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Tomato ‘Ebola’ alert! Are your crops safe?

By GEORGE MBAKAYA | July 2nd 2016
Doris Awino a tamato farmer at West Kano, Kisumu County sorts her products at her farm after harvesting which she claimed most of them had lost their value due to heavy down pour currently rocking major parts of the county. The price of tomatoes has now gone up from Sh 2000 to 2800 per crate. PIC BY COLLINS ODUOR

As the outcry against the ravaging Tuta absoluta disease of tomato continues to resonate in West Africa (Nigeria), farmers locally need to take precaution to avoid losses due to this menace.

Tuta absoluta which is also known as Tomato Ebola, is a devastating pest of tomato. This pest is crossing borders and devastating tomato production in both protected and open fields.

The infestation of Tuta absoluta has also been reported on potato and common beans.

Tuta absoluta pest spreads quickly; it has a high reproductive potential and a life cycle that can take between 24 to 76 days, depending on the environmental conditions.

Their activity is concentrated in the early morning and dusk; during the rest of the day they remain hidden among the leaves.

Adult lifespan ranges between 10 and 15 days for females and six to seven days for males. The female lays the eggs mainly on the leaves, although they can also be found on stems and sepals.

Eggs are laid isolated, thus facilitating their distribution on the crop.

What is even worrying is that, Tuta absoluta is a very puzzling pest to control.

Effectiveness of chemical control is limited due to insect’s nature of damage as well as its rapid capability of development of insecticide resistant strains.

Once you apply the chemical for the first time, it might work but, by the next planting season the moths will regroup and because it is a three-pronged attack – larva, pupa and the moth itself – it can position itself in the cravats of the tomato that the insecticide spray may not reach.

Another issue is that “larva is found in the ground and it operates at night such that when you are spraying in the day it is already sleeping – it has gone away.

The use of biological factors are still largely under development and not ready to combat this pest effectively and in a cost effective way.

Sex pheromone trap can be used as an early detection tool.

Mass trapping and lure and kill application of pheromone has been found effective to control Tuta absoluta.

The damage

The larvae of Tuta absoluta mine the leaves producing large galleries and burrow into the fruit, causing a substantial loss of tomato production in protected and open fields. The damage can reach up to 100 per cent.

This pest damage occurs throughout the entire growing cycle of tomatoes and has a high reproduction capability as adult female can lay hundreds of eggs during her life time.

Good agricultural practices

In tomato, infestation is found on apical buds, leaves, and stems, flowers and fruits, on which the black frass is visible. On potato, mainly aerial parts are attacked.

Many approaches can be adopted to tackle this pest. First approach is to attack the insect itself at the reproduction stage from the egg to adult.

It’s not about attacking at the point of attack, but killing the egg before hatching, that is completely wiping it off from the farm.

Crop rotation

Entomologist report can be used to identify the species of the pest, because it’s possible that the species that can survive in Nyeri and Kirinyaga for example, might not survive in Rarieda because of the varied temperatures.

Good agricultural practices is the safest way to control Tuta.

Crop rotation, crop removal and selective removal and destruction of infested plants are just a few cultural practices.

The wild host plants should also be removed to prevent further buildup of a potential population.

The use of pheromone traps is a reliable method to detect presence of the pest. Pheromone trap gives early warning of infestation and also shows the density of the insect infestation.

Mass trapping helps to reduce population in greenhouses. The technique involves placing a higher number of traps in the crop field in various strategic positions to remove a sufficiently high proportion of male insects from the pest population. It should be used in combination with other control measures to achieve tolerable level of damage and reduce reliance on insecticides. Mass trapping is a potential option for open field production.

Lure and kill is another promising approach to control the male adults of Tuta absoluta with minimum amount of insecticide application. The technique reduces the mating incidence therefore reducing the number of viable eggs.

Based on sustained release matrix, the product can release the pheromone over a long period normally over 6-8 weeks while sustaining the activity of the contact insecticide throughout the same period.

The idea of providing chemicals to combat the pest is not the best, rather, a long-term approach should be deployed by studying the life cycle and involve all entomologists who will provide a plan to eradicate it totally. The immediate control is use of chemicals, which is not a sure bet.

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