CONTENTS

Introduction

Order of deficiency symptom appearance*	Deficiencies	Toxicities
1/ Disorders Producing Symptoms Mainly On The Older Leaves	Potassium Phosphorus Zinc Copper Molybdenum	Nitrogen Phosphorus Potassium Boron
2/ Disorders Producing Symptoms Mainly On Recently Matured Leaves	Magnesium Nitrogen Manganese Sulphur	Manganese Copper
3/ Disorders Producing Symptoms Mainly On The Younger Leaves	Calcium Iron Boron	Zinc
* Various nutritional disorders were induced in tamarillo seedlings (var. Oratia) grown in water culture using a programmed nutrient addition technique. The plants received non limiting amounts of all essential nutrients except the element under investigation which was applied at a level which either induced a deficiency or a toxicity. The order in which the descriptions of the individual nutrient disorders appear in this table is based on the leaf position where the symptoms first appear, that is, older leaves; recently matured leaves; and the youngest leaves. Within each of these groupings, the disorders have been further ranked according to the ease with which they were induced.

References

INTRODUCTION

The tamarillo (Cyphomandra betacea (Cav.) Sendt.) is one of New Zealand’s more recent commercially produced subtropical crops. Prior to 1967 tamarillos were known as “tree tomatoes”, but the name was changed to be more appealing to potential export customers, and to avoid confusion with the common tomato (Lycopersicon esculentum). Tamarillos require a very mild climate which limits their commercial production in New Zealand mainly to Northland, Auckland and the Bay of Plenty (Table 1). In 1973 there were about 250 ha of tamarillos grown commercially but this area increased to just over 400 ha in 1983 and dropped back to 325 ha in 1992. The majority of these plantings are of the large, red skinned varieties such as Oratia, which are more popular than the yellow skinned type.

Under suitable conditions tamarillos can yield from 15 to 17 tonnes/ha in commercial orchards. To maintain maximum production of quality fruit it has been found that fertiliser, particularly nitrogen needs to be applied periodically throughout the growing season. Tentative maintenance fertiliser requirements for mature plants are given in Table 2.

Up to the present time little attention has been given to the diagnosis of nutritional disorders in tamarillos. Experience with other crops such as kiwifruit has shown that visual symptoms can play an important part in diagnosing nutrient deficiencies and toxicities in the field. Clearly recognisable leaf symptoms associated with a specific disorder usually appear only after metabolic functions in the plant have been seriously disrupted and losses of yield already sustained. Thus, the presence of visible leaf symptoms usually indicates that a serious problem exists. This article describes visual symptoms of nutrient disorders in tamarillos so that they can be distinguished from non-nutritional causes. Accurate diagnosis is important if nutrient disorders are to be dealt with effectively. Thus, confirmation of any visual diagnosis needs to be supported with evidence from plant and soil analysis. Although critical leaf concentrations for tamarillos have yet to be determined, some indication of the concentration of individual elements required in the leaf can be gauged from the results in Table 3 and from the results given in this article of concentrations found in leaves of plants showing clearly recognisable symptoms of deficiency or toxicity.

Seasonal trend data is now available for Tamarillo leaf samples. Samples may be taken any time during the growing season and compared to optimum ranges.

Leaf samples should comprise 25 youngest fully expanded leaves (plus petioles) collected randomly from the monitor block.

For monitoring, leaf samples should be taken at the same each year to compare.

If nutrient disorders are suspected, leaf samples may be taken as soon as the problem is noted. It is preferable to include a second leaf sample from unaffected plants.

REFERENCES

Agricultural Research and Advisory Services Divisions. Ministry of Agriculture and Fisheries (1986). Fertiliser Recommendations for Horticultural Crops. First Edition pp 31.

Asher, C.J. and Cowie, A.M. (1970). Programmed nutrient addition - a simple method for controlling the nutrient status of plants. Proceedings Australian Plant Nutrition Conference, Mt Gambia, South Australia. 1b, 28-32.

Fletcher, A.W. (1975). Growing Tamarillos. New Zealand Ministry of Agriculture and Fisheries Bulletin.

Horticultural Market Research Unit (1985). Exotic Fruits (Pepino, Tamarillo, Feijoa, Passionfruit, Frozen Kiwifruit) Japan Horticultural Market Study 1984-85 pp 15.

Sale, P.R. 1985. Management Aspects of Tamarillos. New Zealand Fruit and Produce Journal (September/October) 17-20.

Smith, G.S.; Asher, C.J. and Clark, C.J. (1985). Kiwifruit Nutrition. Diagnosis of Nutritional Disorders.