Introduction
Capsicums (Capsicum annuum) and chillies (Capsicum frutescens) originate from South and Central America. They are members of the Solanaceae family, as are tomatoes, potatoes and eggplant. Plants are bushy, about 60–80cm high and semi-perennials that are grown as annuals in commercial cultivation. They supply good levels of antioxidants and vitamin C.
Capsicum and chilli varieties are many and produce fruit with a wide range of shapes and colours. Chilli varieties range widely in pungency.
In Western Australia, the name capsicum is used for fruit which is bell or cone-shaped with a sweet flavour. The same fruit is called bell pepper or sweet pepper in the USA and Britain.
The term chilli refers to fruit which is usually cone-shaped and smaller and the pungency may be mild to intensely hot. The main compound responsible for pungency is capsaicin. Within a chilli variety, the greatest pungency is with small, red fruit, especially in the cross-walls, close to the seeds and pith area.
Capsicums are used in salads, baked and stuffed dishes, stews, stir-fries, salsa, pizzas and cheeses, pickles and for stuffing olives. They may also be used for producing paprika which is used for colouring foods, flavouring and in sauces.
Chillies are the most important spice crop in the world. They may be used fresh, in pickles, sauces, salsa, pizzas, flavouring and pastes. There is an increasing demand in Australia for new ways of using chillies for culinary use.
Capsicums are marketed throughout the year in Western Australia. In 2013/14, Western Australian capsicum production was about 10 000 tonnes (DAFWA estimate). Average yields are close to 25 tonnes per hectare, although commercial yields of more than twice this are achieved.
Wholesale prices vary with season and time of year. Prices are higher for red capsicums that take longer to produce than green ones. Returns for Carnarvon capsicums that are harvested during winter and spring are generally higher than for Perth crop.
Most capsicums and chillies are grown in soil, using trickle irrigation and polythene mulch, however production of very high quality capsicums in protected cropping systems using hydroponics is increasing.
Climate
Warm conditions over a five month growing period are necessary for high yields and good quality fruit. Capsicums and chillies require slightly warmer temperatures than tomatoes or cucumbers. Chillies are more tolerant of high temperatures than capsicums. Optimum temperatures for fruit set are between 16°C and 21°C. For good fruit development, night temperatures of 15–17°C and day temperatures of 24–30°C are ideal.
Capsicums can be damaged by frost. Plants retarded by cool weather tend to harden and seldom regain the vigorous growth necessary for high yields. During cold weather, the fruit remains small, hard and malformed because of uneven pollination. The fruit may also have numerous growth cracks.
The fruit may be sun-scorched during hot weather and fruit will show poor setting and poor colouring when temperatures are above 33°C.
Soils
Soils must be well-drained, with optimum pH of 5.0–6.0 (measured in calcium chloride) and low salinity.
Varieties
Most commercial varieties are hybrids. Varieties have a primary mature colour that is usually green, but may be yellow or purple. They also have a secondary mature colour that is usually red, but may be orange or yellow or other colours. Fruit picked at this stage is much sweeter than green fruit and has more pro-vitamin A. There are also black, cream, brown and lime coloured varieties.
New varieties are always being introduced, so check with your local seed supplier or nursery. These varieties may be more resistant to disease, produce higher yields of fruit, produce more uniform fruit or be more suited to the latest market requirements for quality. Before planting new varieties on a large scale, compare them in small plantings to existing varieties under the same growing conditions.
Chillies
Growers produce a range of varieties as well as standard chillies such as Firefly (9cm long and 1.5cm wide). These include the hottest variety, Habanaro, and the most well known world variety, Jalapeno. They may also include oval chillies such as Cherry Bomb and small chillies such as Cascabella.
The pungent small mature green (primary colour) or red (secondary colour) chillies are in most demand. Long sweet yellow type varieties are grown on a small scale and are often called ‘paprika’ in Western Australia, but note that this term should be used for dried red capsicums. They are large, compared with most chilli varieties and have a very low pungency when picked at the yellow stage (before ripening to red). There are also orange chillies that have high pungency.
Seedling production
Seedlings may be raised in beds or nurseries by the grower, but are usually ordered from specialised nurseries for delivery in single cell-packs in 8 to 10 weeks.
Transplanting
Transplanting is done by hand or machine.
In Perth, plant early crops from July to September in warm, well-protected areas. Unprotected crops make slow early growth and harvesting is often delayed. Low plastic tunnels or cloches aid the production of early crops. Transplant the main capsicum crop from September to December. Chillies are slower to mature than capsicums.
In Carnarvon, transplant from late February to August. Transplanting early in the year is best so that crops can become well established before the onset of cool weather.
