Verticillium Wilt Strikes Aimogasta’s Old Olive Groves
Verticillium wilt, a soil fungus that kills olive trees from the roots up, has wiped out about 147 of the 870 or so hectares of olives around Aimogasta in Argentina’s La Rioja province, and it has reached the four-hundred-year-old tree that Riojans call the father of their olive growing. The provincial legislature has declared a plant health emergency for the olive sector. Here is what is happening, why there is no quick cure, and why small growers carry most of the risk.
What happened
The emergency law was passed by La Rioja’s legislature last month. According to the Catamarca daily El Esquiú, its author, the provincial deputy Nicolás Martínez, who grows olives himself, warned that the disease was spreading from Aimogasta toward the groves around the provincial capital and across the border into neighboring Catamarca. Óleo Revista, reporting on the situation this week, said the outbreak affects some 230 small traditional producers for whom the olive crop is practically their only income.
The fungus is attacking large, old trees, and among them is the Olivo Cuatricentenario in the Arauco district, the tree from which, according to local tradition, the region’s olive growing descends. The Arauco variety itself, prized for the size of its fruit, is described as one of the most susceptible.
| Aimogasta outbreak | As reported |
|---|---|
| Olive area around Aimogasta | About 870 hectares |
| Area devastated so far | About 147 hectares |
| Small producers affected | About 230 |
| Crop of a 50 to 70 year old tree | About 400 kilos of olives |
| Last reported olive price | 70 US cents a kilo |
Why there is no quick cure
Verticillium lives in the soil. It enters through the roots and blocks the tree’s water-conducting vessels, so shoots and then whole branches wilt and die. The leaves typically curl and stay on the dead branch rather than falling, and dried flowers or fruit can hang on for months. There is no spray that cures an infected tree. The standard advice, repeated in the Argentine reports, is prevention: plant only healthy nursery stock, do not overwater, and when a tree is infected, pull it out by the roots and leave the hole open for at least a year before replanting.
That advice is brutal for a smallholder. A mature tree of 50 to 70 years gives about 400 kilos of olives a year, and a replacement will need decades to match it; the local estimates range from 30 to 50 years. The large new plantations financed under Argentina’s tax deferral schemes have been hit too, but, as Martínez pointed out, their trees are young, their owners have money, and they can replant quickly. The families around Aimogasta cannot.
- Martínez believes the disease arrived with new plants brought into the area, a common route for Verticillium everywhere.
- The law revives La Rioja’s provincial plant health commission, which had not functioned for nine years.
- Growers were already asking for an agricultural emergency because of difficulties selling their crop, so the disease adds to an existing squeeze.
What it means
For the world market, a few hundred hectares in La Rioja make no difference. Argentina has been planting olives fast, and its exports have been rising, as we noted when they set a new record. But the Aimogasta outbreak is a warning about how the new and the old sit side by side. When thousands of young trees are moved into a region in a short time, a soil disease can travel with them and end up in the old family groves that have no margin to absorb the loss.
It is also a cultural loss. Old trees like the Olivo Cuatricentenario are the living record of where a region’s olives came from, much like the ancient trees Crete set out to count, as we reported in our note on the island’s olive census, or Montenegro’s Stara Maslina. Losing one is not like losing a field of young hedgerow trees.
The cheapest way to start an olive grove is with cheap plants, and the cheapest plants are the ones nobody has checked for disease. Verticillium moves around the world in nursery pots and on soil stuck to machinery. The growers who stay clean are the ones who pay for certified stock, ask where it was raised and refuse to plant into ground that grew cotton, potatoes or other hosts of the fungus. That caution rarely shows up in a business plan.