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New Zealand Citrus
By Nick Sakovich
New Zealand means the island of the long cloud. It is a land with ample rainfall which produces beautiful, lush plant growth and magnificent scenery. Although this past year, while we were drenching in El Nino, New Zealand was in the midst of a drought and record breaking heat. The lush greenery turned to a landscape typical of southern California in July. All in all, it is a beautiful country, well worth visiting, with friendly people, plenty of open space, lots of cattle, sheep and good agriculture, and with a pace of life a little slower than ours and a lot less hectic.
New Zealand has a citrus industry, although it is a small one. It was developed largely to meet domestic needs, but recently has found some profitable export markets. Total planted acreage is estimated at 4,000 to 5,000 acres, with annual production at 25,000 - 30,000 tonnes. There are about 700 citrus growers, many of them growing other fruit crops. Of these 700 growers, the highest number is concentrated in the 0-5 acre range, with the next concentration at 6-15 acres. There are only 17 growers producing fruit on land larger than 25 acres. A few growers own properties in the 75-300 acre range.
The citrus growing regions are located on the north island in three different areas: a) the Northland (Kerikeri region) - specializing in mandarins (especially Satsuma), with some lemons and Navel oranges; b) Bay of Plenty, specializing in the New Zealand grapefruit, Seminole tangelo and lemons; and c) Poverty Bay (Gisborne), producing Navel oranges with some mandarins and lemons. Small plantings are also located just north and south of the city of Auckland.
Temperature extremes are rare. Some radiation frosts can cause damage to fruit. High annual rainfall is common to New Zealand citriculture, so much so that some farms have no irrigation systems. However, this wet environment is also conducive to severe rind blemishing, fungal diseases.
In the citrus growing districts, the maximum January temperatures (summer) average around 24 degrees C, with the average minimums at 13 C. July maximums (winter) are around 14 C with average minimums are 5-6 degrees C. Annual rainfall ranges from 42 to 67 inches.
One major problem for New Zealand citriculture is the low accumulation of annual heat units. These are necessary in order to obtain adequate sugar (Brix) levels . Orlando, Florida produces 3700 annual heat units, Riverside 1700, Valencia, Spain 1600, but in New Zealand annual heat units range from the low 700's to the high 800's. It is obvious that certain varieties of citrus like grapefruit and the Valencia orange will not do well with this low production of heat, and other varieties like lemons and Satsuma will do very well. Of particular importance is the choice the proper rootstock to help obtain good interior fruit quality.
It was only in the 1950's, with the introduction of the trifoliate rootstock, that New Zealand was able to advance beyond its traditional production of lemons and the New Zealand grapefruit ( a pummelo mandarin hybrid). Today, the citrus industry is primarily made up of Mandarins, lemons, Navel oranges, Tangelos and selections of the New Zealand grapefruit - all entirely on trifoliate rootstock.
New Zealand is in the midst of establishing a serious lemon export industry, mainly to Japan. Since their season is opposite ours, they are in an excellent position to export high quality lemons during the high priced summer months. The potential is their, but an important first steps to be taken is the selection of the proper cultivars suitable for international trade, along with the appropriate rootstocks for high yields and good fruit quality. However, the importation and testing of this plant material is costly. Government probably will not pay the bill and therefore it will be up to the growers.
In the past, Villafranca was the predominant lemon cultivar, with sweet orange as the rootstock. Many lines are infected with exocortis.
Yen Ben is a Lisbon selection originating in Queensland, Australia and is now the cultivar of choice for export plantings. This fruit has been well received in the Japanese market. One problem though, the trees tend to have large fruit sets resulting in small sizes.
The Meyer lemon is also grown commercially, although the fruit is not well received in the Japanese market, and it does not ship or store that well.