Spacing
The choice of spacing depends on irrigation layout and tractor access for fertiliser application, boom spraying and harvesting. In Perth, a good spacing between plants is 75cm (two rows per bed) by 40 cm which gives 30 000 plants per hectare.
In Carnarvon, space plants in a double row with plants 40cm apart between the rows and 30cm apart within the rows, with row centres at 1.5m apart. Wide spacings allow picking over a long period, while close spacings will give high yields over a short period and better pollination in hot periods.
Fertilisers
Sandy soils
Sandy soils are the main types on the Swan Coastal Plain from Eneabba to Busselton. Phosphorus fertiliser should be applied before planting on all but deep grey sands. The rate of phosphorus should be determined from soil test results.
Trace elements and magnesium should also be applied before planting if not applied in the previous 12 months. There is a wide range of fertilisers available for post-planting use. Discuss the best options for your situation with your local advisor or consultant.
Urea and potassium fertilisers are commonly applied to the soil or by fertigation through trickle irrigation or sprinklers.
Loamy, gravelly and clay soils
In their natural state, loams, gravels and clay soils (found at Geraldton, Jarrahdale and in the south-west of Western Australia) have little available phosphorus. Soil testing before planting should be used to determine that rate of phosphatic fertiliser to apply before planting. Post-planting nutrient programs will vary with soil type and cropping history. Discuss crop nutrient needs with qualified advisors or consultants.
Alluvial soils
Alluvial soils are common in the Carnarvon vegetable growing area. These soils contain adequate phosphorus, potassium and many other nutrients, and only nitrogenous fertilisers may be needed.
Starting three weeks after transplanting, apply 35kg/ha of urea every two weeks, which may be injected into the trickle irrigation system. Crops planted in August respond to foliar sprays of calcium nitrate at 2g/L.
Irrigation
South-west
Capsicums need uniform soil moisture conditions for high production. Dry periods may cause shedding of flowers and young fruits, and blossom end rot on the fruit. During hot weather, water crops in sandy soil twice daily. In warmer months, apply three-fifths of the water in early to mid-morning and two-fifths in early to mid-afternoon. In cooler months, apply all of the water in early to mid-morning.
Water used for irrigation should preferably contain less than 1000 parts per million (ppm) of total dissolved salts, or have an electrical conductivity (EC) reading of less than 180 millisiemens per metre (mS/m).
Apply water to replace 130% of evaporation. To calculate how much water a crop grown on a sandy soil needs refer to the ‘See also’ links on this page.
An increasing area of capsicums is being watered by trickle irrigation in Perth. When combined with black plastic mulch, this results in fewer weeds and a saving in water. It is also useful for capsicums under cloches to increase soil temperatures in cooler weather. However, trickle irrigation may result in more mites and powdery mildew on the plants compared with using sprinklers. There may be two rows of capsicums per cloche, each with its own row of trickle irrigation.
An evaporation replacement factor of 60-90% is suggested for trickle irrigation of capsicums in Perth. Growers may also plant a double row on black or reflective plastic mulch, without clear polythene protection, and water by sprinkler irrigation from planting onwards.
Carnarvon
When using trickle irrigation and polythene mulch, water at 25% daily evaporation replacement rate during early growth and at 40–50% of daily evaporation replacement rate from flowering onwards. Tensiometers may be used for irrigation scheduling to apply irrigation at a suggested soil tension of 30–35 centibars (cb).
Protected cultivation
Early crops are often planted in Perth in July and August and raised in cloches. These provide higher air and soil temperatures, and hasten crop growth, reduce pest problems and give protection from wind, heavy rain and sand blasting.
Cloches have wire hoops at 1.2m apart, which are inserted about 30 cm into the soil and are about 50cm high. A line of wire on top of the hoops helps to support the plastic. The plastic is 1.5m wide and is tucked into the soil. The plastic should be raised on warm days. In late September, the plastic may be removed and the grower then waters by sprinklers or continues with trickle irrigation.
Capsicums may be protected from sunburn and wind by growing under shadecloth (25–40% shade) which may be permanent or placed temporarily on hoops over the crop and moved to one side for harvesting. Shaded crops produce bigger and firmer fruit and increase the packout of premium fruits.
Pruning
Capsicums and chillies generally do not need pruning or support. However, early crops in Carnarvon may need single horizontal wire trellising to prevent damage from storms and wind in winter.
After the first season’s growth, some growers prune back capsicums to major branches and allow them to re-grow. This is not good practice, as yields are lower in the second year and frequent spraying is needed for pest and disease control.
In Carnarvon, crops planted in March are sometimes cut back in August/September with a slasher or brushcutter in order to give a second crop in November/December.
