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Home / Crop

Icipe imports South American wasp to fight tomato pest

Icipe researchers release wasps to help fight Tuta Absoluta at a farm in Gatitika village, Kirinyaga. [Lydia Nyawira]
Kenyan researchers have introduced a wasp native to South America as part of a comprehensive plan to help tomato farmers address, one of the most destructive pests currently plaguing their crop, tomato leaf miner (Tuta Absoluta).
The International Centre of Insect Physiology and Ecology (Icipe) has introduced the parasitoid wasp “(Dolichogenidea gelechiidivoris) as part of an Integrated Pest Management (IPM) method to save the crop.
The wasp from Peru where the Tuta Absoluta pest originates has been christened the ‘natural enemy’ of the insect.
Icipe coordinator of the Tuta Absoluta control project Shepard Ndlela said it is the only answer to the destructive leaf miner, and the success of the strategy will rely on the farmers' knowledge to implement a set of control measures.
Ndlela said the method would encourage the adoption of economical methods that are friendly to both human beings and the environment.
“The purpose of the project is to implement, disseminate and promote a sustainable and eco-friendly approach for reduction of tomato losses,” he said.
According to Ndlela, the wasp controls the pest by laying eggs inside the caterpillars of the leafminer insect and as they morph to adults in a slowed egg development, they kill the pest.
“When released in large numbers, the wasps spread rapidly looking for infested plant material,” Dr Ndlela explained.
Icipe researchers release wasps to help fight Tuta Absoluta at a farm in Gatitika village, Kirinyaga. [Lydia Nyawira]

The researcher said the wasps are specifically designed to destroy the pest.

“Farmers should refrain from applying too much chemicals on the produce and employ natural methods like the natural enemies to keep the population of the pest at minimal levels,” he said.
This will in turn promote the production of clean fruits and tomatoes for consumption.
During the launch of the wasp in Kirinyaga County, farmers were also trained on the use of traps that focus on the annihilation of the male pests to reduce reproduction. A single female moth can lay up to 260 eggs during its 30- to 40-day lifetime.
Based on the research, the Tuta Absoluta attractants are yellow and emit the female scent that attracts the male moths.
Peterson Nderitu, a research officer with icipe, noted that the traps and lures can be used for monitoring purposes and mass trapping.
“This informs the farmer on the population levels of moths thus giving information on when to start controlling the pest,” he noted.
The spread of tomato leafminer begins from the first stages of growing tomatoes where seedlings are transplanted into the fields or greenhouses while heavily infested where farmers were urged to ensure they establish clean nurseries.
“This results in tomato plants being attacked when they are still young thereby dying before the fruiting stage,” noted Ndlela.
In an effort to subdue the ever-increasing population of the pest, most farmers have resorted to use of a broad spectrum of synthetic insecticides that have not been tested and recommended for use on fruits and vegetables.
Michael Njue, a tomato farmer representative said farmers have been following an unguided chemical programme that saw them spray their produce at every stage of their growth which has been cited as the root cause of the menace.
Further to their desperation, they started importing chemicals from neighbouring Tanzania and Uganda and all have proven ineffective.
In addition, Ndlela said it is imperative for seedlings to be raised in a pest free nursery to ensure that seedlings are healthy before transplanting.
“This can be achieved by using lures and general cleanliness in the nursery or field,” he said adding that use of pesticides should be the last resort after trying all natural methods.
Farmers were also asked to practice farm sanitization by burying infested plants after harvest one metre underground rather than throwing them in open fields or abandoning them in the farm.
He noted that when tomatoes are attacked by the pest, farmers usually select un-infested tomatoes and throw the infested ones away.
“This practice is unacceptable and discouraged because when plants are left undestroyed the maggots continue to develop into adult moths which will lay eggs and start another destructive generation,” said Dr Ndlela.
He added that burying them ensures that all maggots in the leaves and tomato fruits fail to develop further and die.

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