With the wide range of cultivars available in New Zealand, one can harvest mandarin fruit almost year around. The early satsumas begin in May (remember the seasons are opposite), with the Encores finishing in the October through March period. Several attractive attributes - seedlessness, ease of peeling, good disease resistance and an early to midseason harvest period - have made the Satsumas, New Zealand’s most important domestic and export mandarin. Problems such as alternate bearing, puffiness, small size and blemished fruit can all be overcome. Over the past few years, the early varieties of Miyagawa, Miho and Okitsu have been extensively planted for the export market.
An old selection of Clementine has been grown in New Zealand for many decades, establishing itself in the local market. Of the new cultivars of Clementine from Spain and Corsica, Corsica #2 is the most promising.
An old California variety, Encore, has become quite a good mandarin for New Zealand. Fruit can be harvested over a 5 month period without loss of flavor or juiciness. The flavor is excellent, but alternate bearing and blemished fruit are a problem.
The Seminole tangelo has been planted since the ‘60's, mainly for juice production.
New Zealand produces rich flavored Navel orange fruit which mature late July through November. There is stiff competition from imports of good quality Australian navels.
One factor holding back the New Zealand citrus industry is it’s use of predominately one rootstock - trifoliate orange (Poncirus trifoliata). This does not leave any options open for growers when certain cultural issues arise such as compatibility, small fruit size and fruit acidity. More rootstocks need to be tested to give growers choices when faced with diseases and cultural problems - let alone, to improve yields.
There are a few notable differences between the New Zealand citrus orchard and ours. One such difference occurs in Satsuma orchards where the crop is thinned by hand. In fact, if need be, thinning may occur 2 or 3 times. Some hand thinning is also done in Clementine and Encore orchards.
As one looks out over the citrus landscape a quite visible difference is noted in the use of windbreaks. Instead of a single row of windbreaks cutting across the orchard, the windbreaks, or shelters in New Zealand are used to completely wall off a block, thus creating a room effect. These ‘rooms’ may only be 5-12 acres ( a few I saw were only 2-3 acres). In addition to wind control, the main objective of windbreaks is to improve the orchards microclimate. For every 3 feet of height, summer maximum temperatures increase by 0.1 degree C. The different species of windbreaks include: Cryptomeria japonica, eucalyptus (saligna and botriodes), poplars, casuarina and bamboo, with the two latter now being avoided because of competitiveness.
High density plantings - are now being establish with Satsuma mandarins. Tress are planted on a 3 x 6 foot pattern, with every 4th row open to allow machinery access. Crowding becomes apparent after 6-7 years, when complete rows are removed, and when necessary, trees within the remaining rows also removed. The resulting spacing is 3x12 or 6x12. Successful transplanting of the 6-7 year old trees that have been removed is feasible with hydraulic machinery.
The use of white reflective mulches is now standard practice in satsuma orchards where it is used to improve uniformity of fruit coloring and increase Brix levels. It is an expensive practice. The most common material used is Du Pont’s Tyvek, which is laid under the tree canopy 3 months prior to harvest and removed just before or after picking.
Although willing, New Zealand farmers have not yet made the transition to Integrated Pest Management. Many are still spraying with harsh pesticides on a calendar schedule. An important step in establishing an IPM program is the release of beneficial insects.
Although one can find beneficial insects in the orchard, more effective and specific beneficials are needed. But a major stumbling block is the governments reluctance to import such insects.
Discussing the future problems of New Zealand agriculture is very similar to discussing our own problems. Most notable of these is the encroachment of urban life on farm land. Agricultural land prices have risen dramatically. The ability of the grower to repay the purchase cost is now extremely marginal. Newcomers are dependent on regaining capital when the property is resold. (Sound familiar?)
With the increase in urban populations near farming operations, one of the major complaints is pesticide drift. The environmental lobby in New Zealand is strong. In the long run, the agricultural industry will have to become more dependent upon Integrated Pest Management with the emphasis on biological control and the use of ‘soft’ pesticidal sprays.
I would like to thank Andrew Harty of Kerifresh, New Zealand, for his more than generous hospitality. He was a tremendous help in my education of New Zealand citrus. Much of the preceding information was obtained from him either verbally or from his authored papers.