Blue Heliotrope
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NSW DPI primefacts PROFITABLE & SUSTAINABLE PRIMARY INDUSTRIES www.dpi.nsw.gov.au JULY 2008 PRIMEFact 653 (REPLACES AGFact P7.6.57) Blue heliotrope JJ Dellow Former Weeds Agronomist, Orange Agricultural Institute CA Bourke Principal Research Scientist (Poisonous Plants), Orange Agricultural Institute AC McCaffery Project Officer (Weeds), Orange Agricultural Institute Introduction Blue heliotrope (Heliotropium amplexicaule Vahl) is a summer-growing perennial herb. It is extremely drought-hardy, which increases its ability to persist and spread, and has made it a major agricultural weed in NSW. Blue heliotrope belongs to the Boraginaceae family which includes forget-me-nots (Myosotis spp), comfrey (Symphytum officinale), Paterson’s Figure 1. Blue heliotrope flower. Photo: J. Kidston curse (Echium plantagineum) and yellow burrweed (Amsinckia spp). to a wide range of soil and climate types. It occupies Blue heliotrope is a native of South America, and was more than 110 000 hectares in NSW. probably introduced to Australia as an ornamental plant in the latter part of the 19th century. It was first reported in NSW in 1908 in the Hunter Valley, and Habitat since then has colonised large areas of NSW. Blue heliotrope is often found along roadsides, in Blue heliotrope is a noxious weed in many local waterways, on non-arable country, in degraded control areas of NSW. pastures and on fallowed cultivation. Major infestations occur in areas receiving more than 500 mm of rainfall per year, although it is also Impact established in low-rainfall areas, such as the western Blue heliotrope competes with desirable pasture districts of NSW. plants and causes toxicity to stock. It is widespread because it is a highly persistent perennial, adaptable Description Life cycle Blue heliotrope is a hairy, summer-growing, prostrate The plant is adapted to a wide range of habitats, and perennial herb, 15–30 cm high and 30–200 cm in can reproduce from both seed and root fragments diameter. that occur throughout the soil profile. Flowering is largely dependent on rainfall, but usually starts in November and continues through summer until March. In frost-free areas, the plant is capable of growing and flowering at any time of the year after rain. Figure 2. Blue heliotrope seedling. Photo: J.J. Dellow. Stems It has many hairy, branched stems radiating from a woody rootstock, and is highly aromatic. Blue heliotrope has a strong, slender taproot that can be very woody. It generally extends to over 1 m, but has been observed at up to 2 m throughout the soil profile, with a complex system of lateral roots occurring at several depths. Figure 4. Mature plant. Photo: J.J. Dellow. Leaves The leaves are alternate, dull green, soft and tapered Established plants produce a flush of new growth at both ends. in spring and autumn, flowering profusely at these Flowers times. In warmer areas, plants may flower and set seed as early as July. The flowers are bluish-purple with yellow centres. They grow in dense clusters along one side of a The plant is frost-susceptible, dying off in winter and coiled stalk, often referred to as a fiddle neck. regenerating from the vigorous root system in the following spring. The fruit develops into two nutlets, each containing two seeds. Spread Blue heliotrope spreads aggressively, as it produces many sticky seeds that adhere to animals and machinery. Seed can pass unharmed through the digestive tracts of most animals. Blue heliotrope can also regenerate from root fragments. It is most commonly spread by road graders, farm machinery, livestock, humans and the movement of water along watercourses. Figure 3. Fiddle neck and flower of a mature plant. Photo: R. Medd and B. Auld. 2 PRIMEFACT 653, BLUE HELIOTROPE Toxicity It is necessary to reduce the weed density using systemic herbicides before sowing a competitive Blue heliotrope contains pyrrolizidine alkaloids (PAs). perennial pasture. Advice on pasture management These PAs are also found in common heliotrope (Heliotropium europaeum). The amount of PAs in blue can be obtained from your local agronomist. heliotrope is much higher than in common heliotrope. Heliotrope is not very palatable to livestock, and Grazing management consequently tends to be avoided; however, some Where large infestations of heliotrope occur, individuals continue to eat it indiscriminately. sheep and goats can be used to manage heliotrope, Heliotrope will be eaten if no other feed is available. provided a different group of animals is used Continual ingestion by livestock of large amounts of each year. heliotrope plants (either fresh or dried), or of their The sheep rumen has a great capacity to degrade seeds as contaminants in stock feed, can cause liver most of the poisons present in the plant. The merino damage and reduced productivity (see Table 1). In has the greatest tolerance of heliotrope, but adult order of susceptibility, horses, pigs, cattle, sheep and goats can all be affected, with horses being the most wethers should be used rather than breeding ewes susceptible. or