RESUMO
Heat transfer process in the soil active layer is important for the knowledge of its thermal properties linked with climate issues. The objective of this work was to analyze the energy flux in different soil profiles by estimating the apparent soil thermal diffusivity ($ATD$). The study was carried out in Keller Peninsula, located at King George Island in four different sites differing by soil characteristics, as well as vegetation coverage and landscape setting. The $ATD$ was estimated in function of the long-term hourly temperature records at different soil depths. In addition, we estimated the seasonal mean of the $ATD$ and the freezing $N$-factor. Results showed that $ATD$ values were smaller at shallow depths and increased with depth. The diffusivity values presented lower variability in colder conditions, especially at deeper soil layers. Water content was the main factor affecting soil thermal diffusivity at sites $1$ and $3$ (more than $70$ and $63\%$ of probability). At sites $3$ and $4$ lower $N$-factors were observed, suggesting higher snow pack and permafrost closer to the soil surface. Hence, positive $ATD$ appears in the summer due to thawing increases soil moisture, while negative $ATD$ appears during the freeze of the snow pack and precipitation.
Assuntos
Pergelissolo , Solo , Regiões Antárticas , Estações do Ano , TemperaturaRESUMO
Monitoring the susceptibility of a pest population to pesticides is essential for resistance management programs. The objective of this research was to evaluate the genetic variability in pesticide susceptibility in populations of Bemisia tabaci (Gennadius) collected from different Brazilian agricultural regions through the use of two different tests. Four whitefly populations, two from Goiás state (GO-1 and GO-2) e two from Bahia state (BA-1 and BA-2), were tested against a susceptible reference one (SusIAC). A residual contact bioassay was used to evaluate the pesticide susceptibility of each population by using diagnostic concentration bioassays and by estimating the baseline susceptibility data to each one of the tested insecticides, acetamiprid, imidacloprid, thiamethoxam, chlorpyrifos and endosulfan. Adult insects of unknown age and sex were tested. Evaluations were performed after 24h for endosulfan and 48 h for the other chemicals. Both procedures showed significant differences in the susceptibility to the pesticides among B. tabaci populations. However, the discrimination among B. tabaci populations was more evident with the use of diagnosis tests. The population GO-2 was significantly less susceptible to the tested pesticides than SusIAC, mainly to neonicotinoids. The most critical resistance situation of B. tabaci was detected to thiamethoxam, followed by imidacloprid.
Assuntos
Hemípteros/efeitos dos fármacos , Hemípteros/genética , Inseticidas/farmacologia , Animais , BrasilRESUMO
O monitoramento da suscetibilidade de pragas a praguicidas é essencial para programas de manejo da resistência. O objetivo deste trabalho foi verificar a variabilidade genética de populações de Bemisia tabaci (Gennadius), oriundas de diferentes áreas agrícolas, quanto a suscetibilidade a inseticidas no Brasil, por meio de dois testes diferentes. Quatro populações de mosca-branca foram testadas em relação a uma população suscetível de referência (SusIAC); duas oriundas de Goiás (GO-1 e GO-2) e outras duas da Bahia (BA-1 e BA-2). Uma técnica de bioensaio do tipo contato residual foi empregada para realização dos testes: 1) teste diagnóstico da resistência; e 2) teste para obtenção das linhas de suscetibilidade das populações. Os produtos utilizados foram acetamipride, imidaclopride, tiametoxam, clorpirifós e endosulfam. Utilizaram-se insetos adultos não separados por sexo e nem por idade nos testes. As avaliações foram realizadas em 24h, para o teste com endosulfam, e em 48h, para os demais produtos. Ambos os testes revelaram variabilidade genética quanto à suscetibilidade de mosca-branca aos inseticidas. No entanto, a discriminação entre as populações de B. tabaci foi mais evidente com o uso de testes diagnósticos. A população GO-2 foi significativamente menos suscetível aos produtos testados que a SusIAC, principalmente em relação aos neonicotinóides. A situação mais crítica de resistência de mosca-branca foi com tiametoxam, seguida pelo imidaclopride.
Monitoring the susceptibility of a pest population to pesticides is essential for resistance management programs. The objective of this research was to evaluate the genetic variability in pesticide susceptibility in populations of Bemisia tabaci (Gennadius) collected from different Brazilian agricultural regions through the use of two different tests. Four whitefly populations, two from Goiás state (GO-1 and GO-2) e two from Bahia state (BA-1 and BA-2), were tested against a susceptible reference one (SusIAC). A residual contact bioassay was used to evaluate the pesticide susceptibility of each population by using diagnostic concentration bioassays and by estimating the baseline susceptibility data to each one of the tested insecticides, acetamiprid, imidacloprid, thiamethoxam, chlorpyrifos and endosulfan. Adult insects of unknown age and sex were tested. Evaluations were performed after 24h for endosulfan and 48h for the other chemicals. Both procedures showed significant differences in the susceptibility to the pesticides among B. tabaci populations. However, the discrimination among B. tabaci populations was more evident with the use of diagnosis tests. The population GO-2 was significantly less susceptible to the tested pesticides than SusIAC, mainly to neonicotinoids. The most critical resistance situation of B. tabaci was detected to thiamethoxam, followed by imidacloprid.
Assuntos
Animais , Hemípteros/efeitos dos fármacos , Hemípteros/genética , Inseticidas/farmacologia , BrasilRESUMO
This report has the objective of registering, for the first time in Brazil, the predator Stethorus (Stethorus) minutalus Gordon & Chapin (Scymninae, Stethorini). Larvae and adults were observed feeding on eggs and nymphs of the whitefly Bemisia tabaci Gennadius biotype B (Hemiptera: Aleyrodidae), on cotton plants under greenhouse condition in Piracicaba, SP. Probably, this coccinelid is an introduced species in the Country.
Assuntos
Besouros/fisiologia , Gossypium/parasitologia , Hemípteros/parasitologia , Animais , BrasilRESUMO
Este comunicado tem o objetivo de registrar, pela primeira vez no Brasil, o predador Stethorus (Stethorus) minutalus Gordon & Chapin (Scymninae, Stethorini). Larvas e adultos de S. minutalus foram observados alimentando-se de ovos e ninfas de Bemisia tabaci Gennadius biótipo B em algodoeiro em condições de casa de vegetação em Piracicaba, SP. É provável que esse coccinelídeo seja uma espécie introduzida no país.
This report has the objective of registering, for the first time in Brazil, the predator Stethorus (Stethorus) minutalus Gordon & Chapin (Scymninae, Stethorini). Larvae and adults were observed feeding on eggs and nymphs of the whitefly Bemisia tabaci Gennadius biotype B (Hemiptera: Aleyrodidae), on cotton plants under greenhouse condition in Piracicaba, SP. Probably, this coccinelid is an introduced species in the Country.