Which Tomato Plant is Compatible with Which Natural Antagonist of the Tomato Leafminer?

Agroscope researchers tested three natural antagonists of the tomato leafminer on six tomato genotypes. Of the three genotypes displaying a degree of resistance, two were found to be compatible with the natural enemies of the pest.

The combination of host-plant resistance and biological control methods represents a promising strategy for the sustainable management of the tomato leafminer Phthorimaea (Tuta) absoluta, an invasive pest from Latin America that poses a threat to tomato crops worldwide. Combination trials of this sort are conducted because the tomato plants themselves can have a negative impact on the pest’s natural enemies, and can thus adversely affect the efficacy of the pest-control method used. In an Agroscope study, experts therefore investigated the performance of three natural enemies on six tomato genotypes with differing levels of reistance to the tomato leafminer P. absoluta.

Performance of natural antagonist only declined in one case

First, the effectiveness of the egg parasitoid Trichogramma achaeae was evaluated on the eggs of P. absoluta raised on various tomato genotypes. Next, the performance of the larval parasitoid Necremnus tutae was studied on tomatoes harbouring P. absoluta larva. Lastly, the predatory behaviour of the predatory bug Macrolophus pygmaeus towards P. absoluta eggs and larva was evaluated.

Neither tomatoes heavily infested with the pest nor the resistant domesticated tomato Corona F1 or the resistant wild tomato Solanum neorickii negatively affected parasitisation rates or the survival of the antagonist. By contrast, the resistant wild tomato S. arcanum reduced the performance of the two parasitoids and the efficacy of the predatory bugs.

Two tomato genotypes compatible with all of the natural antagonists

In summary, the study shows that the tomato genotypes Corona F1 and S. neorickii are compatible with all of the natural enemies, while S. arcanum is incompatible. One reason for these differences might be the dense glandular hairs in S. arcanum, which limit the mobility of the antagonists. In particular, the glandular hairs inhibit effective parasitisation by T. achaeae and N. tutae as well as the predation and survival of the predatory bug. Currently, it is unclear whether chemical constituents of the tomato plant have a toxic effect on the natural antagonists; further studies aim to discover whether this is the case.