Different levels of shade on population of grasshoppers and its oviposition preference on heliconias

ABSTRACT: Grasshoppers of the families Acrididae and Romaleidae (Orthoptera) are among the insects that defoliate heliconias and have been gaining status as pests of commercial crops of these plants in Brazil. The objectives of the present study were to identify the grasshopper defoliating heliconias in the municipality of Santo Antônio de Pádua, RJ (Brazil), to evaluate the effect of different levels of shade on the population of this grasshopper and the production parameters of heliconias, and to determine if this grasshopper has an oviposition preference among the heliconias evaluated. The experiment was in a completely randomized block design, in subdivided plots (four levels of shade in the plot, 0%, 30%, 50% and 80%, and four species of Heliconia: H. psittacorum, H. stricta, H. wagneriana and H. psittacorum x H. spathocircinata ‘Golden Torch’ in the subplot), with four replications. The grasshopper was identified as Cornops frenatum frenatum (Acrididae). An increase in shade resulted in a decrease in the number of oviposition holes from the grasshopper and the number of lateral buds. Shade did not influence the number of C. f. frenatum nymphs and adults and the number of flower stems. H. wagneriana was the most preferred species for oviposition by C. f. frenatum. Results suggested using screens to shade heliconia plants can help control C. f. frenatum populations, however, the light requirements of the heliconias should be considered to guarantee productivity.

摘要：直翅目（Orthoptera）蝗科（Acrididae）与癞蝗科（Romaleidae）的蝗虫，是剥食蝎尾蕉（Heliconia）叶片的昆虫类群之一；在巴西，这类植物的商业栽培田中，其作为害虫的地位日益凸显。本研究旨在鉴定巴西里约热内卢州圣安东尼奥-迪帕杜阿市剥食蝎尾蕉的蝗虫物种，评估不同遮阴水平对该蝗虫种群及蝎尾蕉生产性状的影响，并明确该蝗虫在供试蝎尾蕉物种间的产卵偏好性。本实验采用完全随机区组裂区设计，主区设置4个遮阴水平（0%、30%、50%、80%），裂区设置蝎尾蕉属4个物种：H. psittacorum、H. stricta、H. wagneriana以及H. psittacorum × H. spathocircinata ‘Golden Torch’，共设4次重复。经鉴定，该蝗虫为Cornops frenatum frenatum（蝗科Acrididae）。研究结果显示，遮阴水平升高会显著降低蝗虫产卵孔数量与侧芽数量；但遮阴对C. f. frenatum的若虫、成虫数量及花茎数量无显著影响。其中，H. wagneriana是C. f. frenatum最偏好的产卵寄主物种。本研究表明，利用遮阴网对蝎尾蕉植株进行遮阴可辅助控制C. f. frenatum种群，但需兼顾蝎尾蕉的光照需求以保障其生产性能。