MANGO - Tropical Fruits - page 278

nitrogen concentration of the leaves should be less than 1.3%; (iii) soil
moisture should be low; (iv) application at night when cool and days are warm
or after a cold front; (v) rain should not occur for at least 6 h after spraying
to avoid the product being washed of ; (vi) the whole tree should be sprayed to
runof ; this can take 8-20 l/tree. A spreader sticker improves the ef ectiveness
of the sprays; (vii) the best time to apply is after 4 p.m.; and (viii) the variety
should be responsive. The Indochina-Philippine varieties respond readily to
stimulation, while Indian variety 'Haden' responds better than 'Kent' or 'Keitt',
and 'Tommy Atkins' is the least responsive. Advancing fl owering date should
be done in several small steps (Duarte, 2002) to avoid losing production. In
the fi rst year, fl owering is brought forward 20 or 30 days, with a similar step
in the following year, until the desired fl owering date is achieved. Following
application, fl owering will occur in about 3 weeks.
Nitrates or other products do not induce or change apex dif erentiation:
if it is a vegetative apex, a vegetative shoot will sprout; if it is a reproductive
structure, a fl ower panicle will emerge; nitrates induce the bud to start
growing. The factor that determines whether a shoot apex produces a fl ower
panicle or a vegetative shoot is the age of the shoot from the time it started
to grow after the synchronizing pruning. The older the shoot, the greater the
possibility that a fl ower panicle will emerge. Normally 'Haden' shoots can be
sprayed 4 months after synchronization pruning, while 'Tommy Atkins' needs
5 months for similar results. Davenport (1993) proposed the following model
for mango fl owering induction in the hot tropics:
With paclobutrazol application :
Harvest − pruning + 1 month, paclobutrazol + 3 months = 4 months to
induce 'Haden'
Harvest − pruning + 2 months, paclobutrazol + 3 months = 5 months to
induce 'Tommy Atkins'
Without paclobutrazol application :
Harvest − pruning + 5 months to induce 'Haden'
Harvest − pruning + 6 months to induce 'Tommy Atkins'
The paclobutrazol treatment reduces by 1 month the time that the shoot
needs to be in a non-active stage to fl ower after nitrate application in the
tropics. The result is explained by postulating that gibberellins are fl ower-
formation inhibitors. Paclobutrazol and uniconazole have not been labelled for
use on fruit crops in the USA, though they are not translocated into the fruit.
Fruit yields
Fruit yields vary with cultivar, climatic and edaphic conditions of the
production site, cultural practices and other factors, such as diseases and