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It has been determined the antifeedant activity of a mixture of limonoids 1,7-di-O-acetylhavanensin and 3,7-di-Oacetylhavanensin (F18), isolated from seeds of Trichilia havanensis Jacq. (Meliaceae), and the neo-clerodane diterpene scutecyprol A, isolated from Scutellaria valdiviana (Clos) Epling (Labiatae), on fifth instar larvae of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). Choice and no-choice feeding assays, nutritional tests, and post-treatment studies indicated that scutecyprol A acts as an insect feeding deterrent against S. exigua, whereas the antifeedant activity of F18 is likely associated with a toxic mode of action. In addition, it was tested the hypothesis that S. exigua larvae will try to metabolize the compounds that are toxic by the induction of their detoxication systems, whereas no such induction happens for those compounds that are deterrents. The mixture of limonoids F18 significantly increased glutathione S-transferases during the treatment and post-treatment periods, whereas esterases were inhibited during the treatment period. On the contrary, scutecyprol A did not have any significant effect on any of the enzymatic processes. Hence, the metabolic response of S. exigua larvae to the ingestion of the secondary metabolites tested depends on their mode of action.Additional key words: esterases, glutathione S-transferases, limonoids, neo-clerodane diterpenes, nutritional indexes, Scutellaria, Trichilia. ResumenActividad antialimentaria de terpenoides y efectos sobre las enzimas de destoxificación de la gardama, Spodoptera exigua (Hübner) Se ha determinado la actividad antialimentaria de una mezcla de limonoides 1,7-di-O-acetilhavanensina y 3,7-di-O-acetilhavanensina (F18), aislados a partir de semillas de Trichilia havanensis Jacq. (Meliaceae), y del diterpeno neo-clerodano scutecyprol A, procedente de Scutellaria valdiviana (Clos) Epling (Labiatae), frente a larvas de 5º estadío de la gardama, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). Los resultados de ensayos de preferencia y no preferencia, de ensayos nutricionales y del estudio de los efectos post-ingestivos indican que el scutecyprol A actúa como disuasorio de la alimentación frente a larvas de S. exigua, mientras que la actividad antialimentaria de F18 está asociada a un modo de acción tóxico. Además, se ha comprobado la hipótesis de que las larvas de S. exigua tratan de metabolizar los compuestos que son tóxicos mediante la inducción de enzimas de destoxificación, mientras que esta inducción no es necesaria para aquellos compuestos que son disuasorios de la alimentación. La mezcla de limonoides F18 incrementó de forma significativa la actividad glutatión S-transferasa durante los periodos de tratamiento y post-tratamiento, mientras que la actividad esterasa se redujo durante el periodo de tratamiento. Por el contrario, el scutecyprol A no tuvo ningún efecto significativo sobre estos procesos enzimáticos. Se puede concluir, pues, que la respuesta metabólica en larvas de S. exigua depende del...

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A field survey for insects associated with amaranth Amaranthus hypocondriacus L. (Amaranthaceae) was conducted in the semiarid Region Mixteca of Puebla State in Mexico. Also, the losses to the crop caused by the phytophagous species were assessed. Samples were collected every fifteen days during one year in five plots to obtain a representation of the phytophagous and beneficial insects, and of the percentages of plants infested with the principal phytophagous insects. The species that were observed causing considerable damage to the crop were Hypolixus truncatulus Fab. (Coleoptera: Curculionidae), Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), Pholisora catullus (Fab.) (Lepidoptera: Hesperiidae) and Phyllophaga ilhuicaminai Morón (Coleoptera: Melolonthidae). Borers infested 92% of the crop, while the white grubs group 45%. Yield losses by general insects without pest control program were 65.5%. Foliage and soil insects reduced the yield to 44.2 and 39.1%, respectively. This is the first report of quantification of losses due to pest insects in the amaranth crop.

Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae) is an important grapevine pest in Europe recently encountered in America. Trichogramma cacoeciae Marchal (Hymenoptera: Trichogrammatidae) is amongst the most effective parasitoids for Lepidopteran species. Studies to evaluate the effect of kaolin, an inert, nontoxic mineral, on oviposition, egg hatch, and neonate mortality of these species were carried out. Efficacy on L. botrana neonate larvae, oviposition, and egg hatch was evaluated. Effects of kaolin on parasitism and emergence of T. cacoeciae from L. botrana and Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) eggs were also evaluated. Lobesia botrana egg hatch and oviposition rates were reduced, and neonate larvae mortality was significantly greater in kaolin-treated arenas and when included in synthetic neonate larvae diet. Kaolin had no effect on T. cacoeciae parasitism in both hosts. There was only a slight but statistically insignificant effect on T. cacoeciae progeny emergence from L. botrana eggs and no effect from E. kuehniella. The results involving reductions in L. botrana oviposition and egg hatch and increase in larval mortality with kaolin suggest this compound may contribute to reduction in population densities and can be considered in rational integrated pest management strategies for L. botrana. Due to the laboratory results presented on parasitoid emergence, even though field bioassays would give a more exhaustive evaluation, it appears kaolin can be compatible with T. cacoeciae in L. botrana management.