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.

Estimation of soil erosion using USLE and GIS in the locality of Tzicatlacoyan, Puebla, México | Erika María López-García, Edgardo Torres-Trejo, Lucia López-Reyes, Ángel David Flores-Domínguez, Ricardo Darío Peña-Moreno, Jesús Francisco López-Olguín | Agricultural Journals

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.

The chitinase enzyme was identified in isolated bacteria of maize rhizosphere as well as its potential for the biological control of fungi associated at seeds of the same plant. The production of chitinase enzyme was found in the genera identified as Acinetobacter, Bacterium, Burkholderia, Paenibacillus, Pseudomonas, Rhizobium, Shewanella, Sphingomonas and Stenotrophomonas. Bacterial isolates with ability to degrade fungal mycelium from maize fungi as Fusarium and Alternaria among others, were detected. Bacterial chitinase activity and the presence of the chiA gene were determined. The inoculation of chitinolytic bacteria showed a positive effect in the control of fungi in maize seeds. The results support the potential use of chitinase enzyme producing bacteria on the control of phytopathogenic fungi.