Agriculture Reference
In-Depth Information
CHAPTER 19
ONION DISEASES
R.B. MAUDE
19.1 INTRODUCTION: WORLD ONIONS
Onions (
Allium cepa
) are grown worldwide as a vegetable for human consumption.
They are harvested as dry bulbs that are eaten raw or cooked. In certain countries
e.g. Mexico, they may be thinned when young for use in salads. Also, they are
grown at high densities as green (salad) onions and as small bulbs for pickling.
Shallots (
A. cepa
var.
ascalonicum
)
and multiplier or potato onion (
A. cepa
var.
aggregatum
) are small bulb strains of
Allium cepa
.
This chapter concentrates on dry bulb onions that are grown in temperate,
tropical and sub-tropical regions of the world (Currah and Proctor, 1990;
Rabinowitch and Brewster, 1990; Rabinowitch and Currah, 2002). Globally, 32
million tonnes were produced in 1994 (Anon., 1995; Jones, 1998). Production
increased by 63% to 52 million tonnes by 2002 (Anon., 2003; Table 19.1). More
than 65% of these crops were grown in Asia, with China (about 45%) and India
(some 20%) the major producers of bulb onions (Anon., 2003; Table 19.1). Indian
exports of bulb onions have accounted for 70% of its total foreign exchange
earnings in fresh vegetables (Gupta
et al.,
1991). There the crop has been grown on
0.29 million ha with an annual production of 3.14 million tonnes (Gupta
et al.,
1994). Currently, world bulb onion yields average 17 tonnes per hectare with the
more mechanised nations achieving higher yields (Anon., 2003; Table 19.1).
Table 19.1. Dry bulb onion statistics, from FAO Production Yearbook for 2002 (Anon., 2003)
Tonnes ha
-1
Location
Area harvested
(1,000 ha)
Yield
(1,000 tonnes)
World
2972
51914
17
Asia
2014
33453
17
Europe
420
7409
18
Africa
276
3917
14
South America
159
3281
21
* North America
98
3604
37
Australia
5
250
47
* includes Central America
491
