Carolina Sánchez Chopa

Population Growth of Rhopalosiphum padi L. (Homoptera: Aphididae) on Different Cereal Crops from the Semiarid Pampas of Argentina under Laboratory Conditions

The bird cherry-oat aphid Rhopalosiphum padi L. (Homoptera: Aphididae) is one of the main pests in a number of crops in the semiarid Pampas of Argentina. In the present study, the effect of different host plants, including Triticum aestivum L., ?~Triticosecale Wittm., Hordeum vulgare L., Hordeum distichum L., Avena sativa L., and Secale cereale L. on biological parameters of R. padi L. was studied in the laboratory at 24 ?} 1 ??C, 65 ?} 10% RH and a 14:10 photoperiod. Longevity, intrinsic rate of natural increase (rm), net reproductive rate (R0), mean generation time (T), doubling time (DT), and finite rate of increase (?E) of the bird cherry-oat aphid on the different cereal crops were estimated. Differences in fertility life table parameters of R. padi among host plants were analyzed using pseudo-values, which were produced by Jackknife re-sampling. Results indicated that beer barley might be the most suitable food for R. padi due to greater adult longevity (20.88 d), higher fecundity (41 nymphs female-1), higher intrinsic rate of natural increase (0.309 females female-1 d-1), lower doubling time (2.24), and lower nymphal mortality (22.2%). Therefore, it can be concluded from the present study that R. padi prefers beer barley for fast and healthy development over other cereal crops.

Composition and biological activity of essential oils against Metopolophium dirhodum (Hemiptera: Aphididae) cereal crop pest.

BACKGROUND Natural pesticides based on plant essential oils may represent alternative crop protectants. This study analysed the chemical constituents and bioactivities of essential oils from Schinus areira L., Rosmarinus officinalis L. and Tagetes terniflora Kunth against winged and wingless adults of Metopolophium dirhodum (Walk.). RESULTS The major component of S. areira was α-phellandrene, that of R. officinalis was 1,8-cineole and that of T. terniflora was cis-ocimene. Rosemary essential oil was more effective than the others in immersion method tests. In contact toxicity, the rosemary oil was the most toxic to wingless adults and the S. areira leaf oil was the most toxic to winged adults. All the EOs produced some degrees of repellency in adults and effects on the reproduction and demographic parameters. CONCLUSION These results showed that the essential oils from S. areira, R. officinalis and T. terniflora could be used as an alternative in the management of M. dirhodum.

First record of sexual forms of Aphis craccivora Koch (Hemiptera: Aphididae) on Medicago sativa L. (Fabales: Fabaceae)

Sexual reproduction of Aphis craccivora Koch is recorded for the first time in Semiarid Pampas of Argentina. This type of reproduction was found on Medicago sativa L. A brief description and illustrations of eggs, oviparous females and winged males are given