We know 1080 can kill the possums but is there any harm to our plant species?
Yes however the sodium fluoroacetate molecule is then broken down by the action of soil microbes. Numerous studies into this are referred to by the Department of Conservation's Vertebrate Pesticide Toxicology Manual which states:
Presumably, naturally occurring monofluoroacetate is diluted by rainwater and breaks down in soil after leaves and seeds drop to the ground or when the plants die. Not all micro-organisms can readily defluorinate monofluoroacetate and the rate of metabolism differs with different species of soil bacteria and fungi (King et al. 1994). Sodium monofluoroacetate, the sodium salt of this natural toxin, can certainly be metabolised by some soil micro-organisms, such as Pseudomonas and Fusarium species (Walker & Bong 1981; King et al. 1994). Enzymes capable of defluorinating fluoroacetate have been isolated from several micro-organisms. The active site of the enzyme attacks fluoroacetate. The fluoride carbon bond is cleaved and ultimately enzyme-bound intermediates form non-toxic metabolites such as glycolate (O’Hagan & Harper 1999).
Sodium monofluoroacetate derived from baits will also be dispersed by water since it is highly water soluble and mobile (Parfitt et al. 1995). In older literature, it was suggested that 1080 is retained in solid particles and does not leach. This conclusion was based on the mistaken assumption that 1080 would not be held on cation-exchange sites in soil. However, monofluoroacetate is an anion and New Zealand-based research has demonstrated that it could potentially be leached through soil by water (Parfitt et al. 1995). If heavy rainfall follows the use of 1080 baits, dilution to unmeasurable concentrations (<0.0001 ppm) may precede biodegradation. In comparison to cereal bait, 1080 is retained in carrot baits and will only slowly leach from carrots into the soil (Bowen et al. 1995). However, control operations are planned to coincide with periods of dry weather, and some defluorination by micro-organisms on the decaying baits and in the soil around baits is probable, particularly if the baits become moist. Under favourable conditions, such as 11–20ºC and 8–15% moisture (King et al. 1994), 1080 may be significantly defluorinated in 1–2 weeks. In less favourable conditions breakdown might take several weeks and, in extreme cold and drought, 1080 residues might persist in baits or in the soil for several months.
Sodium monofluoroacetate that has leached into soil may be absorbed by plants (Atzert 1971; Rammell & Fleming 1978). Cabbage (Brassica oleracea capitata) has been shown to systematically accumulate 1080 through its roots, and subsequently become toxic to aphids (Negherbon 1959). To investigate whether herbivores may be at risk of secondary poisoning if they consume plants that have taken up 1080 leached from bait, concentrations of 1080 have been assessed in broadleaf (Griselinia littoralis) and perennial ryegrass (Lolium perenne) following simulated baiting (Ogilvie et al. 1998). The observation in both species that 1080 was absorbed, reached a peak, and then decreased to near the limits of detection, supports previous findings that plants can degrade 1080 (Preuss & Weinstein 1969; Ward & Huskisson 1969). The concentration achieved in broadleaf and ryegrass would be most unlikely to cause poisoning (Ogilvie et al. 1998).
Monofluoroacetate appears to be defluorinated by plants (Preuss & Weinstein 1969; Ward & Huskisson 1972) and animals (Eason et al. 1993a), which may make a small contribution to the removal of monofluoroacetate from the environment following the use of baits containing 1080. (from pages 10 & 11)
To read more from the Vertebrate Pesticide Toxicology Manual please click HERE