Some insects are stronger than chemicals

Agricultural producers in Ibiza use insects to tackle 'Tuta absoluta' pest

Seven years ago, Ibizan agricultural producers were on the verge of not growing tomatoes again. A 'Tuta absoluta' pest destroyed whole plantations and the only remedy to fight it, which was not entirely effective, was to use very expensive and dangerous chemical products. Joan Marí Guasch, president of Agroeivissa, decided to risk it: "There came a time when it seemed that all I could do was to take my chances. I didn't agree with the action plan we were forced to implement, which entailed the use of chemical products. The phytosanitary impact was huge. I thought it was outrageous, and the beneficial effects were scarce, so I decided not to try."

"To my surprise, the problem became gradually less severe, until it disappeared. It turned out that there was an insect in Ibiza called 'Nesidiocoris tenuis', and once the treatments were no longer applied, that insect started to act as a predator of 'Tuta' larvae." It did so with such voracity that the tomato pest practically disappeared.

Marí tells that "I haven't used any chemicals for seven years. Professionals from Murcia and Almeria have come to study this case in order to imitate it with their crops." The insect is part of the endemic auxiliary fauna, like other bugs that the Consell and the cooperatives use to combat pests. "The autochthonous nesidiocoris start spreading in the crops as of July, unless the tomatoes are treated with chemical products." The first tomato plants, however, sprout much earlier, at the end of March. Growers then release thousands of nesidiocoris (purchased from companies) in the greenhouses, even though they are not yet 100% effective at the time, since "they are limited by their photoperiod," says Joan Argente, Tragsa technician. That means that "it needs both hours of light and an adequate temperature, which are not yet recorded in March or early April."

Argente explains that "in greenhouses, we are unable to get the insect to settle down correctly due to its photoperiod. It needs a higher temperature and more hours of light. It manages to survive, but it is yet unable to fully control the 'Tuta'; hence why we have considered introducing another useful bug that also has 'Tuta' in the menu: the 'Trichogramma achaere', a small wasp. We are planning to release the 'Trichogramma' in some greenhouses as a test this year."

The agricultural producers are happy with the nesidiocoris, because it has helped them get rid of a major problem. With this insect, they only lose an average of 3% to 5% of the harvest in the open ground, and about 7% of the greenhouse production as a result of the 'Tuta' bites. "These are very low levels, compared to the losses caused when the pest first appeared. Back then, entire plantations were destroyed and the average damage was estimated at over 50%. Tackling it entailed the implementation of a number of chemical treatments that caused the production costs to increase a lot." This resulted in the activity becoming unprofitable, so there were many producers who even considered getting rid of their tomato plants and never growing them again.

Producers have benefited from the elimination of chemical treatments in several ways. Not only has the impact on the environment been reduced, but they have seen their profitability improve and, furthermore, they now have more free time.

Source: Ibiza Daily

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