Water deficit, a common constraint in forestry, is the main cause of plant stress during plantation. The survival and growth of seedlings is also compromised by herbivory during establishment. The potential of nursery preconditioning to enhance survival chances of future trees by reducing palatability or attracting beneficial insects as a result of changes in chemical defences may be an answer to overcome this situation. Changes in essential oil production and composition were evaluated by GC and GC-MS in Eucalytus camaldulensis seedlings submitted to drought during four weeks at the last stage of nursery period (20 weeks). Significant changes in essential oil relative composition were found. Seedlings (young leaves) submitted to drought developed a terpenoid blend, which has been previously associated to mature leaves and related to their higher resistance towards herbivory. Total amount of non-oxygenated terpenes decreased by 44%, whereas some oxygenated sesquiterpenes (globulol, epiglobulol and ledol) were doubled, and 1,8-cineole content was enhanced by 28.3%.

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Aphids and thrips are very important pest species of many greenhouse and field plants in the world. In recent years, there have been attempts to identify plants for their insecticidal property with a view to find out suitable alternatives to the indiscriminate use of chemical pesticides, which are a risk for human health and the environment. The aim of this work was to evaluate the insecticidal effect of Eucalyptus globulus Labill essential oil (EO) against Aphis nerii Boyer de Fonscolombe (Hemiptera: Aphididae) and Gynaikothrips ficorum Marchal (Thysanoptera: Ploeothridae). The EO was extracted by hydrodistillation and the bioassay was evaluated by toxicity contact method, using solutions at different concentrations and for different time intervals. The EO was more toxic to G. ficorum (LC 50 = 0.031µL cm-2) than A. nerii (LC 50 = 0.099µL cm-2) on filter discs at 12 h of exposure. These results suggested that EO from E. globulus constitute a good alternative for the control of A. nerii and G. ficorum, considering their insecticidal effects at low applied concentrations and for short periods of time.

Chenopodium album L. plants grown in continuously cultivated and in nondisturbed soils were compared in terms of the compositions of nonpolar extracts of the corresponding aerial parts. Both light petroleum ether extracts of C. album L. were analyzed by high-performance thin-layer LC, capillary GC, and capillary GC-EI-MS. Further percolation and medium-pressure LC, along with EI-MS analysis, permitted the separation and identification of the chemical constituents. Differences were observed between mean contents of the chemical constituents of C. album L., with respect to nonpolar extracts, obtained from continuously cultivated and from nondisturbed soils, in particular in linear and branched long-chain hydrocarbons, FA and their esters, and long-chain linear alcohols and aldehydes. The most remarkable features of the disturbed soils were a pronounced increase in the amounts of linear hydrocarbons and a decrease in the relative proportions of FA.