Necremnus tutae (Hymenoptera, Eulophidae) is widespread and efficiently controls Tuta absoluta in tomato greenhouses in SE Spain.
Biological control of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) by spontaneously appearing parasitoids (Necremnus spp.) was studied during 52 tomato crop cycles carried out in 42 greenhouses in South-East Spain between April 2017 and May 2018.Necremnus tutae (Reuter) was found in all greenhouses, reaching a successful T. absoluta control in 36 crop cycles (69%). Several pesticides were found to negatively affect the activity of N. tutae, e. g. sulphur applied by dusting, which is a common practice in organic crops. Consequently, many treatments were found to be counter-productive, resulting in significant crop losses due to T. absoluta damage. Biological control by N. tutae reached high rates of parasitism (up to 73%) and mortality (via host-feeding, up to 92%), throughout spring and summer, most likely due to the high temperatures during this period. Since N. tutae cannot easily be mass reared, it is not available for augmentative releases. Two key strategies should be followed to promote the contribution of spontaneously present parasitoids. Firstly, the application of pesticides against other pests and diseases should be reduced to a minimum, with selected methods and products. Secondly, the greenhouse environment can be made more suitable for parasitic wasps by planting selected flowering plant species for the provision of nutritional food supplements, i. e. nectar. The optimisation of biological control of T. absoluta by N. tutae offers a free and sustainable way to significantly reduce crop damage and insecticide usage in tomato crops.