INFLUENCE OF 2-TRIDECANONE-BASED RESISTANCE OF A WILD TOMATO ON PARASITOIDS AND PREDATORS OF THE TOMATO FRUITWORM, HELIOTHIS ZEA (BODDIE)

Heliothis spp. eggs were collected during 1984 to 1986 from field grown tomato lines varying in levels of glandular trichome-based resistance to Manduca sexta. Peak parasitism of eggs by Trichogramma spp. lagged 7 to 14 days behind peak oviposition of Heliothis hosts. Parasitism of eggs was greatest on the susceptible Lycopersicon esculentum cultivar, intermediate on the susceptible F{dollar}sb 1{dollar} (L. esculentum x PI 133417), and lowest on all variably resistant F{dollar}sb 1{dollar} backcrosses (F{dollar}sb 1{dollar} x PI 134417) and highly resistant PI 134417. Regression analyses indicated that trichome density accounted for the greatest proportion of variance of Trichogramma parasitism of eggs, and this negative relationship was best fit by the reverse logistic model.; No effect of 2-tridecanone-mediated resistance on parasitism of H. zea larvae was detected in field studies. However, parasitism levels were low and highly variable, averaging less than 11%. Second and third instar larvae were parasitized by Campoletis sonorensis, Cotesia marginiventris, and Microplitis croceipes. In cage studies, fewer H. zea larvae were parasitized by C. sonorensis on highly resistant plants than on susceptible or less resistant plants. Mortality of immature stages of C. sonorensis during cocoon construction was greatest on highly resistant and least on susceptible foliage. Removal of glandular trichomes by washing eliminated most C. sonorensis mortality on resistant foliage. Rearing H. zea host larvae on diet containing 2-tridecanone and 2-undecanone did not alter parasitism. Neither did host-mediated exposure of C. sonorensis to these allelochemicals precondition this parasitoid to higher mortality during cocoon spinning on foliage. LC{dollar}sb{lcub}50{rcub}{dollar} values of 2-tridecanone and 2-undecanone to cocoon spinning C. sonorensis larvae were 13.9 and 38.9 ug/cm{dollar}sp 2{dollar}, respectively. The direct effect of these chemicals, when combined, on last instar larvae was additive at low 2-tridecanone concentration and not different from 2-tridecanone alone at higher 2-tridecanone concentration.; In this study, the level of 2-tridecanone-mediated resistance did not alter the density of predators of Heliothis eggs and larvae on field tomato genotypes. Spider were the most abundant predators followed by Geocoris punctipes. We were unable to demonstrate a consistent plant genotype effect on abundances of small and large Heliothis larvae.