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The 1080 Plant Rod Bieleski AHRIH At the moment, there is a lot of interest for fluoroacetate, which is acetic acid and even by the tissues of the animal and a fiery debate about the use of (the material of vinegar) that has had being poisoned. A possum which has 1080 in controlling possums. one of its hydrogen atoms replaced taken in 1080, but insufficient to kill it Interestingly, there are by a fluorine. Acetic acid is an gets rid of almost all the 1080 in its environmentalists on both sides of absolutely key small molecule in the body within a day - about 30% is the debate. The 'antis' argue that 1080 series of steps by which all living excreted, and the rest is broken down poisons our environment, while the things "burn" carbohydrate to carbon to simple fluoride or converted into 'pros' argue that its use greatly dioxide, water and energy. At one of organic fluorides that are no longer reduces possum damage, and allows the steps down the line, acetic acid toxic. In the soil and ground water, recovery of our native vegetation from will eventually become citrate (the 1080 is mainly hydrolysed into fluoride the drastic effects of introduced acid of lemons). It seems that the and glycolic acid, both normal animals. Unfortunately, the debate is main way in which 1080 acts is by materials in the environment. There is being muddied by claims that are not fooling the first few enzymes of the little accumulation in nature because based on any concrete evidence or cycle into thinking it is genuine it is broken down at many levels in even contradicted by well-established acetate. Thus it is processed bio- the food chain. One exception knowledge. Perhaps the biggest chemically until it reaches the stage however is the dead body of the confusion relates to the nature and where it becomes fluorocitrate poisoned possum - there the 1080 use of the bait (the stuff the poison is Unfortunately at that point, the and its toxic derivative fluoroacetate carried in) versus the nature of the enzyme (aconitase) that usually can hang around for up to a month, poison itself. Many of the concerns processes citrate does not handle until the body decays sufficiently for about use of 1080 are essentially fluorocitrate, which jams the enzyme the soil bacteria and fungi to have a about the form of the bait and the so the system is blocked. Energy go. It is this dead body that gives rise way that the bait is distributed, so production drops and citrate piles up, to much of the "by-kill" or secondary that other poisons used in the same in turn interfering with other poisoning, in which non-target animals ways would present the same prob- processes. This is such a crucial effect eat some of its poisoned flesh. The lems. Largely neglected in the public on the metabolism that an organism dog is particularly at risk here, both debate is the nature of the poison with such a blocked system can because it is the most likely to itself, particularly in relation to its rapidly die. The process is like using scavenge, and because it is about 10 status as a natural plant product, a damaged key in a lock. It can be times as sensitive to the poison as a rather than being some unnatural inserted and turned part way round, possum, in terms of the milligrams of creation of unethical chemists. but not only is it unable to open the 1080 per kilogram of body weight To the biochemist, 1080 is an lock, but the lock becomes jammed required to cause death. In intriguing compound. To start with, it so the correct key is unable to be comparison, humans are about half, is very simple, with only 2 carbon used. Because all living things use birds a quarter, and reptiles a atoms out of a total of 8 atoms in the this same biochemical path, all plants hundredth as sensitive. Because of molecule. (In comparison, a simple and animals can potentially be our lower sensitivity and higher body sugar like sucrose has 12 carbons poisoned by 1080 in this way. The weight, the amount that is toxic for a and 45 atoms). Thus it can easily pass very different levels of resistance that human is about 50 times that needed into living cells. All organisms take in occur can come about in several to kill a possum. Although there is a host of different small molecules. ways: the enzyme that starts off with potential for birds and insects living The enzymes in the cell chop, change the acetate can refuse to touch the in the treated areas to be killed, the and join together these small 1080, or the particular aconitase can most careful studies show the kill is molecules until they become part of be unaffected by the fluorocitrate, or very low, to a level where "1080 the structural and metabolic mach- the cells can refuse to let the 1080 in, poisoning is not an additional cause inery crucial to living organisms. or they can break it down into of mortality but simply replaces other Enzymes act in a defined series of harmless products before it can get causes of mortality such as predation steps. An enzyme recognises its into the acetate pathway. and winter starvation" (Spurr, 1994, substrate, modifies it, and passes it Enzymes that break down the 1080 p. 130). In areas like Pukeiti Forest, on to be the substrate of the next are very widespread, being produced the net effect of removing most of the enzymatic step. 1080 is the codename by many soil fungi, many bacteria, possums has been an increase in bird PG 2 The 1080 Plant life, not surprising when you learn that against grazing animals) produced by possums are partial to snacks of bird a number of plant species in at least eggs to go with their vegetable diet. 5 genera within two different plant Does it really matter that we have families, growing widely in two possums in our forests? Too right, different continents. In South Africa, and particularly for those concerned species of 'gifblaar' or 'poison leaf' for conservation of the New Zealand (Dichapetalum; family Dichapetal- flora. There are about 70 million aceae) were known to be highly possums in New Zealand, eating poisonous to stock for a century about 14 million tons of vegetation a before their poison was identified. The year. That's over 2 tonnes per hectare same was true of Western Australian of forest, and about 10% of what all plants like 'box poison' (Gastrolobium our 50 million sheep eat - but then parviflorum) and 'heart-leaf poison' there is over 2 times as much pasture (G. bilobum) (both family as forest. In other words, possums Leguminosae: Papilionoideae) and are grazing our forests about a quarter Acacia georginae (family as intensively as sheep graze our Leguminosae: Mimosoideae). In the fields. Native vegetation, evolved in 1940s chemists twigged that these A poison leaf (Dichapetalum cymosum) the absence of grazing animals, just plants contained heaps of can't withstand that sort of pressure. fluoroacetate - that is, 1080. More But wait, there's more. Possums are recently 'cafezinho' or 'erva-de-rato' the major reservoir of bovine (Palicourea marcgravii; family tuberculosis, a disease that is highly Rubiaceae) in South America has been debilitating to our cows and deer, and found to owe its poisonous properties which also infects humans. It's a to the presence of the 1080 toxin. measure of the health and commercial Some areas of southwestern Australia impact of bovine Tb that MAF currently produce much more 1080 per hectare spends over $5 million per year in than is used for poison drops in our possum control, but estimates the country. To give you an idea just how direct impact on our farming costs to much these plants produce, Heart-leaf poison be $80-100 million a year. The concentrations over 2g/kg dry leaf (Gastrolobium bilobum) challenge is to not only reduce the have been found - meaning that just possum populations, but to do so 4kg of leaf would be enough to of what is a natural occurrence. Thus before the health problem extends provide baits for treating 1 hectare of the risks of putting synthetic 1080 beyond the 25% of the country where forest, and 2-3g (the amount of tea in into the environment have to be read bovine Tb is now present. And a tea-bag) has as much 1080 as a in that light. reducing possum numbers does work. standard bait used in air drops, easily In parklands where an effective enough to kill a possum. For those Reference poisoning or trapping campaign has who believe in using only organic Spurr EB (1994). Review of the been carried out, there have invariably products in our horticulture, impacts on non-target species been rapid and easily-visible Gastrolobium parviflorum extract of sodium monofluoroacetate improvements in the vigour of the should be a highly acceptable material (1080) in baits used for brushtail trees. We can see this for ourselves for possum control! A much wider possum control in New on Rangitoto and in the Auckland range of plants, including soybeans Zealand. Proceedings of the Regional Council parks. In the and tea, produce low concentrations Science Workshop on 1080, Waitakeres this year, I saw rata of 1080 under some circumstances, pp124-133. Royal Society of flowering for the first time in a couple mainly when growing on fluoride-rich New Zealand, Miscellaneous of decades, while bird lovers tell us soils.

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