262 Handbook of herbs and spices
0.5 kg of N, P, K, Mg in the ratio of 6-6-6-3 given three to four times per year. If
chlorosis occurs, it can be corrected by added iron, zinc and manganese. Some
advisers recommend minor-element spraying four times during the year if the trees
are on limestone soils. Moderate irrigation is highly desirable during dry seasons.
Heavy rains during blooming season interfere with pollination and fruit production.
Interplanting of different strains is usually necessary to provide cross-pollination and
obtain the highest yields. Only light pruning is required.
14.8 Soils, water and nutrients...............................................................
Carambola is not too particular as to soil, but does well on sand, heavy clay or
limestone and will grow faster and bear more heavily in rich loam. It prefers a
moderately acid soil (pH 5.5–6.5) and is sensitive to water logging. The plant often
becomes chlorotic in alkaline soils. It needs good drainage and cannot stand flooding.
Carambola need moisture for best performance. This means regular watering during
the summer months and during dry spells.
In soils of low fertility young trees should receive light fertilizer applications
every 60 to 90 days until well established. Thereafter, they should receive one or two
applications a year in deep soils or three or more applications in shallow soils where
nutrients are lost by leaching. Application at the rate of 0.5 kg per year for every inch
of trunk diameter is suggested. Fertilizer mixtures containing 6–8% nitrogen, 2–4%
available phosphoric acid, 6–8% potash and 3–4% magnesium are satisfactory. In the
more fertile soils of California, this program can be reduced.
The tree is prone to chlorosis in deficient soils but responds to soil and foliar
application of chelated iron and other micronutrients. Growth and physiological
processes of carambola plants under soil flooding and root growth restriction (Ismail
and Noor, 1996a; 1996b) and physiological changes as influenced by water availability
(Ismail and Awang, 1992) have been studied.
14.9 Pests and diseases...........................................................................
The carambola is relatively pest free except for fruit flies. No diseases of sufficient
importance are known. The fruit is damaged by fruit fly, fruit moths and fruit spotting
bugs in those areas having these infestations. In fruit fly susceptible areas fruit can be
bagged for protection. In Malaya, fruit flies (especially Dacus dorsalis) are so
troublesome on carambolas that growers have to wrap the fruits on the tree with
paper. Experimental trapping, with methyl eugenol as an attractant, has reduced fruit
damage by 20%. In Florida, a small stinkbug causes superficial blemishes and a
black beetle attacks overripe fruits. Reniform nematodes may cause tree decline (De
et al., 2000). Cold storage quarantine treatment for Hawaiian carambola fruit infested
with Mediterranean fruit fly, melon fly, or oriental fruit fly (Armstrong
et al.,1995) Caribbean fruit fly (Gould and Sharp 1990) (Diptera: Tephritidae) eggs
and larvae have been suggested. Studies on gamma irradiation as a quarantine treatment
for carambolas infested with Caribbean fruit flies have been made by Gould and Von
(1991).
Ibrahim (1994) has studied the biology and natural control of the scale Drepanococcus