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Bracken (Pteridium) holds a pivotal role in succession, usually occurring in sequence between plagio-climax communities such as heathland and woodland. It is at this interface that bracken causes problems for man, as the sub-seral communities are more valuable for agricultural use and most have a greater conservation value than bracken-dominated ones (there are a few exceptions). This paper examines the role of bracken in a series of successional trajectories on lowland heaths; there is evidence that bracken occurs in a trajectory towards birch woodland in Dorset. Whether the bracken stage is an intermediate stage towards woodland or acts as a ‘mini-climax’ in itself remains to be demonstrated. Thereafter, the impact of bracken control on vegetation development is examined from two successional viewpoints, succession reversal towards the early successional communities, and successional accelerations towards woodland. A range of examples is provided from: (1) lowland heaths in England; (2) moorlands in upland Britain where bracken has been treated with asulam; and (3) in North Wales where attempts have been made to restock woodlands.

We measured the cholinesterase activity inhibition to determine concentrations of asulam and fenitrothion in soil, surface runoff and subsurface drainage, following simulated rainfall applied 1, 7 and 19 days after application of the pesticides to sloping pasture plots with downslope buffer strips. In the soil and surface runoff, both asulam and fenitrothion levels dropped below detection limits by day 19; in subsurface drainage, neither pesticide was detected at any stage. Whilst the reductions in pesticide concentrations in surface runoff with respect to applied concentrations were considerable, we cannot be certain that this was due to the action of the buffer strips.

Treatment of porina (Wiseana spp.) (Lepidoptera: Hepialidae) eggs with copper oxychloride enhanced the viability of the eggs in laboratory cultures. A commercially available wettable powder fungicidal formulation of copper oxychloride was more effective than formalin, asulam, captan, chlorthal-dimethyl, or maldison.

(1) The effects of separate and simultaneous grazing by Gastrophysa viridula Degeer and herbicide treatment (asulam) on Rumex obtusifolius L. and the influence of asulam on G. viridula were investigated. (2) Asulam had little influence on the survival or rate of development of G. viridula when used as a contact agent on eggs, first-instar larvae and adults. (3) The ingestion of asulam-contaminated leaves reduced the fecundity of female beetles by 64% and the rate of development of the whole generation by 4 days. (4) The presence of asulam in R. obtusifolius leaves had no significant influence on the oviposition and feeding site selection of gravid beetles. (5) In the field, there were fewer second generation G. viridula on asulam-treated plants than on untreated plants; the total, shoot and root dry weights of asulam-treated plants were significantly lower than those of untreated plants. Grazing significantly reduced the dry weight of asulam-free plants but did not further reduce the dry weight of asulamtreated plants. (6) Plant survival was unaffected by grazing or low herbicide levels. Approximately 60% of plants survived treatment with high levels of asulam. (7) The stage of beetle development when the host plants were sprayed was important for the continued survival of G. viridula. (8) It is suggested that the density of beetles and the time of their release in relation to the spraying date of dock with asulam may be manipulated to improve the efficiency of any dock control programme.

Seven chemicals were evaluated for selective control of doublegee (Emex australis) in legume pasture in 14 field trials conducted at several sites in Western Australia over three years. The effect of removing doublegee on pasture growth was studied in four field trials over the same period. Three hundred and fifty to 700 g a.i. methabenzthiazuron ha-1 gave good selective control of this weed except at Chapman and Wongan Hills in 1974 where the beginning of the growing season was poorly defined. The selectivity of bromoxynil and WL 6361 1 in one year of trials was similar to methabenzthiazuron but that of asulam and metoxuron was too restricted for practical use when doublegees were sprayed at the 2-4 leaf growth stage, 2,4-DB showed selectivity on doublegees with 12 leaves, and no herbicides were satisfactory on doublegees with more than 12 leaves at the time of spraying. Pasture growth and clover seed production was not substantially increased by controlling doublegee.

The incidence of fireweed (Senecio lautus) in carpet grass (axonopus affinis) dominant pastures was studied in two cutting experiments and a grazing trial at the Agricultural Research Centre, Wollongbar. Experiments were conducted on pastures initially dominated by carpet grass. Lower fireweed density resulted from higher herbage production or changes in botanical composition from carpet grass to the more competitive paspalum (Paspalum dilatatum) and kikuyu grass (Pennisetum clandestinum). These changes were rapidly achieved by the application of nitrogen fertilizer. Super phosphate application and management for clover development favoured invasion by fireweed in the initial stage. Subsequently the effect of superphosphate was similar to that of nitrogen fertilizer due to the response of more productive grasses to nitrogen fixed by clover. Under grazing, the density of fireweed was increased by high stocking rates, but was reduced markedly by a change to kikuyu grass dominance even under heavy grazing. Fireweed density was negatively related to per cent kikuyu grass. The densities of fireweed measured were not high and classification of fireweed as an undesirable species in these pastures is questioned. This conclusion may not apply to areas improved with temperate pasture species or in cultivations.