Kelly Izlar

Invasion Of The Tomato Leaf-Miner

Originally published by Scientific American.

Darth Vader. Lex Luther. Tuta Absoluta. Megatronus Prime.

Which of these is not like the other?

Tuta absoluta is the scientific name of a moth no bigger than your eyelash. But considering how dastardly the pest can be, it might belong with the other bad guys.

T. absoluta has a voracious appetite, and its favorite food is tomatoes. In fact, its alter ego name is “tomato leaf-miner,” because it literally mines through tomatoes, destroying the plant and leaving the fruit pockmarked and inedible.

Illustration by Steven White: sketchysteven.tumblr.com.

Illustration by Steven White: sketchysteven.tumblr.com.

A female leaf-miner will lay about 260 eggs in a lifetime, which is 30-40 days. The eggs stick to the underside of tomato leaves and stems. After hatching, the larvae will nosh on every part of the plant. When satiated, they drop to the ground, pupate, and start the whole process over again.

So what? Insects sometimes eat our vegetables, and it’s unfortunate, but you get over it, right? Maybe that’s true if you only occasionally fancy a slice of heirloom tomato topped with gourmet sea salt. But tomato is one of the most produced and consumed horticultural crops in the world. In West Africa alone, more than 500,000 farmers make their living by growing tomatoes.

T. absoluta has been known to reduce crop yields by 80-100% on tomato farms. It attacks at any stage from seedling to sandwich, targeting farms and processing plants alike.

Muni Muniappan, the director of the Virginia Tech-led Integrated Pest Management (IPM) Innovation Lab, has made the fight against this invasive pest his personal crusade. He’s traveled to three continents to conduct workshops and consult with growers and politicians about how best to combat this menace.

The IPM Innovation Lab, funded by the U.S. Agency for International Development, is a collaboration of scientists from all over the world who work to find sustainable solutions to agricultural problems in developing countries; and the tomato leaf-miner is a big problem.

Hailing from South America, this pest hitched a ride across the Atlantic in 2006, showing up first in Spain, and then spreading through most of Europe, the Middle East, and North Africa. In the past four years, it has crossed the Sahara desert into Senegal.

With great speed, the leaf-miner established itself on both sides of the continent, decimating crops in the highlands of Ethiopia and the equatorial plains of Uganda, Kenya, and most recently, Tanzania.

Illustration by Steven White: sketchysteven.tumblr.com.

Illustration by Steven White: sketchysteven.tumblr.com.

Muniappan and other researchers have spent the past few years warning about the impending onslaught, but many smallholder farmers have still been woefully unprepared for Tuta’s appetite.

They have been frantically spraying insecticides to stave off the assault, but the pest is developing resistance to popular chemicals in these areas, while populations of beneficial insects are being wiped out. The frequent applications are not so good for humans either.

“There’s no silver bullet for Tuta,” Muniappan says. “An invasion is irreversible; we can’t eradicate it. But we can control it, and we need to use every means at our disposal.”

Muniappan’s prescription is “integrated pest management” in a nutshell.

Instead of focusing on one method of pest management, IPM recommends a combination of common sense practices. If one doesn’t work, all is not lost.

And in the case of Tuta absoluta, there are a number of viable steps to combat the hungry moth that don’t involve lathering pesticide over the tomatoes like mayonnaise.

In the early stages of invasion, researchers suggest installing sex pheromone traps and using biological and plant-based insecticides. Once the pest has settled into a field, farmers are encouraged to remove and destroy damaged fruit and apply less toxic pesticides more infrequently.

But studies show that releasing biological control agents would be the best move. This means using T. absoluta’s own natural enemies against it. Predatory bugs are already being used to fight Tuta in many European countries, and surveys have shown that there are a number of local insects that could be effective against Tuta on the African fronts. These “bioagents” also come without the hefty economic and environmental price tag of high-toxicity pesticides.

The first and greatest hurdle is almost always a lack of information. Farmers don’t necessarily know what’s whittling away at their crops and or how to defend themselves against it.

“We must establish relationships with locals, share data, and collaborate,” Muniappan says. “It is crucial that we educate growers – they see things first, and they have the most to lose.”

Researchers who work with the IPM Innovation Lab and other like-minded programs are stationed throughout the continent, hosting workshops, symposia, and farmer schools to help tomato growers learn to identify the signs and behavior of Tuta absoluta.

In most superhero comics, readers can usually distinguish heroes from villains, and good will most likely prevail over evil. But in the real world, ends don’t always justify the means, and there is rarely an unambiguous victory.

Tuta absoluta isn’t evil – it’s an insect that reacts naturally to an evolving environment. Climate change, shifting weather systems, global population growth, trade patterns – all of these are uncontrolled variables with unsounded impacts.

But the means by which this insect is adapting makes life harder for people who already struggle to meet basic needs. The IPM Innovation Lab and many other scientific and humanitarian programs around the world seek to strike a balance – helping people without hurting the environment.

“We’re trying to get the technology to the people who need it the most,” Muniappan says. “We can reduce pesticide use, which makes the environment safer. We can improve health and increase food production. We can make a difference in the lives of poor people in developing countries.”