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.