Tomatoes that are harvested this year will have less pesticide residue than ever. The Consell´s Agriculture Department from Ibiza, (Spain) in 2012, has decided to fight the Tuta absolute.Three years ago it wreaked havoc on tomatoes, regardless of the chemicals used in many zones of the island. The Nesidiocoris tenuis, a bug, is the key element for fighting this plague. Can Joan de Camp (Sant Carles) farm, owned by Joan Marí Guasch, president of Agroeivissa, has had the opportunity of seeing this bug in action. How the insect got there remains a mystery, but the results were formidable: it did not leave any trace of the tomato moth.
Joan Marí along with the J. M. L. R. cooperative´s tomatoes
Mari decided last year to plant 1,000 okra plants, an exotic legume that is an essential part of the South American and Eastern cuisine. It is produced in India and is used to thicken soups and ragus, besides being a soothing and protective balm for the gastrointestinal mucous; grilled it is used as a garnish for meats and fish. Due to low demand (it's cultivation came after a special request) and its lack of resistance to storage, it is required to harvest daily and not use pesticides.
Without chemicals since July
During that daily contact with the the crop, the details of which Mari noted in his field notebook, he observed that the pests that attacked the okra (the aphid, the Heliothis spp. and whiteflies) left without being sprayed with chemicals. "A plague appeared and soon after, it disappeared. You could tell there was a balance, a predator for these pests," recalls Mari.
Even without knowing that this balance was made by the Nesidiocoris tenuis, he decided in mid-July and at his own risk, to suspend the pesticide treatments on one of three fields dedicated to growing tomatoes. The level of Tuta remained high, but, curiously, damages decreased. Although he did not understand how that was happening without the use of chemicals, he decided to risk it more: since early August he eliminated the treatment for all his plantation. All or nothing.
Result: "Damages decreased dramatically and I had an super production, between 30% and 40% more tomatoes than in previous years, after removing the weekly pesticide treatment." Not only on tomatoes but also peppers, eggplant and
other products.
other products.
In September, the laboratories of the Department of Agriculture hoped to find an explanation in each test plant that was analyzed. They found up to 25 Nesidiocoris tenui specimens, an heteroptera predator of the tomato moth and other pests in their larval stage. If there are larvae, then it follows there is Nesidiocoris tenui. They seek their prey, kill it with their stylet and suck their essence. It loves the white fly in all its phases, but prefers its larvae and eggs. If there are no bugs available it sucks on the plant, but the damages are less.
The Nesidiocoris tenui is an old acquaintance of the Department of Agriculture: they tried it for years -in fact, it is marketed in boats of 500 individuals- but with poor results. Perhaps as Javier de Pablos, head of department thinks, it didn't show good results because they were still using the chemical treatment alongside it. After what happened on the Can Joan de Camp farm, they have come to the conclusion that pesticides also harmed Tuta´s natural predator. Hence, for this year they have
decided to try an all or nothing approach, like Joan Marí, on several farms.
How did it come to be?
It is believed that the okra plant acted as a reservoir for the proliferation of Nesidiocoris tenui and from that that crop it passed to the tomato one, where it ate the Tuta eggs. They do not know if it came by chance, if there were loose specimens of previous scheduled crops or if there was a deliberate release in 2011.
The important thing is that it worked. Statistics show it´s true: at Can Joan de Camp farm, damages to the fruit fell to 2% of the crop (without chemical treatment), while in the remainder of the island´s tomatoes (treated) damages ranged between 5% and 15%. In addition, there was a notable "increase in production quality" and with "an absolute absence of waste." That is, more and better.
Given these results, by 2012 the tracking and control Tuta campaign will be different: tests will be scheduled on crops to determine the influence of using a plant reservoir of useful insects (Nesidiocoris tenui) to remove pesticides.
Source: Diariodeibiza.es