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Assis F.A.,Federal University of Lavras | Moraes J.C.,Federal University of Lavras | Auad A.M.,Embrapa Dairy Cattle Research Station | Coelho M.,Federal University of Lavras
International Journal of Pest Management | Year: 2013

We investigated sunflower leaf palatability to Chlosyne lacinia saundersii Doubleday & Hewitson (Lepidoptera: Nymphalidae) in plants treated with silicon (Si) and subjected to mechanical injury. We also examined the effects of those treatments on plant development. The experimental study was carried out as a completely randomized design, consisting of the six treatments (10 replicates each): (1) control, (2) plants mechanically injured, (3) Si applied around the plant stem (Si drench), (4) Si drench + injured, (5) Si drench + foliar spray, and (6) Si drench + foliar spray + injured. Si drench + injured significantly reduced the percentage of caterpillar-injured leaves (CIL), leaf area consumed (LAC), and caterpillar weight (CW), leading to increased caterpillar mortality. The only intrinsic plant characteristic affected by the treatments was Si content (SiC), which was higher in plants treated with either Si drench + foliar spray or Si drench + foliar spray + injured. Negative correlations were observed between SiC and the variables CIL, LAC and CW, whereas positive correlations were observed between CIL and LAC, CIL and CW, and LAC and CW. The treatment strategy of Si combined with artificial mechanical injury affects leaf palatability and development of C. lacinia saundersii, conferring resistance to sunflower plants as a function of Si accumulation, although it did not increase crop vegetative variables. © 2013 Copyright Taylor and Francis Group, LLC.

Ferreira R.B.,Federal University of Lavras | Moraes J.C.,Federal University of Lavras | Auad A.M.,Embrapa Dairy Cattle Research Station | Fonseca M.G.,Embrapa Dairy Cattle Research Station
Journal of Pest Science | Year: 2013

This study evaluated the impact of different CO2 levels on the biological characteristics of Mahanarva spectabilis (Distant) and on the performance of forage grasses. The signal grasses Brachiaria decumbens Stapf (susceptible) and Brachiaria brizantha (A. Rich.) (resistant), the elephant grass Pennisetum purpureum (Schum.), including the Roxo de Botucatu cultivar (susceptible) and the Pioneiro cultivar (resistant) and the insects were kept in climate-controlled chambers with constant low (250 ppm) CO2 levels, constant high (500 ppm) CO2 levels, or fluctuating CO2 levels (mean, 368 ppm). Among these three CO2 treatments, no significant differences were found in the nymphal survival of M. spectabilis when the nymphs were fed on two signal grass species. On the other hand, under a constant low CO2 level (250 ppm), nymphal survival rates were significantly lower when the insects were kept in Roxo de Botucatu and Pioneiro cultivars. The mean adult longevity values for M. spectabilis were not significantly different among the three levels of CO2 evaluated. We observed that increased CO2 levels improved the performance of M. spectabilis and elephant grass cultivars in accumulating dry mass, which was not evident in signal grass. We further conclude that the levels of susceptibility and resistance of the forages tested will be maintained in future scenarios under which atmospheric CO2 levels are expected to increase. © 2012 Springer-Verlag.

Leite M.V.,Embrapa Dairy Cattle Research Station | Auad A.M.,Embrapa Dairy Cattle Research Station | Resende T.T.,Embrapa Dairy Cattle Research Station | Frias M.P.,Embrapa Dairy Cattle Research Station | And 2 more authors.
Experimental Agriculture | Year: 2014

The objective of this study was to determine whether salicylic acid, nitric oxide (NO) and/or feeding by nymphs of the spittlebug Mahanarva spectabilis affect the concentration of total phenolic compounds and the dry matter content of different genotypes of elephant grass (Pennisetum purpureum). Four genotypes of elephant grass with varying levels of resistance to insect attack were treated with 4 mL of salicylic acid (1%) or 2 mL of NO per plant in the presence and the absence of nymphs. We determined the concentration of total phenolic compounds and the percentage dry matter of shoots and roots in the plants. We found that salicylic acid, NO and attack by M. spectabilis did not change significantly the total phenolic compounds concentration in any of the genotypes of elephant grass tested. However, we observed variations in the concentration of phenolic compounds produced between the resistant and susceptible genotypes, both in the shoot, when subjected to salicylic acid or nymphs, and in the roots in the presence of nymphs. Furthermore, the inducers resulted in variation in the dry matter content of the shoots and roots for most of the genotypes tested. Therefore, we conclude that chemical inducers and feeding by M. spectabilis nymphs cannot be used to elicit a resistance response in elephant grass by stimulating the production of phenolic compounds. Copyright © Cambridge University Press 2013.

Auad A.M.,Embrapa Dairy Cattle Research Station | Santos J.C.,Embrapa Dairy Cattle Research Station | Fonseca M.G.,Embrapa Dairy Cattle Research Station
Florida Entomologist | Year: 2014

The effects of various temperatures on the development and survival of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) and Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) fed on Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae) were studied, and some biological aspects among these predators were compared. On average, 70 nymphs of R. padi were added to each experimental unit with predator larvae and maintained at 12, 16, 20, 24, 28, or 32 °C. The duration (days) and survival (%) were measured for each immature stage of the two predator species. The developmental durations of all H. axyridis larval instars, the total larval stage, the pupal stage and total preimaginal stage were very long at 16 °C but shortest at 24 °C for the first, second and third larval instars and at 28 C for the fourth larval instar, the total larval stage and the total pre-imaginal stage. Both at 24 °C and 28 °C, 92% of H. axyridis completed the larva to adult cycle, whereas survival was significantly reduced in the 16 to 20 °C range. At the highest temperature (32 °C), 70% of H. axyridis did not reach adulthood. In the case of C. externa, the durations of development of all larval instars and the total larval stage became progressively shorter as the temperature increased from 12 to 20 °C. At still higher temperatures the developmental duration this insect remained almost constant. The predator completed the larval stage at all temperatures from 12 to 32 °C. However, at 12 and 16 °C, mortality of the larvae was greater than 88%, and 100% of the pupae perished. Although the lower threshold temperatures estimated for both predator species were very similar, the development period from larva to adult of H. axyridis was only 59% as long as that of C. externa. By comparing certain biological parameters including durations of development and survival rates of the two predator species, it is suggested that H. axyridis has intrinsic advantages over C. externa; however, additional factors must be considered when choosing the species of predator for biological control of R. padi on grass pastures in Brazil. © Florida Entomologist 2014.

Fonseca M.G.,Embrapa Dairy Cattle Research Station | Silva S.E.B.,Federal University of Lavras | Auad A.M.,Embrapa Dairy Cattle Research Station | Paiva I.G.,Federal University of Lavras | Borges C.A.V.,Embrapa Dairy Cattle Research Station
Journal of Insect Behavior | Year: 2013

The mating behavior of Mahanarva spectabilis (Distant) was studied under laboratory conditions. Virgin adults were individually maintained in transparent cages for observation of the mating sequence. Mating behavior of 23 couples was monitored during the photophase portion of the day. Copulation was observed in 17 of the 23 pairs. The mating sequence includes male approaching the female, mounting of the female, and copulation. Of the 17 mating pairs, 70.6 % mated on the second day after emergence. Most of the copulations began between 8 and 9 h after the onset of photophase. The average duration of copulation was 268 ± 24.9 min, and most pairs mated once or twice during their lifetimes. The mating behavior of M. spectabilis is important to understand because it determines the age and ideal time for further behavioral testing, which is essential for determining the cues involved in the communication system of the species. © 2013 Springer Science+Business Media New York.

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