To quantify soil residual activity and plantback periods for two maize herbicides saflufenacil and topramezone different rates were applied to a cultivated soil and samples (05 cm) collected at regular intervals for glasshouse bioassays Phytotoxic residues of saflufenacil applied at 17 g ai/ha the rate used for conservation tillage and pasture renovation persisted in the soil for lt; 2 weeks for the susceptible species viz white clover onion carrot and radish Residual activity from 102 g ai/ha the rate recommended for maize dissipated within 4 weeks for all species Wheat ryegrass carrot squash onions and tomato were not affected by topramezone residues from rates up to 202 g ai/ha in soil collected 2 weeks after treatment (WAT) However peas white clover and radish all suffered damage in samples collected 2 WAT By 4 WAT only white clover and peas exhibited minor phytotoxicity

Identification of weed seeds from overseas countries can be problematic particularly when diagnostic tools are lacking or incomplete A well trained seed analyst will usually be able to identify seed to generic level but not always to the species level Resources for identification of mature plants are usually more complete Using a seed germination method for intercepted soil samples achieved two goals; it provided an easier route to identification and a measure of viable seed The drawback of this method is the need to grow the plants through to flowering DNA identification is an emerging method for more rapid identification but it relies on availability of matching sequences in an existing database and validation of source plant identification with reliable voucher specimens The limitations and advantages of both techniques are discussed and ways in which timely and accurate identification can be provided for biosecurity practitioners are suggested

Successful management of weed infestations requires an understanding of their biology including seedbank longevity The controlled ageing test used by the Millennium Seed Bank Kew Gardens was evaluated for several grass and broadleaf weed seeds The method aims to estimate seed longevity from a seed survival curve using a controlled environment to accelerate seed ageing Eight species were tested nodding thistle (Carduus nutans) white bryony (Bryonia cretica) batwing passion flower (Passiflora apetala) butterprint (Abutilon theophrasti) thorn apple (Datura stramonium) apple of Peru (Nicandra physalodes) broomcorn millet (Panicum miliaceum) and yellow bristle grass (Setaria pumila) The suggested measure of longevity is the point where germination has fallen by 50 (P50) Seed survival tested here did not follow the ideal logistic model for analysis Because of rapid decline in germination the point where seeds no longer germinate (P0) is considered to be a better measure of seed longevity

The persistence of residual herbicides used in maize (Zea mays) silage crops was investigated in three field trials located in Waikato Taranaki and Canterbury Herbicides used included atrazine and acetochlor applied preemergence and mesotrione and nicosulfuron applied 612 weeks after planting Bioassay of soil samples collected about the time of silage harvest showed small but biologically toxic residues of only nicosulfuron and only at the Taranaki site A subsequent glasshouse study investigated whether the differences in persistence of nicosulfuron were due principally to soil characteristics (four soil types) or rainfall (amount and timing) Heavy rainfall (50 mm) in the first week or two after application or for several consecutive weeks was more effective in leaching the herbicide and reducing the residues than light (10 mm) or moderate (25 mm) rain applied at similar times Also residues of nicosulfuron disappeared faster in soils with low pH and high organic matter

Soil frequently occurs as a contaminant on numerous sea, land and air transport pathways. It can carry unwanted invasive species, is widely recognized as a biosecurity risk, and is usually strictly regulated by biosecurity authorities. However, little is known about relative risk levels between pathways, thus authorities have limited capability to identify and target the riskiest soil pathways for management. We conducted a an experiment to test the hypotheses that biosecurity risks from soil organisms will increase both with declining transport duration and with increasing protection from environmental extremes. Soil was collected from two sites, a native forest remnant and an orchard, and stored on, in and under sea containers, or in cupboards, and assayed after 0, 3, 6 and 12 months for bacteria, fungi, nematodes and seeds.Results showed that viability of Pseudomonas spp., bacteria, nematodes and plants declined over 12 months, irrespective of soil source. Also, mortality of most biota was higher when exposed to sunlight, moisture and desiccation than when protected. However, bacterial and fungal numbers were higher in exposed environments, possibly due to ongoing colonization of exposed soil by airborne propagules. The results were consistent with our observations of organisms in soil intercepted from airports and sea ports, and indicated there is potential to rank risks from transported soils based partly on transport duration and environmental exposure. This would help authorities to optimally allocate management resources according to pathway-specific risks. McNeill et al. / NeoBiota 32: 65-88 (2017) 66 Copyright