Acid Lime Trees Research Articles

Teores de carboidratos em limeiras ácidas 'Tahiti' tratadas com paclobutrazol

O paclobutrazol (PBZ) pode retardar o crescimento e induzir o florescimento de citros mediante a inibição da biossíntese de giberelinas. Além disso, outras características das plantas podem ser influenciadas pela aplicação do PBZ, como as concentrações e distribuição de carboidratos. O trabalho foi realizado com objetivo de estudar as possíveis relações entre concentrações e distribuição de carboidratos na planta e a aplicação do PBZ, em limeiras 'Tahiti' enxertadas sobre limoeiro 'Cravo' e cultivadas em vasos de cinco litros. O PBZ foi aplicado nas plantas conduzidas em câmara de crescimento, sob temperatura controlada (28º C dia/ 18º C noite) e fotoperíodo de 16 horas de luz, com fluxo de fótons fotossintético de aproximadamente 170 µmol m-2 s-1. A aplicação do PBZ causou reduções significativas dos teores foliares de carboidratos por ter induzido maior florescimento da limeira ácida 'Tahiti'. A aplicação do paclobutrazol resultou no acúmulo de reservas de carboidratos nas raízes.

Hemipteran Hopper Species Associated with Acid Lime Plants (Citrus aurantifolia L .) in the Sultanate of Oman: Candidate Vectors of Witches’-Broom Disease of Lime

Regular monitoring of hemipteran hopper species (including psyllids) associated with small-fruited acid lime trees (Citrus aurantifolia L.) was conducted for four years using motorized insect suction to determine the possible vectors of witches’- broom disease of lime (WBDL). The study was done in two phases: monitoring was done in Habra village, Wilayat Wadi AlMaawal (Batinah region) for one year from June 2000 to May 2001; then monitoring was done in Maharah village, Wilayat AlMusannah (Batinah region), for a period of three years from May 2001 to April 2004. Twelve species of cicadellid leafhoppers and one delpahacid planthopper species were collected, while no psyllids were found. Hishimonus phycitis (Distant) (Cicadellidae) was the most abundant hopper (78.4 % of collected individuals). Next in abundance were Toya sp. (Delphacidae), Circulifera haematiceps? and a deltocephalin leafhopper, respectively constituting 10.4, 3.8 and 2.4 % of the total catches of the four years. Nine other species made up 5% of the total collection: Exitianus nanus (Distant), Cicadulina sp. (either chinai (Ghauri) or storeyi (China)), Emposca distinguenda (Paoli), Amrasca biguttula (Ishihara), Deltocephalus (Recilia) pruthii (Metcalf), Neolimnus aegyptiacus (Mutsumura) and three undetermined species (one Deltocephalinae, one Typhlocybinae and one undeterminable to subfamily). Catches of H. phycitis were highest from November to March and lowest from May to September. There was a significant linear relationship between number of H. phycitis and maximum and mininmum temperature. Relative humidity was not significantly correlated to number of H. phycitis. In Maharah, young lime trees were free from WBDL but the disease incidence increased with age. H. phycitis is the best candidate vector of WBDL. The potential of Toya sp., Circulifera haematiceps? and an undetermined deltocephalin as candidate vectors is discussed. Finally, it is suggested that regular sprayings of acid lime trees with effective systemic insecticides during November to March each year can greatly reduce the vector population and can prevent or delay the spread of the disease to a great extent.

Measurements of net radiation absorbed by isolated acid lime trees (Citrus latifolia Tanaka)

SummaryBy using net radiometers mounted on a circular frame rotating around the canopy, measurements of total all-wave radiation absorbed by two ‘Tahiti’ acid lime trees were carried out in an orchard in Piracicaba, São Paulo State, Brazil. The rotating system around the canopy of a tree was formerly idealized and used in New Zealand, allowing integration of all-wave radiation and photosynthetically active radiation absorbed. In an experiment in December 1997, a first device using six net radiometers mounted on a light frame was used. A bigger device, more like the one used in New Zealand, in terms of the number of radiometers and the frame, with a different torque system, was used in another tree on some days from July to September 2000. The performance of both devices is discussed, including the possible error sources when using the first model (1997) and the problems of torque transmission on the second. Despite the lack of a test to check the performance of the device and the problems presented in the year 2000, the results confirm the possibility of providing reliable measurements of the net radiation absorbed by isolated trees. Relations of the net radiation per unit area of projected canopy on the ground were determined with integrated values over different time scales (from 15 min to 24 h). Unique relations between net radiation and incoming solar radiation were obtained for both trees over several time scales. These relations are applicable only to high leaf density conditions and canopy geometry similar to the used in this study.

Witches' Broom Disease of Small-Fruited Acid Lime Trees in Oman: First MLO Disease of Citrus

Witches' Broom Disease of Small-Fruited Acid Lime Trees in Oman: First MLO Disease of Citrus