A costly mistake

The first thing you look at is the center of origin of the crop," Bellotti explained. "That's classical thinking." Cassava's origin is in the American- it was taken from there by Portuguese traders to the Congo basin at the end of the sixteenth century—so there the hunt began, particularly in Central America and in northern South America. This was also the area of origin of the insect's genus. Then, in 1975, they thought they had found it. A taxonomat identified some mealybugs as the same insects as those eating the very heart out of Africa All they now had to do was find out which "natural enemies" were controlling it in the Americas and then send these "enemies" over to Africa. A type of beetle was suspected to be doing the trick, 50 they were soon Africa-bound. "But here's where it gets mysterious," Bellotti said. "The beetles didn't work."

A puzzled Hans Herren the project leader who at that time made his headquarters in Ibadan, Nigeria, arrived at El Centro Internacional de Agricultura Tropical (CIAT) in Cali, Colombia, from Africa to look at the colonies of mealybugs that Bellotti was rearing. Herren realized at once that these were a different species of mealybug. They had the wrong one-it had been a solution that was "simple, direct, and wrong."

I caught up with Hans Herren, an elegant and urbane Swiss entomologist, on a flight from Pans to the West African coast —he was resuming to his current laboratory in Cotonou, Benin and then again in Washington when he was attending an international conference. He had fought hard for the project for many years, and his professional colleagues in both Africa and Latin America were quick to praise his expertise and energy. "He was the driving force behind the project," one scientist told me. "He got in there at the beginning. He be" lived in it. Without him I don't think the thing would have gone."

The mealybugs they had in Colombia, Herren said, were males and females, whereas the mealybugs in Africa were only female. "And also the color was slightly different Ours were pinkish and theirs were greenish, which you couldn't see once the insects were killed and put in alcohol and sent to someone to identify" The African mealybug is called Phenacoccus manihoti. This new and different species had to be given a name" so it was named after Herren and became Phenacocuus herreni. Meanwhile the search for the "right" mealybug started all over again.

The Mind That Is Prepared

It was Tony Bellotti who eventually found it unexpectedly in a subtropical area much farther south than they had all thought—in Paraguay. In Africa the damage was in tropical areas, so looking in the Paraguayan subtropics was "not high on our list," he said.

He was on a routine trip to Brazil, Paraguay, and Peru in 1980, showing a new colleague around. After they had finished their business in Brazil and Paraguay, Bellotti decided to change his plans. He fumed to his companion and said:" there's really not much for me to do in Peru. I think I'm going to stay here in Paraguay an extra day or two. I want to go out and see some sites where we've got cassava."

About sixty kilometers from Asuncion, he walked into a cassava field and noticed that cabbage like effect on the leaves. It was typical mealybug damage. "I opened up the leaves and there were the mealybugs. I still didn't know whether we had the original species. So I collected them. Put them in a couple of vials. Brought then, back to Colombia and sent them off to the British Museum, to Douglas Williams, the taxonomist who was working on this. The interesting thing that happened next was that I came down with hepatitis. When you have hepatitis your mind sort of goes off. I was laid up and had forgotten about it Until I got a letter from Hans Herren saying: 'Congratulations you've found the mealybug. It's been identified as manihoti."'

Finding the mealybug was serendipitous, he admitted. "It was just by chance that I happened to be there, but the thing clicked. What was it," he asked, "that Louis Pasteur once said? 'In the fields of observation, chance favors only the mind that is prepared."'