerya. Neither he, nor Crawford, nor Riley, whom Koebele informed of the discovery by letter, recognized the force of nature Koebele had found.

From October 1888 through January 1889, Koebele shipped 164 Novius ladybugs, stored in freezers so they’d survive the 30-day trans-Pacific crossings. On arrival, they exhibited an insatiable appetite for Icerya.

Koebele studied Novius closely. Male and females copulated for days, then the females laid countless eggs as both sexes went on a feeding frenzy among the Iceryae.

In mere weeks, they had restored every tree at the 'test' Wolfskill Farm to its pre-infestation health without any negative side effects. Citrus growers throughout Southern California came to Wolfskill with Icerya-infested branches to take ladybug colonies of their own back home, where the new miracle bugs performed similarly.

The following spring, Koebele and his Novius ladybugs were being hailed as heroes by an adoring public. The fruit growers’ association gave him a gold watch and his wife diamond earrings - small tokens for his spectacular accomplishment, which has since produced incalculable returns worldwide. Today scientists refer to the episode as the first instance of modern biocontrol and the introduction of the Novius ladybug to California remains the standard against which all biocontrol efforts are measured.



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