“Three weeks ago, when I reported myself to Bio Centre, there were only two of us who identified ourselves. And there, we find ourselves in more and more numbers. » A market gardener based in organic farming in Chabris, Clément Nivet faces a hitherto unknown undesirable person on his farm.
A mite, penthaleus major of its scientific name, which, for several years, has become established in France, “only with market gardeners, in greenhouse crops”indicates Clément Nivet, Monday December 30, 2024. He learned it the hard way, at the beginning of December. “I have a spinach greenhouse that has completely disappeared. The leaves have turned white, almost silver. In less than a week, the mites wiped out 600 m2. »
Mites come out of the ground
And the arachnid spread. “Afterwards, it went to a greenhouse with carrots that were just coming out of the ground. In five days, 500 m2 were destroyed. » Then it was the chard that was affected. To fight against this plague “which develops with a lot of humidity and in temperatures between 5°C and 20°C”there are no real methods.
Visible to the naked eye, mites measure approximately 1 millimeter.
© (Photo NR, Gaspard Mathé)
“My technical advisor suggested pulling out all the crops and burning everything. » Technique tested the week of January 6 to 11, 2025. “We made two passes through the burner. » Back in the greenhouse, “by scratching, we realize that there are plenty of them in the ground”. To bring them back up, he put spinach plants in a row. “In three or four days, we will re-air the burner. »
After two burns in this greenhouse, the market gardener placed rows of young spinach plants. Mites are already colonizing them.
© (Photo NR, Gaspard Mathé)
His visit with Antonin, an agricultural engineer in training, at the International Exhibition of Plant Production Techniques (Sival, in Angers), Wednesday January 15, did not reassure him. “The professionals we met agreed that there is no treatment that works. » These same interlocutors were, “for the first time”, asked several times on the subject. “That’s the sign it’s exploding.” The year was humid and mild, conducive to its development. »
And he discovered that the parasite even went as far as Norway, “where it attacks crops in the summer. So, even if we have -20°C, that would not be enough to eradicate it. » Enough to put a big question mark on the rest of the season. “For the moment, I refuse to go to the markets. I don't want to risk transmitting this parasite to other producers. » For this same argument, he refused grubbing aid offered to him by customers, “it is not impossible that we bring dust mites back to us”.
-“There, I have 8,000 m2 greenhouses. They are all infested. Mounting greenhouses nearby would only postpone the problem. » And the information gleaned from Sival does not “are not reassuring; even conventionally, market gardeners cannot get rid of them”.
So, with his team, Clément Nivet will do tests. “I ordered airtight boxes to try different treatments. » Integrated pest management, essential oils, mushrooms… “We will write everything down and try to establish a protocol. » He has no choice. “I have been here for twenty years. This is the first time I have had to do treatments. I didn't even use Bordeaux mixture. »
In the best case scenario, Clément Nivet hopes to return to the markets of Châteauroux (Place de la République, Saturday morning) and Amboise (Indre-et-Loire, Friday morning) in the spring. Provided we find a cure. “I received a box of seeds on Thursday, I am already checking with the supplier if he can recover part of the order. In the current state, I cannot sow. »
He finds himself without income: “My cash flow will not allow me to keep going, with my three employees and two apprentices. » And the income from his crops in the open field “represent barely 40% of my turnover. If I only do that, it's doomed to failure. » His first meetings with the banks were inconclusive. “In the worst case scenario, we could move towards filing for bankruptcy, while waiting to be able to relaunch the activity in six months or a year. »
A mite “present for almost ten years in the region”
“It is very polyphagous, it becomes a major problem in market gardening if it is not detected early enough. We have damage that can be truly spectacular. »
Édouard Meignen, market gardening advisor at the Bio Center agency, has been aware of the presence of penthaleus major in the Centre-Val de Loire region “for almost ten years”. Farms have been “living with it for years”. This winter 2024-2025, it identifies infestations “in Loiret, Indre-et-Loire, Loir-et-Cher, and Indre”.
However, even “on a national scale, information is incomplete. We don't know how they get to farms. It is a pest that is not well studied. And the solutions proposed are not extraordinary, he regrets. It's really a hard blow. From December to February, there are a lot of things launched in leafy and bunch vegetables (chard, spinach, carrots, radishes, etc.)” So many plants that penthaleus major delights in.
