No abstract

No abstract

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 (λ) 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.

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.

Essential oils extracted from leaves and fruits of Schinus areira (Anacardiaceae) were tested for their repellent, toxic and feeding deterrent properties against Tribolium castaneum (Coleoptera: Tenebrionidae) larvae and adults. A topical application assay was employed for the contact toxicity study and filter paper impregnation for the fumigant assay. A treated diet was also used to evaluate the repellent activity and a flour disk bioassay for the feeding deterrent action and nutritional index alteration. The essential oil of the leaves contained mainly monoterpenoids, with α-phellandrene, 3-carene and camphene predominant, whereas that from the fruits contained mainly α-phellandrene, 3-carene and β-myrcene. The leaf essential oil showed repellent effects, whereas that from the fruit was an attractant. Both oils produced mortality against larvae in topical and fumigant bioassays, but fumigant toxicity was not found against adults. Moreover, both essential oils produced some alterations in nutritional index. These results show that the essential oils from S. areira could be applicable to the management of populations of Tribolium castaneum.

Triatoma patagonica Del Ponte (Hemiptera: Reduviidae), a vector of Chagas' disease, is widely distributed in Argentina and is found in sylvatic and peridomiciliary ecotopes, as well as occasionally in human dwellings after the chemical control of Triatoma infestans. Anti-cholinesteratic products can be applied in peridomiciliary areas and thus knowledge of cholinesterase activity during embryonic development in this species might contribute further information relevant to effective chemical control. Cholinesterase activity was characterized by reactions to eserine 10(-5) m, to increasing concentrations of substrate and to varying centrifugal speeds. Acetylcholinesterase activity was detected on day 4 and was significant from day 5. A reduction in cholinesterase activity towards acetylthiocholine (ATC) was observed on days 9 and 10 of development. Cholinesterase activity towards ATC and butyrylthiocholine (BTC) in homogenates of eggs was inhibited by eserine 10(-5) m. The shape of the curve indicating levels of inhibition at different concentrations of ATC was typical of acetylcholinesterase. Activity towards BTC did not appear to be inhibited by excess substrate, which parallels the behaviour of butyrylcholinesterases. Cholinesterase activity towards ATC was reduced in supernatant centrifuged at 15 000 g compared with supernatant centrifuged at 1100 g. The cholinesterase system that hydrolyzes mainly ATC seems to belong to the nervous system, as indicated by its behaviour towards the substrates assayed, its greater insolubility and the fact that it evolves parallel to the development of the nervous system. Knowledge of biochemical changes associated with the development and maturation of the nervous system during embryonic development would contribute to the better understanding of anti-cholinesteratic compounds with ovicidal action that might be used in control campaigns against vectors of Chagas' disease.

PALAVRAS-CHAVE -Blattella germanica, araguaraíba, repelênciaABSTRACT -Plant extracts have been used all over the world as an alternative method to control pests. In our study, essential oil extracted from leaves and fruits of Schinus molle var. areira (L.) (Anacardiaceae) was tested for repellent activity against adult males of Blattella germanica (L.), in a choice-test arena. Essential oil was extracted by hydrodistillation. Half of a circular white filter paper of 9 cm diameter was treated with the essential oils and the other half only with the solvents. Each extract was tested at 176, 70 and 35.38 µg/cm 2 . The activity of the extracts was compared to the standard treatment with N, N diethyl-m-toluamide (DEET). The essential oil from leaves did not show repellency to B. germanica. The repellency response to S. molle var. areira essential oil from fruits was significantly different from the control at all doses tested. The response of the cockroaches to essential oil from fruit differed significantly from DEET at 70 µg/cm 2 and 35.38 µg/cm 2 . Antennectomy of cockroaches resulted in a diminished response to the test compounds.KEY WORDS -German cockroach, Brazilian peppertree, repellency.

ABSTRACT. 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.