Plutella xylostella cause considerable harm to the production of broccoli, Chinese cabbage, cabbage and cauliflower. The control of P. xylostella is mainly performed using commercial insecticides, which have even led to the emergence of resistant populations. Two easily available natural products found in different plants essential oil, thymol and eugenol, stand up as possible novel agents to control this pest. In this work a series of alkylated and acylated derivatives of eugenol and thymol were synthesized and screened for antifeedant, larvicidal and ovicidal activities against P. xylostella. The results of biological activities assays suggest that the novel 1,1’-[1,8-octanediylbis(oxy)]-bis(4-allyl-2-methoxy-benzene) (5) was the most toxic in the larvicidal test. Compounds 1-butoxy-2-isopropyl-5-methyl-benzene (8) and hexanedioic acid 1,6-bis(2-isopropyl-5-methyl-phenyl)-ester (10) were the most toxic in the ovicidal assay. The compound 8 presented the most antifeedant activity. Most of the compounds obtained were more active than commercially available insecticidal deltamethrin and azadirachtin.

Essential oils from the leaves, stems, flowers and fruits of Melaleuca leucadendra growing in the state of Pernambuco, Brazil, were analyzed using gas chromatography-mass spectrometry (GC-MS). The effects of the oils and their major constituent were evaluated on the agricultural pests Tetranychus urticae and Plutella xylostella in different stages of development. The analysis revealed a M. leucadendra chemotype rich in (E)-nerolidol (81.78 ± 0.90 to 95.78 ± 1.20%). P. xylostella was more susceptible to the oils and major constituent than T. urticae. The fruit oil was 1.5-fold more toxic than the leaf oil to T. urticae eggs. (E)-Nerolidol was 5.5-fold and 4.5-fold more toxic to T. urticae adults than the leaf and fruit oils, respectively. Azamax® used as the positive control was more efficient than the oils and (E)-nerolidol against T. urticae. However, the oils and (E)-nerolidol were more toxic to P. xylostella than Azamax®.

Laboratory bioassays on fumigation, ovicidal and oviposition deterrence activity of the essential oil from Indigofera suffruticosa and its constituents [eugenol, (E)-asarone, dill apiole, (Z)-asarone, thymol, (E)-nerolidol and safrole] against Tetranychus urticae were carried out. Components of Indigofera leaf oil were characterized by gas chromatography (GC) ad mass spectrometry (GC-MS), which revealed the identification of 17 components, representing 97.7 ± 0.6% of the total oil, with a high percentage of phenylpropanoids (89.9 ± 0.5%), among which eugenol (45.6 ± 0.4%) and (E)-asarone (17.4 ± 0.2%) were major constituents. The ovicidal activity and oviposition deterrence tests revealed that the essential oil as well as its main compounds affected the oviposition and hatchability of mite eggs. Eugenol and thymol were the most potent compounds and were approximately 225-fold more potent than the oil. The acaricidal action exerted by sesquiterpenes and phenylpropanoids of the leaf oil is also discussed. The results suggest that the Indigofera oil and selected components associated with ovicidal activity and oviposition deterrence can serve as the basis for a promising agent that could be used in the formulation of a product for use against the T. urticae.