Evaluation of weed eradication programs: containment and extirpation

Abstract

Weed eradication programs often require 10 years or more to achieve their objective. It is important that progress is evaluated on a regular basis so that programs that are 'on track' can be distinguished from those that are unlikely to succeed. Earlier research has addressed conformity of eradication programs to the delimitation criterion. In this paper evaluation in relation to the containment and extirpation criteria is considered. Because strong evidence of containment failure (i.e. spread from infestations targeted for eradication) is difficult to obtain, it generally will not be practicable to evaluate how effective eradication programs are at containing the target species. However, chronic failure of containment will be reflected in sustained increases in cumulative infested area and thus a failure to delimit a weed invasion. Evaluating the degree of conformity to the delimitation and extirpation criteria is therefore sufficient to give an appraisal of progress towards the eradication objective. A significant step towards eradication occurs when a weed is no longer readily detectable at an infested site, signalling entry to the monitoring phase. This transition will occur more quickly if reproduction is prevented consistently. Where an invasion consists of multiple infestations, the monitoring profile (frequency distribution of time since detection) provides a summary of the overall effectiveness of the eradication program in meeting the extirpation criterion. Eradication is generally claimed when the target species has not been detected for a period equal to or greater than its seed longevity, although there is often considerable uncertainty in estimates of the latter. Recently developed methods, which take into consideration the cost of continued monitoring vs. the potential cost of damage should a weed escape owing to premature cessation of an eradication program, can assist managers to decide when to terminate weed eradication programs.

Priorities in policy and management when existing biodiversity stressors interact with climate-change

“…Management of invasive species that are already established will continue to be essential (McNeely et al 2001;Panetta 2007;Shah 2001). With an expected delay between the time of arrival and time of becoming invasive (Essl et al 2011), research is needed to identify species that have already been introduced, but which have not yet become invasive, particularly garden plants (Marco et al 2010) and pets (Rixon et al 2005).…”

When are eradication campaigns successful? A test of common assumptions

“…The importance of the size of the infestation for eradication success suggests that eradication measures should concentrate on the early phase of the invasion when infestations are still relatively small. This also highlights the importance of delimiting the infestation quickly after its discovery, in order to have a solid basis for decision-making and investing the appropriate efforts in surveillance and control measures (Panetta and Roger 2005;Panetta 2007). As pointed out by Panetta and Lawes (2007), a N=22 N=37 N=17 N=15 N=5 N=43 N=28 N=21 N=6 N=40 N=16 N=21 N=40 N=47 Mean success rate ≥1000 Fig.…”

Managing for biodiversity: impact and action thresholds for invasive plants in natural ecosystems

“…While return times (i.e. intervals between consecutive search and control operations) for extirpation must be sufficiently short to prevent reproductive escape (Panetta 2007), some level of seed production would be allowable under maintenance control. For perennial species, fecundity schedules relative to age and size are of relevance, since plants generally produce the smallest number of seeds during their first reproductive event.…”