ABSTRACT Mandarins commercialization at international market requires seedless fruit production in addition to its ideal organoleptic and visual quality. The objective of the work was to evaluate the efficiency of applications of gibberellic acid and of copper sulfate during anthesis in reducing the number of seeds and in the productive behavior of the 'Nadorcott' mandarin in the conditions of the southern Brazil. The experiment was performed in an orchard of 'Nadorcott' mandarin trees grafted on Poncirus trifoliata. Two applications were conducted at anthesis with different levels and combinations of gibberellic acid and copper sulfate. Also, net was used as one of the treatments to prevent pollination. Net treatment provided a high frequency of seedless fruits, with greater skin color, however with less production. Gibberellic acid applications increased linearly the frequency of seedless fruits and with a maximum of two seeds. Copper sulphate applications did not affect any evaluated characteristics. Sprays of gibberellic acid of 100 mg L-1 concentration reduce the number of seeds per fruit and increase parthenocarpy, without effect on fruit size and peel color.

Resumo: O objetivo deste trabalho foi avaliar o número de aplicações sucessivas de ácido giberélico (GA3), no período de outono-inverno, quanto a seu efeito na redução do florescimento, na primavera subsequente após períodos de baixa carga de frutos (ano “off”), em tangerineiras 'Montenegrina' (Citrus deliciosa). As aplicações sequenciais a 40 mg L-1 de GA3 foram testadas de uma a quatro vezes, com intervalos de 21 dias, com início no final de maio. O experimento foi realizado em delineamento de blocos ao acaso, com quatro tratamentos e controle, quatro repetições e uma planta por unidade experimental. Floração, brotação, tipos de brotos, frutificação e diâmetro dos frutos foram avaliados. A frutificação diminui exponencialmente com o aumento da intensidade de floração. O uso de GA3 em duas, três ou quatro aplicações sequenciais, de maio a junho, maio a julho e maio a agosto, reduz a intensidade de floração e brotação em plantas com produção alternada na primavera subsequente, o que aumenta os brotos mistos e reduz os brotos florais. O uso de quatro aplicações sequenciais de 40 mg L-1 de GA3 promove grande incremento na frequência de brotos campaneiros e favorece o aumento da fixação e do tamanho dos frutos.

Abstract: The objective of this work was to evaluate the number of successive applications of gibberellic acid (GA3), during the autumn-winter period, for its effect on the reduction of flowering, in the subsequent spring after periods of low fruit load (off-year), in 'Montenegrina' mandarin trees (Citrus deliciosa). Sequential applications at 40 mg L-1 GA3 were tested from one to four times, at 21-day intervals, beginning in the end of May. The experiment was carried out in a randomized complete block design, with four treatments and a control, four replicates, and one plant per experimental unit. Flowering, sprouting, types of shoots, fruit set, and fruit diameter were evaluated. The fruit set increases exponentially with the reduction of flowering intensity. The use of GA3 in two, three, or four sequential applications, from May to June, May to July, and from May to August, at 21-day intervals, reduces the intensity of flowering and sprouting of alternate bearing plants in the subsequent spring, increasing mixed shoots and reducing floral shoots. The use of four sequential applications of 40 mg L-1 GA3 promotes a great increase in the frequency of single flower terminal leafy shoots and favors the increase of fruit fixation and size.

Neste estudo foi avaliada a abundância e a sazonalidade de Tetranychus urticae Koch, 1836 em três cultivares de Gerbera jamesonii Adlam., em cultivo comercial no sul do Brasil. Para avaliação destes parâmetros foram realizadas amostragens de abril de 2011 a fevereiro de 2012. Os ácaros foram obtidos a partir de flores e folhas retiradas de cada uma das cultivares. No total foram contabilizados 10.640 ácaros e de acordo com os testes, a cultivar "Pink Snow" apresentou maior abundância significativa. A análise estatística não evidenciou diferença entre o número de ácaros presentes nas folhas e flores. Em todas as variedades o maior número de T. urticae foi registrado na primavera

In this study it was evaluated the abundance and seasonality of Tetranychus urticae Koch, 1836 in three varieties of Gerbera jamesonii Adlam. in a commercial cultivation at the south of Brazil. For the evaluation of these parameters samplings were accomplished from April 2011 to February 2012. The mites were obtained from flowers and leaves removed from each one of the studied varieties. A total of 10,640 mites were counted, and in agreement with the tests, there were a significant larger number of mites in the "Pink Snow" variety. The statistical analysis didn't evidence conclusive differences in the mite numbers between leaves and flowers. In all three varieties the largest number of T. urticae was registered in the spring