Pests and disease
Capsicums and chillies need frequent monitoring to produce good yields and fruit quality. This especially applies to Carnarvon, where regular spraying may be needed during certain seasons to control major pests such as aphids on the whole plant, grubs on the fruits and powdery mildew (Leveillula taurica) and bacterial spot (Xanthomonas campestris) on the leaves. Caterpillars and aphids are the major pest problems in Perth.
Capsicums are also affected by soil-borne diseases such as Fusarium rot, Sclerotinia rot, Rhizoctonia stem canker, and root knot nematode. Crop rotation is therefore recommended, with an interval of three years between capsicum crops.
Capsicums are susceptible to viruses, for which there is no direct control. Tomato spotted wilt virus has been more common in Western Australia in recent years and is spread by thrips. Cucumber mosaic virus is spread by aphids and has caused severe damage to capsicum crops in Carnarvon in recent years.
Check with the Australian Pesticides and Veterinary Medicines Authority (AVPMA), resellers, advisors and current chemical labels for the latest options for pest contol.
In unshaded areas, exposed fruit, especially at the red stage, may be unmarketable because it is sunburnt.
Hot weather, high nitrogen and low watering may increase losses from blossom-end rot which appears as sunken brown spots on the sides or end of the fruit. A shortage of calcium is also associated with blossom end rot and growers may spray calcium nitrate at 2g/L in summer to help minimise this.
Weed control
Capsicums have a long period of cropping but do not cover the ground well. Good weed control is therefore essential to aid insect and disease control and harvesting. There are no registered residual herbicides and capsicums are sensitive to these. Black or reflective plastic mulch will control weeds, except in the planting holes. If plastic mulch is not used, much hand-weeding will be necessary.
Fruit set
Capsicums are mainly self-pollinating and do not need bees for pollination. Green fruit is mature for picking 30-35 days after flowering and red fruit takes a further 20-25 days. Pollination may be poor in hot or cold weather, after mositure stress, when the humidity is too low and in high winds.
Fruit is ready for harvesting 10–15 weeks after planting, depending on season and stage of maturity required for market.
Harvesting
Capsicums or chillies are cut or carefully snapped off by hand and the stem is trimmed with secateurs or a knife. Avoid damaging the shoulders of the fruit and the branches, as this may lead to bacterial soft rot. Capsicums may be picked at the mature primary or secondary colour stages. This gives more flexibility in harvesting compared with most crops. Harvest at 7 to 21-day intervals depending on the season and the need to pick.
Pick capsicums at the mature primary stage (usually green), when they are firm, with thick walls and dark green. If picked too early, they have thinner walls and are inclined to wilt. If desired, capsicums can be left on the plants to the secondary stage (usually red) before harvest. At this stage, they are sweeter, but not so firm. Also, yields may be reduced by 25–50%, but prices at the secondary stage are usually higher than for fruit at the primary stage. You can pick only fruit of one colour, or pick both colours.
Once the initial fruit has set, few additional flowers will set until the first fruits are picked. The heaviest crops are from the first three picks. Some pickers are allergic to chillies.
Yields of capsicums usually vary between 10 and 30t/ha, but yields of 50t/ha are not uncommon, with some of the highest yields up to 80t/ha.
Storage
Cool the fruit with forced-air cooling or by vacuum cooling. Store at 7–10°C and 90–95% relative humidity for up to three weeks. Fruit which is to be stored for some time must not be stored with fruit such as tomatoes and apples which will give off ethylene gas and reduce the storage life. Green fruit has the longest storage life.
Marketing
Machines are available that will wash, brush and grade capsicums for size. The fruit also need to be visually graded for colour, so the package contains fruit only of one colour. They may also be voluntarily graded into special or premium and No. 1 grades. Fruit are preferably packed on their sides in cartons, but plastic returnable containers are also be used for marketing. Chillies may be packed into small ventilated 1kg polythene bags with eight bags per carton or into trays.
About three-quarters of capsicums are sold as green fruit, and the remainder are a mixture of colours, mainly red, but yellow and orange are also popular. Most chillies are sold as red fruit.
Fruit which is turning from one colour to another should not be picked. Fruit will not change colour after harvesting. However, to obtain higher prices, some varieties may be red-ripened with ethylene gas providing the fruit are gassed at the 30% ‘chocolate or turning’ stage.
Imports of capsicums are significant from eastern Australia and overseas if there is a shortage from Western Australian growers. There is also flexibility in time of picking. For these reasons, very high prices are generally not received for capsicums.
Capsicums and chillies are not exported to overseas markets from Western Australia.
Paprika
Most paprika is imported. Red capsicums are dried with forced-air heaters and ground to a fine powder to make paprika. Strict attention must be paid to hygiene. Oleo-resins may also be distilled from paprika and used in pharmaceutical products.
Acknowledgements
The original version of this material was authored by Harry Gratte, Margaret Graham and John Burt.