A team of Belgian researchers from various institutes recently reviewed their experience of biocontrol of tomato leaf miner during the Pure “IPM Innovation in Europe” conference held in Poznań, Poland in January. Since its first detection in Flanders (Belgium) in 2009, the South American tomato leafminer (Tuta absoluta) is now frequently encountered in tomato greenhouses in the region.
In the framework of the European Directive 2009/128/EC on the sustainable use of pesticides, an integrated control strategy against this pest in protected areas is being developed. It was assumed that the low temperatures commonly associated with Belgian winters would prevent the exotic species from successful overwintering. Experiments on cold-hardiness, however, demonstrated that the adults and pupae of this leafminer can overwinter in empty but frost-free greenhouses for at least two weeks. Therefore there should be aimed for an as low as possible population level of T. absoluta towards the end of the production cycle. This minimizes the number of overwintering adults and pupae, thus allowing the new crop to start in a clean environment which is the first step in an integrated pest management approach.
Currently Macrolophus pygmaeus is the most used commercial natural enemy against T. absoluta. Population build-up of this predatory bug is slow, making it difficult to control T. absoluta at the beginning of the production cycle or when pest levels are high. The population growth and distribution of M. pygmaeus in the greenhouse should be optimized by releasing the predator as soon as possible after planting in combination with the provision of food supplements. Laboratory experiments demonstrated that the predatory bug prefers the eggs of T. absoluta and preys only to a limited extent on the larvae. To complement the limited control potential of M. pygmaeus towards T. absoluta larvae, the efficacy of three commercially available entomopathogenic nematodes (EPN) Steinernema carpocapsae, S. feltiae and Heterorhabditis bacteriophora was tested against the four larval stages of T. absoluta. Control of the larger larval instars L3 and L4 was most successful, resulting in 71.8–97.4% mortality. The efficacy of the selected EPN was tested at 18°C and 25°C. At both temperatures, S. feltiae was most effective, killing 100% of the larvae after three days. The above findings show that EPN might be implemented in an IPM strategy to control this pest but appropriate spray application techniques need to be developed to obtain an optimal deposition of EPN infective juveniles on tomato leaves.