juveniles. British breed crossbred sheep are less selective grazers than merinos, and are more All affected livestock species may become jaundiced frequently affected by heliotrope poisoning. and experience varying degrees of photosensitisation. Anecdotal evidence suggests that supplementing sheep with molybdenum and sulfate can reduce Management and control the chronic health effects of heliotrope poisons. The Eradication of blue heliotrope is difficult. The effective combined effect of molybdenum and sulfate is to control of this weed will usually involve a combination reduce the accumulation of copper in the animal’s liver. of the following options. The aim of this practice is to either improve the short- term heliotrope tolerance of crossbred sheep or to Pasture management allow the same group of merino sheep to be used to Overgrazing, which reduces competition from graze the plant over two or three successive seasons. pasture, is a major cause of heliotrope infestation. Correct grazing management to reduce PA toxicity is Managing grazing pressure is critical to the control of even more critical if Paterson’s curse is also present. this weed. In this situation, stock can be exposed to PAs during Maintaining a vigorous summer-growing perennial summer from the heliotrope and during the cooler pasture to out-compete heliotrope provides effective months from the Paterson’s curse, increasing the risk long-term control. of toxicity occurring from prolonged grazing. Table 1. Summary of livestock toxicity symptoms Animal Clinical Symptoms Production Effects Pathology Horses • Weight loss Reduced productivity Liver damage and secondary • Dull brain damage • Depressed • Uncoordinated • Wander aimlessly • Can develop respiratory difficulties • Death Pigs • Death Liver, kidney and lung damage • Depressed Liver damage and secondary Cattle • Unpredictable bouts of aggression Reduced productivity brain damage • Death • Can accumulate copper, which can Sheep, Goats Reduced productivity Liver damage cause sudden death when released. PRIMEFACT 653, BLUE HELIOTROPE 3 Biological control Biological control, if successful, has the potential to reduce the long-term economic and environmental costs of traditional herbicide control methods for blue heliotrope. There has only been one biological control agent released in Australia for blue heliotrope. The blue heliotrope leaf-beetle (Deuterocampta quadrijuga) was first released in Australia in 2001. At high densities, leaf-beetles can completely defoliate blue heliotrope, with both the larvae and adults feeding on the leaves. The blue heliotrope leaf-beetle has the potential to build up population levels rapidly, as each beetle lays several hundred eggs. Figure 5. Blue heliotrope flower. Photo: J. Edwards Horses, pigs and cattle should never be used in the grazing management of blue or common heliotrope. Cultivation Cultivation gives short-term control, but also has the potential to spread the problem. To reduce the establishment of new plants from root fragments, it is best carried out after application of a systemic Figure 6. The blue heliotrope leaf-beetle herbicide. Follow-up seedling control is essential. (Deuterocampta quadrijuga). Photo: A. Johnson. Chemical control Legislation Systemic herbicides play a critical role in the control of blue heliotrope, by helping to destroy their root system. Blue heliotrope is a Class 4 noxious weed under the NSW Noxious Weeds Act 1993 in many areas of Only a registered herbicide, used according to NSW (see Figure 7). the directions on the label, should be used to control a weed. Class 4 control requirements are that ‘the growth and spread of the plant must be controlled according Refer to the NSW DPI Noxious and environmental to the measures specified in a management plan weed control handbook for the recommended published by the Local Control Authority’. chemicals to control blue heliotrope. The responsibility for control of noxious weeds on To improve the effectiveness of chemical control, private land rests with the landowner or occupier of herbicides should be applied to blue heliotrope when the land. it is actively growing and commencing flowering (late February to March). A full list of noxious weeds and requirements under the NSW Noxious Weeds Act 1993 can be found at Avoid spraying stressed plants. www.dpi.nsw.gov.au/weeds PRIMEFACT 653, BLUE HELIOTROPE 4 v LIGHTNING RIDGE v TAMWORTH v COBAR v BROKEN HILL v DUBBO v SYDNEY WAGGA WAGGA v Control Class 4 Figure 7. Areas of NSW where blue heliotrope is declared a Class 4 noxious weed. Acknowledgements © State of New South Wales through NSW Department Information for this Primefact was taken from: of Primary Industries 2007. You may copy, distribute and otherwise freely deal with this publication for any purpose, • Da Silva, E 1991, ‘The ecology and control of blue provided that you attribute NSW Department of Primary heliotrope (Heliotropium amplexicaule Vahl)’, Final Industries as the owner. Report. ISSN 1832-6668 • The work done by Royce Holtkamp, Jim Dellow, Replaces Agfact P7.6.57 Graeme Kelso and Barney Milne, NSW Agriculture.