Aspectos bioecológicos e químicos de Pachycoris torridus (Scopoli, 1772) (Hemiptera: Scutelleridae) na herbivoria de Jatropha curcas (Linnaeus) (Euphorbiaceae)

Abstract

Pachycoris torridus (Scopoli, 1772) (Hemiptera: Scutelleridae) is the only representative of the Scutelleridae family of agricultural impact in Brazil. This bug is the main pest of Jatropha curcas (Linnaeus) (Euphorbiaceae), which produces raw material for the production of biodiesel. This study has as objective to evaluate bioecological and chemical aspects of P. torridus in herbivory of J. curcas. The experiments were performed using different methodologies, filed in literature, adapted to the particular insect pest, besides the development of new methodology that evaluated the attractiveness of J. curcas in different direction and distance. The research was developed in the Chemistry Laboratory of Natural Products of the Federal University of Alagoas (LPqRN/UFAL) and in Physiology Laboratory of the Agrarian Science Center (CECA/UFAL) and in the field (in the cities of Maceio and Rio Largo) during the period of May 2011 to January 2015. Younger seedlings were more susceptible to the attack even with smallest infestation, which the pest control must be done when there are signs of infestation in this stage. The sequence of behavioral categories which induced the sexual receptivity before intercourse was described in twelve steps. The intraspecific communication of P. torridus was brokered by emission of compound volatiles within a short distance, vibrational signals, sound and groping, driven by the male and recognized by the female. To make a difference between the patterns already known, the 30 new color patterns can be included in literature records, from number 28 to 57. Jatropha curcas releases kairomones long distances (200m) which isolatedly attracts P. torridus for hosting and herbivory. In the chemical evaluations, the compounds identified in the cuticle of P. torridus were: (E)-2-hexenal, (E)-4-(oxo)-2-hexenal, (E)-2-hexenyl acetate, (E)-2-octenal, undecane, dodecane, 1-tridecene, tridecane, (Z,Z)-2,7-Octadien-1-ol acetate, tetradecane and tetradecanal. Species adults P. torridus release content from metathoracic glands during courtship and copulation to attract the opposite sex, being able to empty their reservoir. That bug doesn’t secrete sexual pheromone and contents of their metathoracic glands submit double behavioral activity (alarm and attractiveness) at different concentrations. The rejection of the males to the females with new color patterns was caused by the presence of the chemical compound 1-Tridecene, as well as by increasing the concentration of the compound (E)-2-Octenal.