POISONOUS PLANTS IN NEW ZEALAND

New Zealand Journal of Agriculture, Volume 82, Issue 1, 15 January 1951, Page 46

POISONOUS PLANTS IN NEW ZEALAND

THIS is the fourth section of a series of descriptions of poisonous A pl an t s which grow in New Zealand by H. E. Connor, Botanist, Department of Scientific and Industrial Research, Wellington. Glossaries to be used with the series were published with the first ... , . , ~ r section, which appeared in the October Journal .

DICOTYLEDONS

Hypericaceae

St. John’s Wort. Hypericum perforatum L. (Fig-. 7) Botanical description: Habit-Herb with two-edged, erect stems up to 3ft. tall, arising from underground runners. Leaves— Up to fin. long, sessile, oblong to ovate-oblong,, blunt, with numerous glandular dots. Flowers- yellow, in corymbose cymes. Fruit— Dry capsule. St. John’s wort can be recognised readily by its angled branching arid yellow flowers. (Eurasia and North Africa.) Habitat: Waste places, pastures, and roadsides. Distribution: In scattered localities in both islands; locally abundant in tussock country in South Island. General: Photosensitivity caused by St. John’s wort and other Hypericum species is called hypericism. This disease is more important in Australia than in Europe and the United States of America, and in New Zealand its occurrence makes St. John’s wort an important poisonous plant. Hypericism is reported in New Zealand from Otago, Marlborough, and the Mackenzie country. Sheep, cattle, and occasionally horses are affected by the plant, but only animals with weakly pigmented skins show the symptoms. St. John’s wort is poisonous throughout the year. Drying of the plant does not make it innocuous, and therefore it may be poisonous if eaten with hay in which it is present in large enough proportions. At dipping time photosensitised sheep show symptoms peculiar to hypericism, and as a result of these symptoms sheep are frequently drowned. The sheep struggle violently, somersault in the dip, and drown unless rescued rapidly. A similar condition occurs when animals cross streams or rivers.

Symptoms of poisoning: The early symptoms are oedema of the ears, face, and muzzle and subsequent mummification of the skin. In sheep there is loss of wool down the midline of the pelt and portions of the ears are sloughed. Scabbing and rawness also result from the animals rubbing infected areas. Cattle lick or rub the infected parts of the body.

Poisonous principle: The photosensitising agent is presumed to be hypericin, a red pigment in the plant.

Hypericum spp.

From time to time other species of Hypericum have been suspected of poisoning stock. Tutsan (H. androsaemum L.) was reported as the cause of death in cattle in the Auckland area, but tutsan is generally regarded as non-toxic; feeding trials at the Animal Research Station, Wallaceville, have shown that the plant is non-toxic and

non-photosensitising. Tutsan may be distinguished from St. John’s wort by its shrubby habit; its leaves 2 to 4in. long and more or less heart shaped at the base; and its flowers, which are about lin. in diameter. The native St. John’s wort H. japonic cum Thunb. has been suspected of poisoning sheep on the volcanic plateau. A feeding trial with dried material was negative. No photosensitising pigment is present in the plant. H. • gramineum Forst, f., another native St. John’s wort, is also on the list of suspected photosensitising

plants. It was reported to be lethal to a cow at Lockwood, Auckland. Rose of Sharon or Aaron’s beard (H. caly cinum L.), readily recognisable by its large, bright yellow, solitary flowers, has a very limited distribution in North Island, but has been suspected of stock poisoning. Trailing St. John’s wort (H. humifusum L.), H. acutum Moench., and H. montanum L., though they have not been recorded as poisonous, should be treated as possible photosensitising plants.

Euphorbiaccae Sun Spurge. Euphorbia helioscopia L. (Fig. 8, C and D) Botanical description: Habit Annual herb up to Ift. tall. — Alternate, ovate-cuneate. Flowers— ln umbellately arranged inflorescences with up

Method of Extracting Disease-free Tomato Seed

THE seed-carried virus diseases tobacco mosaic and tomato streak and the bacterial diseases tomato canker and tomato speck are often introduced into tomato crops by infected seed. Recent work has shown that the causal agents of these diseases are carried on the surface of the seed and are destroyed when seed is extracted by the hydrochloric acid method or when infected dry seed is treated with this acid. (The hydrochloric acid method of extraction of tomato seed was described by C. H. Procter on page 480 of the May, 1948, issue of “The New Zealand Journal of Agriculture”.) Tests carried out with fruit from plants infected with tobacco mosaic

and tomato streak have shown that the viruses, which are readily recovered from seed extracted by fermentation or by drying on newspaper, are not present on seed extracted by the acid method. It has also been shown that the organisms which cause tomato canker and tomato speck are killed by this process. . Freedom from these diseases is therefore ensured if tomato seed is saved by the following acid extraction method: — Well-ripened fruit should be selected from plants that are true to type, cropping well, and showing no obvious signs of disease. When pulp has been squeezed from the fruit mix loz. of commercial hydrochloric acid with the pulp from each 51b. of fruit. Extrac-

to 5 forked rays. Fruit Smooth capsule l/sin. long. (Eurasia and Africa.) Habitat: Gardens, waste places, and arable land. Distribution: Common, especially in the North Island. General: In general sun spurge is quite unpalatable to stock, but like other poison plants it may be eaten by stock for unaccountable reasons. No known cases of poisoning by . sun spurge are on record for New Zealand, but poisonings are reported from Canada, Europe, and Australia. A boy is recorded as dying after having eaten sun spurge. Sun spurge should be considered as a plant of possible poisonous capabilities, though the results are not necessarily fatal. This plant may cause dermatitis in susceptible persons. Symptoms of poisoning: Intense gastro-enteritis was produced in a lethal case. Poisonous principle: Euphorbin is considered to be the toxin.

Milkweed. Euphorbia . peplus L. (Fig. 8, A and B) Botanical description: Habit — herb up to 18in. tall, but usually smaller. Leaves— Alternate, stalked, broadly ovate to suborbicular. Flowers — In cymes, bracts ovate, terminating in sharp points. Fruit Capsule lin. long, smooth, with thickened, almost winged keels. (Eurasia and North Africa.) Habitat: Gardens, waste places, and cultivated lands. Distribution: Abundant in both islands. General: Milkweed has been held responsible in New Zealand for the death of a cow and losses among hoggets and lambs, and in Australia for the deaths of and sickness in horses, cows, and sheep. It is rather unpalatable to stock and usually is avoided, but hungry animals may include it with other feed while grazing. Milkweed has been shown to have no deleterious effects on poultry when fed experimentally. It is concluded also from experimental trials that large quantities must be eaten to produce symptoms of poisoning. Symptoms of poisoning: Irritation of the mouth, salivation, gastro-enteritis, and soft faeces which may be bloodstained are the symptoms observed. Poisonous principle: The juice of milkweed is acrid, emetic, and highly purgative.

tion must be done in a wooden or glass container and the mixture stirred frequently (with a wooden stirrer) for 3 hours, after which the seed is washed thoroughly and dried. . Further trials have shown that dried seed, if infected, is rendered free from the diseases by soaking it for 1 hour in a 5 per cent, solution of hydrochloric acid (loz. of acid to 1 pint of water mixed in a wooden or glass container) and then washing it thoroughly. It is advisable to treat all seed of unknown origin by this method to ensure its freedom from disease. —P. R. FRY and A. HASTINGS, Plant Diseases Division, Department of Scientific and Industrial Research.