Fertiliser
Young plants respond to moderate levels of nitrogen and potassium but their phosphorus requirements are very low. Apply trace elements, particularly iron, every two to three years or as required. Leaf analysis should be carried out each year for the major species grown.
Apply fertiliser mainly during vegetative growth. Rates to apply will depend on plant vigour, the site’s fertiliser history and soil type. The options for fertilising include slow release nutrients, liquid feeding and solid fertilisers.
Slow release
Place low phosphorus (P) slow release fertilisers next to the plant at label rates, two to three times per year during active vegetative growth.
Liquid feeding
Apply a solution containing 75 parts per million (ppm) nitrogen (N), 5ppm phosphorus (P) and 50ppm potassium (K) weekly during active growth. The ammonium form of nitrogen is suggested. Further information on preparing liquid fertiliser stock solutions is available.
Solid fertilisers
Three applications of ammonium sulphate at 50kg/ha are used in South Africa with the first at the start of active growth and then at three to four week intervals. Three applications of muriate of potash of 30kg/ha may also be applied at similar intervals.
Irrigation
Irrigation or rainfall is essential for successful establishment and early plant growth. As a general guide, irrigate to replace at least 40% of evaporation. This equates to 2 to 12 litres of water per plant per day, depending on the weather and plant size.
In sandy soils during late spring, summer and autumn, regular irrigation is suggested. Tensiometers can be used to help in scheduling irrigation.
Pests and diseases
The most important disease in Western Australia is caused by the fungi Phytophthora spp., commonly known as dieback. Phytophthora affects the plant root system and crown and has the potential to kill plants at any age.
The plants may die suddenly (sudden death syndrome), or become chlorotic (pale) and grow poorly in the early stage of infection. Infected plants usually wilt during periods of water stress.
To minimise the risk of introducing or spreading phytophthora, buy disease-free plants and take basic quarantine measures. Plants showing early symptoms have been treated with appropriate fungicides with some success. Refer to the APVMA website for current information on registered chemicals.
Other diseases include colletotrichum (on Protea spp. and Serruria florida), drechslera (mainly Leucospermum spp.), elsinoe (Leucospermum spp., Leucadendron spp., Serruria florida), botrytis (all species), batcheloromyces leaf spot (Protea cynaroides), bacterial leaf spot (Protea cynaroides) and alternaria leaf spot (Protea, Leucospermum and Leucadendron spp.).
All of these diseases, their symptoms and control measures are covered in Protea Diseases by Sharon von Broembsen.
The major insect pests, mainly for Leucadendron species, are the stem boring and leaf eating weevils. Black beetle and termites can also cause sporadic damage. Birds, especially parrots, can cause serious damage in some areas.
In addition to physical damage, insects such as stem borers, thrips, mites, scale and various beetles can cause quarantine problems on export markets.