Experiments conducted from 1977 to 1979, at Rutherglen, north-eastern Victoria, investigated seed production, seed longevity, seasonal emergence and phenological development in wild radish (Raphanus raphanistrum L.), a weed of field crops. Seed production of wild radish reached 17 275 seeds/m2; seeds retained viability and germinated over a period of three years. The loss of viability was faster at the soil surface or at 1 cm depth than at 5 or 10 cm. Of 1000 wild radish seeds buried at 1 cm depth, 737 emerged after three years, compared with 367, 167 and 5 at 0.5 and 10 cm, respectively. Phenological development of wild radish was affected by time of planting, and the duration of the period from plant emergence to plant senescence ranged from 5 to 10 months. Temperature appeared to influence development up to flowering, but photoperiod affected the length of flowering. Plants emerging at any time during the year were able to flower and seed successfully. The implications of these findings for control programs are discussed.

The effect of different cultivation and sowing methods on wild radish (Raphanus raphanistrum L.) density in 4 successive wheat crops was measured in an experiment in north-eastern Victoria. The number of seasons taken for populations to decline below an estimated threshold for economic spraying of wild radish (5-10 plants/m2) was examined. Two herbicide applications in each crop in all but one treatment prevented or significantly reduced wild radish seed production during the experiment. Wheat sown after mouldboard ploughing (MBP) in the first season contained wild radish at 42 plants/m2, before spraying. Densities were significantly higher (P<0.05) when wheat was direct drilled (96 plants/m2), or sown after cultivation to 80 mm (116 plants/m2) or to 50 mm (202 plants/m2). MBP in the first season followed by cultivation to 80 mm or direct drilling in subsequent seasons resulted in wild radish populations below the threshold for economic spraying in the second crop. Cultivation to 80 mm before sowing in the first 2 years, followed by direct drilling in subsequent years resulted in a wild radish population of 6.9 plants/m2 in the third crop. This density was within the range estimated as the threshold for economic spraying. Wild radish densities on treatments cultivated to 50 or 80 mm before sowing, or direct drilled each year, had declined to within or below the threshold for economic spraying by the fourth crop.

Summary. The persistence of trifluralin was investigated at 3 sites in southern Australia over 8 years. Persistence varied from year-to-year, with the highest persistence being recorded at all sites in the dry year of 1984. Trifluralin persistence (expressed as a percentage of the initial measured concentration) 1 year after application was lowest at Rutherglen (7–22%), followed by Dooen (7–26%) and Walpeup (13–120%). Trifluralin degradation at Walpeup in 1984 was negligible. The resultant high residue concentrations would have posed a threat to subsequent crops. However, 1 year later after the subsequent fallow, the residue concentration had dropped to more typical levels. Trifluralin did not accumulate after repeated application (either 1 or 2 years apart) at all 3 sites. It was found important to measure the amount of trifluralin in the soil immediately after application because the trifluralin concentration could not be assumed from the rate. Soil concentrations immediately after application ranged from 32 to 138% of that expected from the nominal application rate. Therefore, measuring initial concentrations when comparisons were to be made between treatments, years and sites, was essential. In addition to studies of 1 year persistence, trifluralin concentration was also measured 2 years after application at Walpeup and Dooen. There was evidence to suggest that the rate of degradation over the same 1 year period, was different for a recent application when compared with weathered trifluralin residues from a previous application. Correlations between persistence and various weather factors indicated that the most influential factors were those that occurred in the first 60 days after application. These included total rainfall, effective rainfall (rainfall minus evaporation) and average maximum temperature.

The relative effectiveness of herbicides from the aryloxyphenoxypropionate (fop) and cyclohexanedione (dim) chemical families for the control of volunteer wheat (Triticum aestivum L.), oats (Avena sativa), triticale (Triticum x Secale) and annual ryegrass (Lolium rigidum Gaud.) in narrow-leafed lupins (Lupinus angustifolius) were evaluated over a 3-year period near Rutherglen in north-eastern Victoria. Herbicides tested included diclofop-methyl, fluazifop-pethyl, haloxyfop, propaquizafop, quizalofop-p-ethyl, clethodim, cycloxydim, sethoxydim, and mixes of fluazifop-p-ethyl + diclofop-methyl, and fluazifop-pethyl + sethoxydim. Effective grass control needed to prevent disease carryover is defined as greater than 98%. Haloxyfop at 78 g a.i./ha and clethodim at 120 g a.i./ha consistently gave greater than 98% control of all target species. Quizalofop-p-ethyl at 12 g a.i./ha gave greater than 98% control of volunteer cereals but annual ryegrass control ranged from 83.7 to 44.1%. Cycloxydim at 100 g a.i./ha produced similar oat and ryegrass control to that of 563 g a.i./ha diclofop-methyl. Sethoxydim at 93 g a.i./ha, gave significantly (P < 0.05) better control of annual ryegrass than the recommended rates of diclofop-methyl, fluazifop-p-ethyl and propaquizafop. The addition of 47 g a.i./ha sethoxydim to 32 g a.i./ha fluazifop-p-ethyl significantly improved ryegrass control than low rates of fluazifop-p-ethyl alone.