Antixenosis of the Triozid, Triozoida limbata (Hemiptera: Triozidae) to Some Cultivars of Psidium guajava (Myrtaceae) in the Field

In the guava crop, insecticides are frequently used throughout the yr in an attempt to protect new shoots from the attack of the key pest Triozoida limbata (Enderlein) (Hemiptera: Triozidae). Research is essential to investigate the resistance of cultivars for management of T. limbata populations in sustainable production systems. We evaluated the preference of T. limbata on guava cultivars in the field, and determined the longitudinal and transverse incidence of the triozid for plants of Psidium guajava L. (Myrtaceae). The evaluations were carried out in an orchard located in the Embrapa Agropecuária Oeste, Dourados, Mato Grosso do Sul, Brazil, with 8 cultivars of P. guajava, from May 2013 to Jul 2014. There were 96 plants in the area used; they were evaluated biweekly, quantifying the number of immatures and adults of the triozid using new leaves from the apex of the branches to the second pair of leaves fully expanded in 4 main branches (branches leaving the trunk) per plant. Simultaneously, to capture adults 96 plants were monitored with a yellow adhesive trap (10 × 15 cm) fixed at the height of the canopy, and the traps were changed every 15 d. The cultivars ‘Cascuda' and ‘Kumagai' were non-preferred for immatures of T. limbata, whereas ‘Paluma,' ‘Tailandesa,' ‘Novo Milênio,' and ‘Pedro Sato' cultivars were susceptible. There was a significant difference in the incidence of T. limbata adults between ‘Sassaoka' and ‘Paluma' cultivars. For the adults caught in adhesive traps, ‘Sassaoka,' ‘Kumagai,' and ‘Cascuda' cultivars were not preferred, compared to ‘Paluma' (susceptible). No difference occurred in the incidence of nymphs and adults of T. limbata between the positions of the branches, nor between plants or streets. The ‘Cascuda' and ‘Kumagai’ cultivars are promising for guava breeding programs, aiming at resistance to T. limbata attack. To sample for T. limbata in orchards, one can evaluate the leaves of any of the 4 main branches that leave the trunk.