It only took a few years for him Cryptoblabes gniediella become the nightmare of many winegrowers.
Difficult to observe by trapping, female moths enter vines around veraison and lay between 105 and 230 eggs. The latter are much smaller than those of eudemis and hidden within the clusters. Growers may see nothing ten days before harvest and face significant damage on harvest day. This is what happened in 2018 or 2020. They are even more helpless as conventional insecticides have difficulty reaching the pest.
In the Aude, the Chamber of Agriculture’s wine advisors are pinning their hopes on biological control. This year, they successfully tested Bioline Agrosciences’ Tricholine Vitis trichogram strategy.
The company explains that these 0.8 mm micro-insects lay their eggs in those of the grape moth to reproduce. Once parasitized, the pest’s eggs do not spawn destructive caterpillars, but other trichograms that will leave to search for new Cryptoblabes eggs.
In Fleury d’Aude, Sandra Bennamane set up a first trial on a Dephy Ecophyto farm in Narbonnais on 3 hectares of Mourvèdre on the edge of a pond. “Crypto pressure has been so strong there for several years that sexual confusion and Spinosad are not enough in this organic conspiracy.”
The winemaker held one hectare of control. In the second, he hung 100 Tricholine Vitis diffusers, each containing 5,000 trichogrammes in various stages of development, on cage wires in less than 30 minutes. In the third, he placed directly on the ground in 15 minutes 100 rectangular boxes containing trichograms. The operation was repeated 3 times. 45 days, 30 days and 15 days before harvest.
“One day before harvest, the control plot contained 34 caterpillars per 100 clusters. In the Tricholine Vitis mode, we counted only 2, or 94% efficacy. We found slightly more in T-Protect mode, 6, or 82% efficiency”.
Assisted by Bioline engineer Sandra Bennamane and the winemaker counted 16% of damaged bunches in the control mode, 6% in the Tricholine Vitis mode and 14% in the T-Protect mode. “These latest numbers need to be put into perspective, because they don’t say how much the groups have changed.” horse the counselor. Sandra Bennamane hopes to repeat this trial in 2023 comparing the effectiveness of trichograms with that of Spinosad to see if the good results obtained in 2022 are confirmed.
In Corbières, in Syrah, his colleague from the 30,000 Mont Tauch group judged them better than conventional insecticides sprayed once or twice on Syrah head-on.
Trichogram has an effect of 50 gold of protection. “They are also effective against eudemis and can be applied at the end of the season, giving growers time to judge the year’s pressure, as opposed to stopping mating.” emphasizes Sandra Bennamane, aware that the price of a release, €75/hectare, does not make the operation accessible to everyone. “It’s interesting for wineries that appreciate their wine and want to achieve optimal polyphenolic maturity”.
Other disadvantages: sensitivity of microorganisms to insecticides and sulfur. Bioline recommends allowing 7 to 42 days between the last insecticide treatment and the first release. At 4 kg/ha, the last wet sulfur must date at least 14 days before the first release. For powdered sulphur, this period can be increased to 42 days.