How to control Tuta absoluta on tomatoes in Nigeria

In May 2016, Kaduna State declared a state of emergency after a small moth hit about 80% of its tomato farms. Farmers called it “tomato Ebola”, and the price of a basket of tomatoes jumped within weeks. The pest is Tuta absoluta, the tomato leaf miner, and it is still in every tomato-growing state. The good news: farmers who check early and combine a few simple methods can keep it under control.

What is Tuta absoluta?

It is a small grey-brown moth, about 6 mm long. The moth itself does little harm. The damage comes from its caterpillars, which tunnel inside leaves, stems and fruit.

It breeds very fast. One female can lay up to 260 eggs, and in hot weather the whole life cycle, from egg to moth, takes only about four to five weeks. Numbers can build up quickly within one season.

Where and when it strikes

• Dry-season irrigated tomato in the north (Kano, Kaduna, Katsina, Jigawa, Plateau, roughly October to April) usually suffers the worst attacks, because heat speeds up the pest's life cycle.
• Rain-fed tomato in the south and Middle Belt is attacked too, especially where tomato is grown back-to-back all year.
• Tomato is its main food, but it also feeds on garden egg, Irish potato, pepper and weeds of the same family, such as nightshade.

How to spot it early

Walk your field at least twice a week, starting in the nursery. Look for:

• Pale, see-through patches (“mines”) in the leaves. Hold a leaf up to the light: you may see a small green or cream caterpillar inside.
• Dark droppings inside the mines.
• Small holes in green or ripe fruit, often near the stalk, with rot inside.
• Eaten or dying shoot tips on young plants.

If you find mines on more than a few plants, act at once. Waiting one or two weeks can cost you most of the crop.

How to control it, step by step

No single method works on its own. Spraying alone fails, because Tuta absoluta can become resistant to an insecticide within one season. Use these steps together.

1. Start clean in the nursery

• Raise seedlings under insect-proof netting, so moths cannot lay eggs on them.
• Transplant only healthy seedlings. Throw away any with mines.
• Start with good seed. Varieties such as Roma, UC82 and Rio Grande are popular with Nigerian growers.

2. Break the cycle on the farm

• Rotate crops. After tomato, plant maize, sorghum, onion or a legume, not pepper, garden egg or potato.
• Clear old plants and weeds after harvest. Pull up the old crop and burn it or bury it deep.
• Do not leave damaged fruit in the field. Collect it in a bag, tie it, and leave it in the sun to kill the caterpillars.
• Where your community can agree, a break of about six weeks with no tomato in the area starves the pest.

3. Use pheromone traps

A pheromone trap uses a lure that smells like a female moth to catch the males. Hang traps at plant height from the day you transplant:

• 2 to 4 traps per hectare to see how many moths are about;
• 20 or more traps per hectare to catch large numbers and reduce mating.

Change the lure every 4 to 6 weeks, or as its pack says. A water trap (a basin of soapy water with the lure hung just above it) is cheap to make.

4. Spray correctly, and rotate

When traps catch many moths, or you see fresh mines on many plants, it is time to spray. Two rules matter most:

1. Rotate between insecticide groups. Do not use products from the same group for more than two sprays in a row, or for more than about 3 to 4 weeks.
2. Spray early, while the caterpillars are small, and cover the undersides of the leaves well. A good knapsack sprayer, such as a 16-litre pulse sprayer, makes this easier.

A simple rotation is group 28, then 6, then 14, then Bt, and back to the start. Always follow the rate and the waiting time before harvest on the label, and wear gloves, a face mask and long sleeves. Many farmers find that cheap pyrethroids such as lambda-cyhalothrin no longer control Tuta well, so do not rely on them.

5. Protect the natural enemies

Some small bugs and tiny wasps eat Tuta eggs and caterpillars. Broad-spectrum sprays kill them too. Choosing targeted products like those above, and spraying only when needed, keeps them working for you.

Weekly checklist

• Walk the field twice a week and check leaves against the light.
• Count the moths in your traps and write the number down.
• Remove and destroy mined leaves and damaged fruit.
• Spray only when catches or damage rise, and note which group you used.
• Switch to another group after two sprays.
• Keep weeds such as nightshade cleared around the farm.

When to get expert help

If damage keeps spreading after two rounds of rotation, or you are planning a large dry-season farm, talk to an agronomist before spending more on chemicals. Our technical support team can identify the problem from photos and suggest a spray plan, and a consultation can help you set up a new tomato farm right from the start.

Frequently asked questions

Can Tuta absoluta be wiped out completely?

No. It is now settled in Nigeria. The aim is to keep numbers low enough that your crop still pays.

Which insecticide is best for Tuta absoluta?

None stays best for long. Rotating chlorantraniliprole, emamectin benzoate, thiocyclam and Bt works better than repeating one favourite product.

Does it attack pepper too?

It can attack pepper and garden egg, but tomato is its main food. Do not grow these crops one after another on the same land.

How much of my crop can I lose?

Unprotected fields can lose most of the crop, as Kaduna farmers did in 2016. Early checking and trapping greatly reduce the losses.

Tuta absoluta is beatable when you plan ahead: a clean nursery, traps from day one and a rotation of the right insecticides. Not sure where to start? Send us a message, and we will be happy to help. For maize pests, read how to control fall armyworm.