Landscape diversity and field margin management
Australian vegetable production is under increased pressure to achieve more profitable and sustainable production as input costs are increasing together with increasing vegetable production (2% per annum), the Australian population (1.7% over the same period, Australian vegetable industry Strategic Investment Plan 2012 – 2017) and environmental degradation. Thus, an integrated approach that achieves reduced inputs and sustains natural habitats as refuges and a resource base for beneficial organisms is required. The homogenous nature of agricultural landscapes reduces biodiversity of natural enemies and thereby biocontrol, but this can be partly offset by developing refuges at field margins and in the surrounding landscapes as shown in a large body of international research. In this project, we review Australian and international literature related to the role of field margins and landscapes surrounding crop fields in providing resources to beneficial organisms and reducing arthropod pest pressure in vegetable and other crops. Using literature on bio-physical data, together with published literature on farmers’ perceptions and adoptions, as well as expert (researcher) opinions from conducting interviews, we captured the current knowledge, identified knowledge gaps, and farmers’ perceptions and barriers to adoption. These results were used to generate recommendations on how to manage off-production habitats at field margins and in surrounding landscapes for vegetable pest suppression, and what is needed for this to be implemented by farmers. Several trends are emerging that show support for on-farm and area-wide vegetation management that will contribute to pest reduction, yet knowledge gaps need to be filled before we can implement on-farm region specific management actions for the vegetable industry. The general emerging trends include: Weeds generally support pest abundances and their reproduction; Native plant species generally support beneficials and do not support pests (with some exceptions), and there are options for native plants that can provide additional on-farm income (see Revegetation by Design); Lucerne can provide multiple benefits and low risk, such as high abundance of beneficials, low pests problems, and additional farm income; Beneficial arthropods need a certain habitat area and configuration in landscapes surrounding crop fields, but which habitat, how much and where remains to be investigated in Australia. It appears that >10% lucerne in a circular landscape of 1.5km diameter provides benefits in terms of biocontrol in vegetable crops. Adjacent woody vegetation (shelterbelts, remnant woodland) provides multiple benefits, including in-field biocontrol, and even narrow patches (25 m x 100 m) have been shown to support beneficials, that then move to the adjacent crop. However, the required amount at the landscape scale remains unknown; and Habitat condition such as complexity (plant diversity and structure including under- mid- and upperstory) and weediness (exotic grasses and broadleafs) should be taken into account and managed.