CASE NOTES
Green Cestrum (Cestrum parqui)
Bob McKinnon, District Veterinarian, Tamworth RLPB
Posted Flock & Herd February 2011
Taxonomy
Green Cestrum is a member of the Solanaceae family. It is a medium sized perennial shrub growing to 2-3 m. It usually has several light green brittle stems. Its leaves are green and 20 — 30mm wide and 80 — 100mm long and are smooth edged and pointed at each end arranged alternately along the branch. The leaves have a foul pungent smell when crushed. Green cestrum flowers from late spring to autumn. Yellow flowers occur in clusters at the end of the branch. Individual flowers are 20 — 25 mm long and trumpet shaped opening into 5, 6 or 7 small triangular lobes. Clusters of shiny green progressing to black egg shaped berries (7 — 10 mm) are produced during summer and autumn.
Green cestrum is semi-deciduous. They lose most of their leaves during winter and produce a rapid flush of growth in Spring. (The plant suckers quite effectively. In our area it is found as understorey under trees. This is may be due to the frosts inhibiting growth in more exposed locations, or because spread is via bird droppings.)
History
Green Cestrum was imported from South America (native of Peru and Chile) as an ornamental shrub. Green Cestrum is a noxious weed throughout NSW and Queensland.
Poisonous Principle
Two alkaloids, parquine and solasonine, have been isolated from green cestrum and it is thought that these could be responsible for the toxic effects 30g wet weight of plant material /Kg bodyweight killed one experimental calf within 48hrs, while a dose of 11 and 17 g/kg caused dullness and anorexia lasting for 2 days (McLennan MW et al. AVJ 1984 (9) 289 — 291.) Plants vary considerably in toxicity.
Palatability
The plant is usually eaten when other fodder is scarce. Herbicide treatment increases palatability.
Species affected
Green cestrum is toxic to animals including cattle, sheep, horses, humans, pigs and poultry. Its effect on native fauna is unknown. In our situation it is most often seen as a disease of cattle.
Clinical signs
There may be alternating depression and mania, fever, loss of appetite, ataxia, depression, recumbency, tendency to charge, convulsions and death. Many cases are just found dead without any prior clinical signs being noticed.
Death may take between 24 hours and 3 days depending on the animal, time of year and amount of green cestrum eaten.
Gross Pathology
Green cestrum poisoning in cattle is a primary hepatotoxicity.
Findings include
- Acutely swollen dark congested liver (acute death)
- Reddish zonal mottling on a pale and fatty liver (survived a few days)
- Oedema of gall bladder
- Presence of free blood in lower alimentary tract from portal hypertension
- Petechial haemorrhages of the mucosa of duodenum and caecum
- Pale fatty myocardium with extensive subepicardial haemorrhages
- Haemorrhages associated with serious membranes and fatty infiltration of the renal tubular epithelium.
Laboratory results
The main lesion is acute haemorrhagic centrolobular and periacinar necrosis of the liver.
Elevated levels of plasma aspartate transaminase and prolonged prothrombin times are also found.
Treatment Options
Usually dead or dying when found. SCS (Stuffed Cow Syndrome)
Control Options
Green cestrum is difficult to control because the seed can survive for many years. It can also sucker and from underground roots. The plant is long lived.
Control options include
- Stock proof fencing to deny access to cattle
- Mechanical destruction (eg digging out, but will sucker from any roots that are left behind.) Young seedlings are easily pulled out.
- Chemical control - treatment of the cut stump with chemical, or foliar spraying with suitable herbicidese.g.Glyphosphate, Tryclopyr and Picloram, Grazon DS, Garlon 600, Amitrole T, Tordon 75-d (check the labels when and for what purpose it can be used)
- Encouragement of competition with pasture species or planting of native species may be a long term option
(NOTE: The owner of the land has the responsibility of controlling this weed since it is a noxious weed. It is declared as W2 (i.e. must be fully and continuously suppressed and destroyed.)