In a search for sustainable options of greenhouse whitefly Trialeurodes vaporariorum (Westwood) management, the toxic and/or repellent potential of water, ethanolic, and acetonic extracts of Ambrosia artemisiifolia L. (Asteraceae), Comocladia engleriana Loes (Anacardiaceae), Piper auritum Kunth (Piperaceae), Raphanus raphanistrum L. (Brassicaceae), and Taraxacum officinale F.H. Wigg. aggr.* (Asteraceae) were evaluated. Repellency was assessed by the cylinder method (olfactometer), while toxicity and oviposition inhibition were assessed by the leaf immersion method. Acetonic extracts did not cause any repellent or insecticidal effect. In contrast, 200 mg mL -1 water and ethanolic extracts of R. raphanistrum and ethanolic extract of A. artemisiifolia had the highest repellent activity (76%, 72%, and 69%, respectively) although their activity decreased gradually over time. Ethanolic extracts of P. auritum (66%) and R. raphanistrum (56%) at 200 mg mL -1 were highlighted as being toxic, while the most effective in inhibiting oviposition were water extracts of R. raphanistrum (76.1%) and P. auritum (72.0%) and ethanolic extract of P. auritum (69.5%); however, concentrations lower than 60 mg mL -1 caused oviposition stimulation. Our results suggest that water and ethanolic extracts of R. raphanistrum and P. auritum represent a useful tool in integrated whitefly management.

Diaphorina citri Kuwayama (Hemiptera: Liviidae) is an invasive species in America and is the main vector of the pathogen associated with Huanglongbing, a deadly disease of citrus plants in the world. The management of such a problem includes the intensive use of insecticides to reduce vector populations and risk of pathogen transmission. As an alternative to synthetic insecticides to control D. citri, the present study determined the chemical composition of diverse plant essential oils and assessed the toxicity and repellency of oil extracts against D. citri. Their chemical composition and abundance were determined by gas chromatography coupled to mass spectrometry. Adults and nymphs were exposed to leaf citrus discs treated by spraying or immersion with different oil extract concentrations. Repellency was assessed by exposing adults to treated leaves in experimental arenas and determining the number of insects remaining on the leaf after different time periods compared with the control. The main oil compounds in the tested plants were anethole, verbenone, 4-ethyl-4-methyl-1-hexene, 4-allylanisole, and trans-tagetone. Oils from Rosmarinus officinalis L. and Schinus molle L. caused no repellent or insecticide effects on D. citri. In contrast, oil extracts from the Foeniculum vulgare Mill. and Tagetes species were toxic and/or repellent for both adults and nymphs. There was a positive relationship between toxicity and concentration. Oil extracts from Tagetes lucida, T. coronopifolia, and T. terniflora were repellent (> 92%) at 40 mg mL-1 ; this was correlated with the concentration and decreased over time. Essential oils extracts from the Tagetes species could represent a potential defense that could be integrated into the management of D. citri.

La escaza información sobre los efectos del aceite esencial de Tagetes lucida contra nematodos y la riqueza de poblaciones nativas de esta especie vegetal en algunas áreas en el Estado de México resultan condiciones favorables para derivar insumos naturales inocuos de esta especie que posibiliten enfrentar problemas de agallamiento por N. aberrans en la producción de jitomate. El objetivo de este estudio fue evaluar en condiciones de invernadero la aplicación de aceite de T. lucida de una población natural de Ixtapan de la Sal, Estado de México en la formación de agallas por N. aberrans en plántulas de jitomate. El aceite esencial se extrajo por hidrodestilación a nivel piloto con rendimiento en peso seco de 0.4% (mL 100 g-1) y se analizó por CG/EM identificando los compuestos mayoritarios siguientes: acetato de geranilo (40.8%), β-ocimeno (15.1%), nerolidol (8.1%), β-cubebeno (5.1%) y cariofileno (5.2%). Plántulas de jitomate en maceta se inocularon con N. aberrans (10 mL kg-1 de sustrato) y se les dosificaron concentraciones de aceite desde 0.01 hasta 10 mg mL-1, como tratamientos preventivos y de control, en intervalos de aplicación de aceite de 1, 2 y 3 semanas. La inhibición del agallamiento de la raíz fue consistente en el tratamiento de control (TC) que en el preventivo. En TC, concentraciones de aceite de 0.35 y 1 mg mL-1 produjeron 63 a 80% de inhibición del agallamiento y se obtuvieron valores de CL50 de 0.06 mg mL-1 para los intervalos 1 y 2, y de 0.13 mg mL-1 para el intervalo 3.

No abstract

Seasonal abundance of the Asian Citrus Psyllid, Diaphorina citri Kuwayama, wasevaluated on citrus groves in the region of Cazones, Veracruz, Mexico. For the period from February 2010 to February 2012, biweekly records for adult specimens were made using yellow sticky cardboard traps, as well as the presence of eggs, nymphs, adults, and natural enemies on the flush shoots were also registered. Psyllid populations occurred throughout the period of study, detecting population peaks on February, March, April and July in the citrus plantations. Increases of psyllid infestations were positively related to the abundance of new shoot flushes, and these in turn, were related to the temperature and rainfall. Natural enemies were not a decisive factor in regulating liviid populations, while the abundance of shoot flushes produced by citrus treescould play an important role in integrated psyllid management.