Scientists from Wageningen UR Greenhouse Horticulture have discovered natural enemies of Tuta absoluta, the much-feared tomato leaf miner that does not occur in the Netherlands yet, during research in the Kinderdijk nature reserve in the Netherlands. Several of these natural enemies appear to offer new perspectives for biological control of tomato leaf miner.
Tuta absoluta, or the tomato leaf miner, has its origins in South America where it is a common pest in the cultivation of tomatoes and potatoes. Since 2007 the insect has become a serious problem for tomato growers in Spain and Morocco. Moreover, the affected area was recently extended to cover the entire Mediterranean region. Last year the Dutch Food and Consumer Product Safety Authority (nVWA, previously the Dutch Plant Protection Service or PD) announced that the tomato leaf miner had been detected in the Netherlands, mainly in packaging stations that import Southern European tomatoes.
Dutch tomato growers have recognised the tomato leaf miner as a serious threat and are concerned that the pest’s advance could put cultivation with minimal pesticide residues at risk. Because this type of growing provides a competitive advantage over Spanish and Moroccan breeders, the Dutch sector asked Wageningen UR Greenhouse Horticulture and the Dutch Product Board for Horticulture to check whether Tuta absoluta can be controlled by using natural enemies.
Bait
To find out whether the exotic tomato leaf miner has natural enemies in the Netherlands, Tuta absoluta was used as bait for the indigenous fauna. In order to do so, tomato plants carrying eggs were brought to Kinderdijk, a nature reserve with a wide variety of insects. Scientists from Wageningen UR Greenhouse Horticulture carried out direct observations of the activity of natural enemies. Before the caterpillars could pupate, the plants were taken back to the laboratory and placed in a cage to collect any possible parasites.
Plants with many caterpillars were shown to work as a magnet for a variety of predators. In addition to ‘opportunistic predators’, the scientists found a plant bug that attacks the larvae and thrives well on tomatoes. A surprising result was the immediate activity of parasitic wasps belonging to the family Eulophidae that probably originated from related moths. One of these wasps successfully parasitized and produced offspring. This parasitic wasp is being cultured for identification and further research. If it is shown to be suitable, the scientists will start looking for a related but harmless moth for the production of the parasitic wasps and will develop an effective method to introduce them into the crop.
Note for the editor
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Images:
1) An parasitic wasp that is about to lay its eggs on a caterpillar of the tomato leaf miner, which burrows into the leaves of tomato plants and consumes then from the inside out.
2) The Kinderdijk nature reserve houses natural enemies of the much-feared tomato leaf miner.