MANGO - Tropical Fruits - page 276

fl owers and small fruit are removed during the fi rst few years to allow the
plants to become larger. In the tropics, fl ower induction is not dependent on
a cool winter and is regulated by the time since the last fl ush matured after
the sprouting induced by the synchronized peripheral pruning. If this shoot
sprouts too soon, then the new fl ush will be vegetative; if the apex has rested
for a longer period, a reproductive apex will form. The length of the rest period
varies with variety.
The main aim of mango producers in the northern hemisphere is to
harvest in March to April when prices are highest. In Central America, normal
fl owering occurs in January/February and the harvest then coincides with
that of Mexico. Mexico, as the largest world exporter and main supplier to
the USA, makes it dii cult for other supplies to compete, and prices are low
because of oversupply. Other northern-hemisphere suppliers use orchard
management practices to induce earlier fl owering and harvest 1-3 months
earlier to coincide with the better market prices. This is possible as a major
portion of Mexican mango production occurs under subtropical conditions
in northern Mexico and they are unable to signifi cantly modify the fl owering
time. Similar procedures are followed in other parts of the world in order to
achieve better economic returns by harvesting before the bulk of production
arrives to the market. During 'El Niño' years, when winter temperatures are
higher, Peruvian and Ecuadorean mango production is af ected, though little
can be done to overcome the poor fl ower induction.
For these orchard management practices to work ef ectively to advance the
fl owering date, the following factors should be taken into account: (i) the plant
leaf N concentration should be between 1.1 and 1.3% at the time of induction;
higher concentrations result in vegetative shoots; (ii) the soil moisture
content should not be low, in order to achieve a better reproductive response;
this is dii cult to control in the tropics if the induction time occurs during
the rainy season; (iii) the age and maturity of shoots, with older shoots that
have been inactive after vegetative growth and maturation being more likely
to dif erentiate into a reproductive shoot. To limit vegetative growth an anti-
gibberellin compound such as paclobutrazol is used. Low soil nitrogen and
moisture also play a role in reducing the occurrence of early vegetative fl ush;
and (iv) the ef ectiveness of the application of fl owering stimulants, where the
dosage, the tree coverage, age and state of the leaves and the time the product
stays on the leaves infl uence the outcome (Huete and Arias, 2007).
Steps to induce fl owering
Stimulation of new shoots
The primary goal is to stimulate abundant vegetative shoot production. This
is achieved by: (i) synchronizing peripheral pruning after harvest, which will
result in a uniform synchronous production of new vegetative shoots at the