DURIAN CULTURE

SCIENTIFIC NAME: Durio zibethinus
FAMILY: Bombacaceae

I have no doubt we can grow Durian and produce fruit in north Queenland. However there are some very important factors in successful culture.

Propagation
Seedlings best in a fairly light mixture - e.g. 1 part topsoil loam plus 3 coarse sand and one peat moss or well-decomposed compost (by volume). Graft either wedge, whip and tongue or modified forkert bud graft. Spring (September/November) best time for wedge or whip and tongue. Graft to leave at least 12 rootstock leaves on below the union. Scions - fairly mature wood (light brown or grey and minimum of 5 mm diameter with minimum of 4 plump viable buds. Remove all scion leaves and cover graft with poly bag. Bottom heat under bag to give soil temperature 25° to 30° C in bottom of medium is desirable. Keep plants in light shade and fairly dry until scions develop 150 mm of new growth. For unsterilised soil, may require prophylactic drenches (Ridomil 5 g per m2) or Aliette sprays to prevent Phytophthora root rot. Apart from Phytophthora-resistant rootstocks (D. lowianus etc.), seedlings of the cultivar Chanee are favoured as rootstocks in Thailand.

Planting Site
A well-drained loam or sandy loam is desirable. Plant on mounds (e.g. gently sloping 2 m across and 200 mm high). Provide diversion drains uphill to exclude all water from outside coming into the Durian area. Plant on mound - soil level the same as in the container. Over deep planting or allowing plants to sink can be fatal. Plant at least 7 m apart.

Shade
Essential for at least the first 2 years. Sarlon (32% adequate) over top and sides - enclosure at least 2 metres high. Remove in mid-winter 18 months to 2 years after planting. However at planting - plant 2 or 3 shade trees together 1 to 2 metres from Durian on western side. Leucaena leucocephala is suitable. Remove branches of shade tree interfering with durian growth and shade can be gradually cut back to eventual removal at 3 to 4 years.

Windbreaks
Cyclone and strong wind protection essential - particularly on south eastern side of block - and provides more suitable microclimate. Also - stake and tie durian trees for at least first 3 years.

Mulching
Plant material - straw, peanut, bagasse over the root zone beneficial - but animal and bird manures reputed to encourage Phytophthora root rot. Apply mulch at end of 'wet' - sufficient depth only so that nearly all will be decomposed by start of next 'wet'. Keep mulch at least 600 mm away from the durian stem.

Fertilizer
Minimal in first 2 years - only sufficient to keep tree growing vigorously. Trace elements may also be required. Keep fertilizer away from foliage and spread around dripline - place no closer than 300 mm to plant stem at any stage. Suggest 200 g of superphosphate in and around planting hole - but not in contact with exposed roots of the tree when planting.

In April, August and December, apply 100 g of mixture approx. N.P.K. - 10:2:17 (Q7) per tree per year of.age - e.g. in 3rd year - 300 g per tree per application. Each February, apply 100 g of Ammonium nitrate or Urea per tree per year of age. Each August - apply 0.5 kg of Dolomite per tree per year of age.

Irrigation
Essential in north Queensland - under-tree sprinklers best. High water requirement after flowering and during fruit development. However Chanee variety requires less at flowering; excessive water leads to poor set and fruit drop.

Varieties - (Cultivars)
We (K.H.R.S.) have had much better growth and less disease problems with the Thai varieties - Chanee, Chompoo Sri, Gob, Gaan Yaow and Montong (particularly Chanee which appears to like our environment) than those from Malaysia (D96, D24, D123, etc.) However this comment is not conclusive - and there may well be individual varieties from a number of countries which suit this area. Insufficient numbers of varieties have yet been examined.

Flowering
Peak flowering on seedling trees in north Queensland has occurred in the October - December period, but information on cultivars is not yet available. a November flowering should give a March/April harvest (4 to 5 months fruit development). Chances of obtaining successful pollination on single trees appears remote, although the Thais say that some of their varieties are self-fruitful (pollen from the stamens of one flower, transferred to the pistil of that flower or to another flower on the same tree resulting in fruit set). Best bet is to plant at least 2 seedlings or 2 different varieties (hopefully coinciding in flowering period) together. Obviously a larger block of 6 to 10 or more trees would even be better. It appears we have at least one species of fructiverous bat in north Queensland capable of pollinating flowers. Also the common flying fox may be of use. Hand pollination at night (with pollen from flowers on another tree) is another possibility if one wishes to persevere.

Pests
Keep vigilant for the black beetle (Rhyparida spp.) in particular. Carbaryl is suitable as a safe, efficient knockdown chemical.

Diseases
On some varieties, leaf fall as a result of infection with anthracnose (Colletotrichum gloeosporidioides) is a problem. Malaysian varieties appear to be more susceptible than the Thai ones. We have lost trees with root and trunk rots - Macrophomina phaseoli in particular. Possibly Phytophthora palmivora (root rot) will be a serious problem - as it is in Asia. During wet season and autumn suggest drench soil around roots with Ridomil (5g per m2) and/or spray foliage with Aliette. Drench at 2 month intervals.

Watch for lesions on trunk and clean out and paint-damaged areas with a mixture of Cuprox and hydrated lime (50/50) as a slurry. You can inarch one or two seedlings for additional root rot resistance and tree stability. After 1 year of field growth - remove branches below 600 mm from soil surface and paint all pruning cuts with Cuprox/lime slurry.

KEY POINTS

GOOD SOIL DRAINAGE
ADEQUATE SHADE - FIRST TWO YEARS
PEST AND DISEASE CONTROL
B. J. Watson, Senior Horticulturist
Kamerunga Hort. Research Station

DATE: March 1981

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