Navua sedge, a member of the Cyperaceae family, is an aggressive weed of pastures in Fiji, Sri Lanka, the Malay Peninsula, Vanuatu, Samoa, the Solomon Islands, and Tahiti and is now a weed of pastures and roadsides in north Queensland, Australia. Primarily restricted to areas with an annual rainfall exceeding 2,500 mm (98.4 in), Navua sedge is capable of forming dense stands, smothering many tropical pasture species. Seventeen herbicides were field tested at three sites in north Queensland, with glyphosate, halosulfuron, hexazinone, imazapic, imazapyr, or MSMA as the most effective for Navua sedge control. Environmental problems, such as persistence in soil, lack of selectivity, and movement off-site, may occur using some herbicides at the predicted 90% lethal concentration (LC90) control level rates. A seasonality trial using halosulfuron (97.5 g ai ha−1[1.4 oz ac−1]) gave better Navua sedge control (84%) by spraying in March to September than by spraying at other times (50%). In a frequency trial, sequential glyphosate applications (2,160 g ae ha−1) every 2 mo was more effective for continued Navua sedge control (67%) than a single application of glyphosate (36%), although loss of ground cover would occur. In a management trial, single applications of glyphosate (2,160 to 3,570 g ae ha−1) using either a rope wick, ground foliar spraying, or a rotary rope wick gave 59 to 73% control, whereas other treatments (rotary hoe, 3%; slashing, −13%; crushing, −30%) were less effective. In a second management trial, four monthly rotary wick applications were much more effective (98%) than four monthly crushing applications (42%). An effective management plan must include the application of regular herbicide treatments to eliminate Navua sedge seed being added to the soil seed bank. Treatments that result in seed burial, for example, discing, are likely to prolong seed persistence and should be avoided. The sprouting activity of vegetative propagules and root fragmentation also needs to be considered when selecting control options.

Calotrope [Calotropis procera (Aiton) W.T.Aiton] is an exotic shrub or small tree species that is currently invading the tropical savannahs of northern Australia. A chemical trial involving 11 herbicides and four application methods (foliar, basal bark, cut stump and soil applied) was undertaken to identify effective chemicals to control calotrope. Of the foliar herbicides tested, imazapyr provided 100% mortality at the rates applied, and the higher rate of metsulfuron-methyl killed 100% of the treated plants. The herbicides 2,4-D butyl ester, fluroxypyr, triclopyr and triclopyr/picloram killed greater than 80% of the plants when applied by a basal bark or cut stump (when cut 5 cm above ground level) method of application. Plants cut close to ground level (5 cm) were controlled more effectively than plants cut 20 cm above ground level. Chemical control (foliar and cut stump spraying) is a cost effective tool to treat calotrope densities <800 plants/ha. Adoption of pasture management practices that promote perennial grasses, in conjunction with strategic chemical control, would further increase the effectiveness and reduce the costs of controlling vast areas of this weed.

A hand-held burner (Atarus Ranger) was evaluated as a method for controlling woody weeds by flaming in sensitive or riparian areas where traditional methods, such as chemical or mechanical control, have limited usefulness. The equipment was trialled on 3 North Queensland weed species: bellyache bush (Jatropha gossypiifolia), parkinsonia (Parkinsonia aculeata) and rubber vine (Cryptostegia grandiflora), at 5 different heat durations (0, 10, 30, 60 and 120 s) and on 3 plant size classes based on basal diameter (15–25, >25–50 and >50 mm).No significant difference in percentage mortality was recorded between a 10 s treatment and longer heat treatments for bellyache bush and parkinsonia plants, or between a 60 s treatment and longer heat treatments for rubber vine. A 10 s treatment killed 92% of the treated bellyache bush plants and 83% of the parkinsonia plants, while a 60 s treatment killed 76% of the treated rubber vine plants (values are the means of all size classes combined).Flaming was least effective on rubber vine, which had the thickest bark, but was highly effective on bellyache bush, which had the highest bark moisture content. Weeds with a low capacity for root suckering, thin bark, high bark moisture content and low bark density appear the best candidates for flaming. Flaming is an effective technique for the control of woody weeds with efficacy varying among species. Individual plants are targeted, and the technique is accepted by organic farming groups.

The liana, hiptage (Hiptage benghalensis), is currently invading the wet tropics of northern Queensland and remnant bushland in south-eastern Queensland, Australia. Trials using seven herbicides and three application methods (foliar, basal bark, and cut stump) were undertaken at a site in north Queensland (158 700 hiptage plants ha -1 ). The foliar-applied herbicides were only effective in controlling the hiptage seedlings. Of the foliar herbicides trialed, dicamba, fluroxypyr, and triclopyr/picloram controlled >75% of the treated seedlings. On the larger plants, the cut stump applications were more effective than the basal bark treatments. Kills of >95% were obtained when the plants were cut close to ground level (5 cm) and treated with herbicides that were mixed with diesel (fluroxypyr and triclopyr/picloram), with water (glyphosate), or were applied neat (picloram). The costings for the cut stump treatment of a hiptage infestation (85 000 plants ha -1 ), excluding labor, would be $A14 324 ha -1 using picloram and $A5294 ha -1 and $A2676 ha -1 , respectively, using glyphosate and fluroxypyr. Foliar application using dicamba for seedling control would cost $A1830 ha -1 .The costs range from 2-17 cents per plant depending on the treatment. A lack of hiptage seeds below the soil surface, a high germinability (>98%) of the viable seeds, a low viability (0%) of 2 year old, laboratory-stored fruit, and a seedling density of 0.1 seedlings m -2 12 months after a control program indicate that hiptage might have a short-term seed bank. Protracted recolonization from the seed bank would therefore be unlikely after established seed-producing plants have been controlled.

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