Tuta absoluta: biological control that works, or an expensive illusion

The war against Tuta absoluta is won before the pest wakes up

Does biological control against Tuta absoluta actually make sense, or is it just an expensive promise? Since the South American moth arrived in the Mediterranean in 2006, it has turned homegrown tomatoes into a luxury. A grower on the coast summed it up bitterly: the pheromone traps would fill up with adults overnight, and yet he did not harvest a single tomato without a larva inside. He stopped planting them.

What works: the parasitoid that attacks the eggs

Trichogramma achaeae, sold as Trichocontrol, parasitizes the pest's eggs. The key, according to accumulated experience, is to release it with the first adult flights and repeat the releases. Waiting until you see the tunnels in the fruit is signing the death sentence: once the heat sets in, there is nothing left to do. Bacillus thuringiensis, at 1 gram per litre every 7-15 days, wipes out the caterpillars within 24 hours and requires no pre-harvest interval. A kilo costs around 30 euros and, at 15 grams per backpack sprayer, lasts the whole season. Neem oil, more expensive, hampers the adults, and diatomaceous earth, cheap, also kills other insects indiscriminately.

What doesn't work: pheromones, tobacco and sulphur

Pheromone traps catch adults, but they do not prevent egg-laying. Tobacco and basil, no noticeable effect. Sulphur, excellent against fungi, does not touch the moth. And watch out for sulphates: never apply them above 30 degrees, during flowering or near neem. Those who tried everything recommend removing the affected parts and burning them, never composting them.

Biological control exists and works, but it demands military discipline and acting in advance. For the impatient gardener, the most sensible alternative remains a sock full of sulphur. Yet another season, the moth laughs at those who trusted in spring.