A survey of mealybugs infesting South-Brazilian wine vineyards

ABSTRACTMealybugs (Hemiptera: Pseudococcidae) are important pests of the grapevine Vitis spp. and are responsible for direct and indirect damage to production. The main mealybug species present in wine grapevine (Vitis vinifera L.) in Southern Brazil were identified and their incidence evaluated. Bunch-samples (n = 50) from 131 vineyards located in the Serra Gaúcha Region (RS) of Brazil were analyzed at harvest, and the occurrence of mealybugs in the roots was evaluated at the time of eradication of plants for replanting. Mealybugs were reared in laboratory until adulthood for species determination. The species Dysmicoccus brevipes (Cockerell, 1983), Dysmicoccus sp., Planococcus citri (Risso, 1813), Pl. minor(Maskell, 1897), Pseudococcus viburni (Signoret, 1875) and Pseudococcus sp. were identified in bunches. Dysmicoccus sp., D. umbambae Granara de Willink, 2009, Pl. citri and Pseudococcus sp. were found in the roots. Pl. citri (31.4%) and Dysmicoccus sp. (22.7%) were the most common species found in wine grape bunches in the Serra Gaúcha Region.

Comportamento de prova do pulgão-verde Schizaphis graminum (Rond. ) (Hemiptera: aphididae) em plantas de trigo tratadas com silício e dimetoato / Greenbug Schizaphis graminum (Rond. ) (Hemiptera: aphididae) probing behavior in wheat plants treated with silicon and dimetoate

No presente trabalho objetivou-se avaliar o efeito do silício e do inseticida dimetoato no comportamento de prova do pulgão-verde Schizaphis graminum (Rond.) (Hemiptera: Aphididae) em plantas de trigo. Os tratamentos foram: 1) silício no solo, 2) silício no solo + foliar, 3) silício via foliar, 4) silício no solo + aplicação de inseticida, 5) silício no solo + foliar e aplicação de inseticida, 6) silício via foliar + aplicação de inseticida, 7) sem silício e aplicação de inseticida e 8) sem silício e sem aplicação de inseticida. Os dados foram comparados pela análise de variância multifatorial para cada um dos fatores separadamente. Os dados de porcentagem foram analisados pelo teste de quiquadrado. Não foi verificado interação do silício e dimetoato e, também, do efeito isolado do silício no comportamento de prova do pulgão. Entretanto, em plantas tratadas com dimetoato, uma maior porcentagem de insetos apresentaram fase xilemática e um menor número de pulgões alcançaram o floema. De maneira geral, a aplicação do dimetoato mudou o comportamento de prova do pulgão-verde.

The aim of this work was to evaluate the effect of silicon and the insecticide dimetoate in the probing behavior of the greenbug Schizaphis graminum (Rond.) (Hemiptera: Aphididae) in wheat plants. The treatments were: 1) silicon in soil, 2) silicon in the soil plus foliar spraying, 3) silicon foliar, 4) silicon soil plus insecticide, 5) silicon in soil plus foliar and insecticide, 6) foliar spraying of silicon and insecticide, 7) insecticide and 8) untreated. The data was compared by the multifactorial analysis of variance for each one of the factors separately. The percentage data was analyzed by the test of Chi-Square. It was not verified interaction of silicon and dimetoate and, also, of the isolated effect of silicon in the probing behavior of the greenbug. However, in plants treated with the dimetoate, a larger percentage of insects presented the xylem phase and lower number of aphids reached the phloem. In general, the application of dimetoate changed the probing behavior of the S. graminum.

Effect of silicon applied to wheat plants on the biology and probing behaviour of the greenbug Schizaphis graminum (Rond) (Hemiptera: Aphididae)

Foi avaliado o efeito do silício, aplicado em plantas de trigo (Triticum aestivum L.) sobre o pulgão-verde Schizaphis graminum (Rond.) (Hemiptera: Aphididae). Plantas de trigo foram tratadas com silício incorporado no solo e aplicado nas folhas. Foram avaliadas as durações dos períodos pré-reprodutivo, reprodutivo e pós-reprodutivo, como também a fecundidade e a longevidade do pulgão-verde. O comportamento alimentar foi investigado utilizando-se a técnica de Electrical Penetration Graphs (EPG-DC) e "honeydew clock". Plantas tratadas com silício mostraram efeito adverso sobre o desenvolvimento do pulgão. A penetração dos estiletes não foi afetada pelos tratamentos com silício. Contudo, os estiletes foram retirados mais freqüentemente das plantas tratadas com silício, o que reduziu o tempo de prova. O xilema e o floema foram igualmente alcançados em todos os tratamentos e os pulgões permanecerem alimentando-se no floema por períodos similares. Entretanto, a excreção de honeydew foi reduzida no tratamento com silício, indicando menor taxa de ingestão ou maior retenção de seiva no corpo do pulgão. Portanto, alterações químicas e indução de resistência estão provavelmente envolvidas na redução da performance do pulgão, sem, entretanto, alterar seu período de alimentação.

The effect of silicon-treated wheat plants (Triticum aestivum L.) on the greenbug, Schizaphis graminum (Rond.) (Hemiptera: Aphididae) was evaluated. Plants were treated with silicon incorporated to the soil and by foliar spraying. Aphid development was evaluated by observing the duration of the pre-reproductive, reproductive and post-reproductive periods, as well as fecundity and longevity. Probing behaviour was investigated by using the DC electrical penetration graphs (EPG) technique and a “honeydew clock”. Silica treated plants had a clear adverse effect on aphid development. Stylet penetration was not affected by treatments showing no physical barriers by the plant tissue. However, stylet was withdrawn more often on plants treated with silica, resulting in reduction of probing time. Sieve elements were reached equally by aphids in all treatments and the insects remained ingesting phloem sap for similar periods. However, honeydew excretion was highly reduced indicating lower sap ingestion rate or higher sap retention inside the body. Chemical changes and induced resistance are possibly related to the reduction of aphid performance.