Preparing to grow strawberries

Page last updated: Thursday, 14 April 2016 - 3:53pm

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Soil disinfestation

Most growers apply fumigant each year prior to planting.  Current options include metham-sodium, usually applied broadacre if weeds are bad, prior to 1,3-dichloropropene application or Telone-C35™ applied using shank injection or Rural Inline™, applied through the irrigation.  The latter two are usually applied after beds are formed.  For inline fumigation to be effective the soil must be uniformly moist and compact and the irrigation system must be designed to apply water (and hence fumigant) evenly. If fumigation is uneven then pockets of disease may remain to reinfect the crop.  Be sure to leave adequate time before planting so the chemical can dissipate.  The rates of telone for strawberries are higher than for vegetables at 470-940kg/ha.  Instructions on the label must be followed.

Where irrigation systems are poorly designed and apply water unevenly it is preferable to use shank injection rather than in-line application. On sands, lateral movement of water is very poor and even if emitters are applying water uniformly it is difficult to get even application of fumigant across the bed.  Even using shank injection, tines need to be relatively close together, two tines for a one metre wide bed is not satisfactory in sands.

Since the major disease issue is for growers is fusarium crown rot a mixture of 1,3-dichloropropene and chloropicrin is better than straight 1,3-dichloropropene. Formulations with 35% chloropicrin are in common use but 60% may be better. With repeated use these fumigants become less effective.

Metham sodium is more effective for weed control. It may be wise to rotate fumigants to prolong their efficacy.  Some growers fumigate twice, once with metham sodium and then again once beds are formed with 1,3-dichloropropene and chloropicrin.

Other alternatives may be soil solarisation, biofumigants such as mustards, or soil steaming. None of these are proven under Western Australian conditions, however fewer chemical fumigants are being developed and resistance to them is increasing.  A combination of fumigation methods may be more durable in the long term unless growing out of the ground is a consideration; either in soil-less media or hydroponics.

All fumigant chemicals are highly toxic and must be applied according to the label. Read the label carefully and follow the instructions. Growers need to be licensed to buy and apply 1,3-dichloropropene and its formulations.

Bed formation and plastic laying

Strawberries are usually grown on raised beds covered with black polythene sheet. This provides the plant with deeper soil and good drainage. Black polythene controls weeds, warms the soil faster and promotes fast, early growth so the plants crop earlier.  The fruit is kept clean and because berries are not in contact with soil, there is less rotting.

The soil should be moist before beds are formed. Tractor-drawn implements are available for bed forming and polythene laying. Laying the polythene sheeting when it is warm to hot or during the heat of the day assists in obtaining a firm, stretched appearance, reducing wind damage on new plants.

Beds are spaced according to planting density and at suitable distances for straddling by a tractor and other equipment. Four row beds are common in the Perth area and are usually 1.2m wide with 30cm wheel tracks. Some growers have beds only one metre wide for four rows and others use three or even two-row beds. There are arguments for and against all configurations. Two-row beds are good for speed of harvesting and for spray penetration but less plants can be grown per hectare.

The most commonly used polythene is about 1.7m wide and 25 to 50 microns thick. Slits or holes punched in the plastic aid water penetration. To avoid salt build-up, beds should be no more than 15cm high where sprinkler irrigation is used. With trickle irrigation, beds may be any suitable height. In Florida, 35cm is recommended, the philosophy being to keep all root material within the bed and above the height of the pathways.