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Hosts

Nutrient deficiencies can affect any plant host. This summary focuses on the affects of boron deficiency on papaya fruit.

Distribution

Bumpy fruit of papaya is associated with boron deficiency. It is known to occur in many of the papaya growing areas of the world.

Symptoms

Deformity begins early but symptoms appear to become more severe as the fruit gets older. The bumpy appearance is a result of localized areas of the fruit being affected by the deficiency and cease to increase in size. Adjacent unaffected tissue continues to increase and result in a misshapen, bumpy appearance. The earliest symptoms usually occur in the young, developing fruits where bleeding of latex and initial deformation becomes evident. Seeds in affected fruit are often aborted or poorly developed and vascular bundles are often darkened. Under severe deficiency situations, height growth of trees may be affected causing a slight rosette effect and an associated stunting.

Biology

Boron deficiency in Hawaii appears to be related to shallow, rocky soils and dry conditions. Trees with deformed fruits typically have boron levels in petioles (dry weight basis) of about 20 ppm and below. Normal boron levels in petioles are about 25 ppm and higher.

Epidemiology

Since this disease is due to a non-parasitic causal agent, a discussion of the spread of this disease is not necessary.

Management

CHEMICAL CONTROL

Foliar applications of 0.25% borax (Na2B4O7ù10H2O) and ground applications with 1-3 kg/ha elemental boron have been effective in raising petiole boron levels and the prevention of deficiency symptoms on fruits subsequently formed.

References

Nishina, M.S. 1991. Bumpy fruit of papaya as related to boron deficiency. Hawaii Inst. of Trop. Agric. and Human Resources, Commodity Fact Sheet PA-4(B), Univ. of Hawaii, 3 pp.

Wang, D.N., and Ko, W.H. 1975. Relationship between deformed fruit diseases of papaya and boron deficiency. Phytopathology 65:445-447.

JANUARY 1993

3A-BORON

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