Role of canopy height in the resistance of Lycopersicon hirsutum f. glabratum to Tuta absoluta (Lep., Gelechiidae)

The objective of this work was to study the effect of plant canopy height o n the resistance of the tomato species Lycopersicon hirsutum to the tomato leafminer Tuta absoluta. Determination of the levels of tridecan-2-one (2-T D) and undecan-2-one (2-UD) in L. hirsutum, as well as the leaf area, densi ty and types of trichomes present in L,. hirsutum and L, esculentum were ma de on apical, medium and basal parts of plant canopy. Correlation of these data were made with the following biological characteristics of T. absoluta : rates of oviposition and egg hatching; length of egg, larval and pupal st ages; mortality of the larval and pupal stages; pupal weight; and sex ratio . Levels of 2-TD on leaves of L. hirsutum increased from bottom to top of c anopy. Tuta absoluta had higher oviposition and egg hatching, as well as lo wer mortalities and smaller larval and pupal periods in L. esculentum than in L. hirsutum. Longer pupal period and greater number of small and large m ines of T, absoluta were verified in the apical and medium parts of L. hirs utum plants. On the other hand, higher pupal mortality and longer larval pe riods were obtained in the apical and basal parts of the L. hirsutum plants . Larval mortality was higher in the basal part of those plants. In L. escu lentum, leaves from the apical part of the plant promoted lower mortality, longer larval period and greater number of large mines of T. absoluta. Howe ver, a shorter pupal period was verified on leaves of the basal part. It ap pears that an increase in glandular trichome density in L. hirsutum leads t o an increase in the levels of 2-TD, which, in turn slows down larval devel opment.