LIBRO-CONGRESO-CITRUS

S07
program were to increase fruit set, control fruit thinning, increase fruit size at harvest, reduce fruit drop
during maturation, and to maintain on-tree fruit quality storage particularly of the peel. Four different
cultivars of clementine were tested: ‘SRA63’, ‘SRA85’, ‘SRA88’, and ‘SRA92’; as well as two rootstocks: sour
orange and ‘Carrizo’ citrange. In this paper, the effects of Triclopyr (3,5,6-trichloro-2-pyridyloxyactetic acid),
as an alternative to 2,4-D (dichlorophenoxyacetic acid), were evaluated for the control of the pre-harvest
natural drop. Triclopyr treatments were more effective to control fruit drop and to protect the peel of the
mature fruit when applied early on fruit of 18-22 mm of diameter (about the middle of July) with respect to
treatments made at peel colour break time. This treatment in middle July alone determined the increase in
fruit size and sometimes the total yield per tree. Lower yield was generally observed in trees grafted on sour
orange than on ‘Carrizo’ rootstock. Triclopyr showed a strong thinning effect when applied to fruit of 6-13 mm
of diameter, thus negatively affecting quantity and quality of the yield. On the contrary, Triclopyr treatments
at peel colour break time allowed normal colour development.
S07P08
Foliar application effect of the 3,5,6-TPA on Tarocco red orange yield and fruit size in “on years”
of eastern Sicily orchard
Tumminelli R., Marano G., Carta Cerella D., and Sinatra V.
Servizio Fitosanitario Regionale Siciliano (SFRSICILY), Quarantine and crop protection service, Italy.
riccardo.tumminelli@regione.sicilia.it
In the last four years (2009-2012), a method of reducing alternate bearing of red oranges (Citrus sinensis)
of eastern Sicily was investigated. In 2009 and 2011, 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6 TPA)
treatments were tested for their ability to increase yield of commercially valuable large size red orange fruit
(6 - 8 cm transverse diameter). Commercially bearing 15-year-old ‘Tarocco’ red orange scion on sour orange
rootstock (C. aurantium) was used in this research. 3,5,6 TPA (30 g a.i./ha) plus 0.7% of paraffinic narrow range
mineral oil were applied in 3000 L of water (pH 7.0) per ha with a low-profile air-blast sprayer to the foliage of
one individual tree per treatment with 4 replicate trees per treatment when fruit averaged 10 mm transverse
diameter. Four untreated trees served as the control. Averaged across the 4 years of the experiment, 3,5,6-
TPA treatments in 2009 and 2011, reduced total yield and increased yield of commercially valuable large size
fruit in the ‘on’ years 2010 and 2012, and increased total yield and decreased commercially valuable large size
fruit in the ‘off ‘ year 2011. Flower induction in 2012 was increased in treated trees in set fruit that will reach
maturity during the ‘off’ year 2013.
S07P09
Fruit thinning of ‘Okitsu’ satsuma mandarin
Rivadeneira M.F1 , Gómez C. 1 , and Silva-Muller W. 2
1Instituto Nacional de Tecnología Agropecuaria. Estación Experimental Agropecuaria Concordia (INTA EEA Concordia), Entre Ríos,
Argentina; and 2Ando Cia. frivadeneira@correo.inta.gov.ar
The plant growth regulator naphthalene acetic acid (NAA) is used as a fruit thinning agent before the
physiological drop stage of citrus fruit. Chemical and manual fruit thinning of ‘Okitsu’ satsuma mandarin
(Citrus unshui) was studied in an experiment carried out at Concordia, Entre Ríos, Argentina. In the spring of
2010 and 2011, fourteen-year-old mandarin trees grafted on Poncirus trifoliata rootstock were sprayed with
NAA (at 0, 100, 200 mg L -1 ) 40 days after full bloom (DAFB). Manual thinning was done at 80 DAFB. Treatments
were: control (0 NAA), manual thinning (MT), 100 mg L -1 NAA, 100 mg L -1 NAA with MT, 200 mg L -1 NAA and
200 mg L -1 NAA with MT. Fruit number, cross sectional shoot area, and fruit diameters were measured at 40,
70, 120 and 160 DAFB in two shoots per tree. Yield per tree was recorded at commercial harvest time in three
trees per treatment. Physiological fruit drop at 70 DAFB was 20-26% and with NAA fruit drop was 30-48%.
In the first year, there was no significant effect in yield per tree or diameter of fruit at harvest, although NAA
increased the number of fruits with larger diameters. Chemical thinning might be a useful tool to improve
commercial harvests in ‘Okitsu’ satsuma mandarin.
112 - VALENCIA CONFERENCE CENTER, 18th-23rd NOVEMBER 2012