Factors affecting thrips (Thysanoptera: Thripidae) population densities in watermelon crops
Keywords:
Citrullus lanatus, Frankliniella schultzei, plant stage, rainfallAbstract
Watermelon, Citrullus lanatus (Thunb.) Matsum. & Nakai (Cucurbitales: Cucurbitaceae), is one the 5 most-consumed fresh fruits in the world. The thrips Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae) is an important pest of watermelon crops in tropical regions. Among the principal factors that regulate pest populations in crops are phenological stage of the host plant, weather and climate, and natural enemies. Thus, knowledge of such factors may allow the prediction of the risk of pest damage to such crops. The objective of this study was to identify factors that drive F. schultzei population densities in watermelon crops. During 2014 and 2015, we evaluated the effect of abiotic (weather) and biotic (phenological stage of leaves, and occurrence of natural enemies) factors on F. schultzei population densities on watermelon commercial crops. Frankliniella schultzei densities were higher in dry periods with more intense winds. Insect pest density was higher on younger leaves of plants in the vegetative stage. Frankliniella schultzei preferred to attack younger leaves of the plant located at the apex of the branches. The results obtained in this work suggest that the population growth of F. schultzei in watermelon crops is higher in periods of low rainfall. The population densities of F. schultzei depend on the phenological stage of plants, weather, and populations of natural enemies. Farmers should seek to preserve the populations of Chrysoperla sp. (Neuroptera: Chrysopidae), which are an important natural enemy of F. schultzei.
Resumo
A melancia, Citrullus lanatus (Thunb.) Matsum. & Nakai (Cucurbitales: Cucurbitaceae), é uma das cinco frutas frescas mais consumidas do mundo. O tripes Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae) é uma das pragas mais importante da cultura em regiões tropicais. Entre os principais fatores que regulam as populações de pragas estão o estágio fenológico da planta hospedeira, elementos climáticos e populações de inimigos naturais. Assim, o conhecimento de tais fatores possibilitam o entendimento da bioecologia destes organismos e servem de base para o planejamento do uso de métodos de controle. O objetivo deste estudo foi determinar os fatores que regulam a intensidade de ataque de F. schultzei à cultura da melancia. Durante 2014 e 2015, avaliamos o efeito dos fatores abióticos (fatores climáticos) e bióticos (fase fenológica das folhas e ocorrência de inimigos naturais) nas densidades populacionais de F. schultzei em lavouras comerciais de melancia. A densidade de F. schultzei foi maior no período seco com ventos mais intensos. A densidade da praga foi maior em plantas no estágio vegetativo. Frankliniella schultzei prefere atacar as folhas mais jovens da planta localizadas no ápice dos ramos. Os resultados obtidos neste trabalho sugerem que o crescimento populacional de F. schultzei é maior em períodos de baixa precipitação e dependem do estágio fenológico das plantas, dos elementos climáticos e das populações de inimigos naturais. Os agricultores devem procurar preservar as populações de Chrysoperla sp. (Neuroptera: Chrysopidae), que são um importante inimigo natural de F. schultzei.
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