Biological spectrum of weed flora and vegetation of raspberry plantings in Serbia

Issues with regard to weed bioagents in raspberry plantings have been of minor public concern so far. Although the problem should not be neglected, to date there have been scarce literature data. Due to a substantially high population density and broad habitus, weeds tend to compete for the above- and below- ground space including natural resources such as water, nutrients and light. The specific surrounding weed microclimatic conditions favour pathogen and pest development. Besides, weeds are often primary or secondary hosts to plant disease and pest pathogens and thus their contribution to the presence of harmful bioagents in raspberry plantings is significant. Timely weed control and management is of key importance for the employment of conventional raspberry cultural practices and harvest. A timely and proper weed imposes the need to identify the floristic composition and biology of weed community in raspberry plantings. A survey was conducted in more than 40 raspberry plantings (southwestern part of Serbia) and about 85 weed species were registered in 5-to 15 year old raspberry plantings where both intensive and semi-intensive productions have been employed. The predominating grass weed species according to density were Panicum crus-galli, Setaria glauca, Digitaria sanguinalis and Setaria viridis, and broadleaf species: Amaranthus retroflexus, A. hybridus, Chenopodium polyspermum, Erigeron canadensis, Galinsoga parviflora, Glechoma hederacea, Polygonum lapathifolium, Convolvulus arvensis, Calystegia sepium, Rubus caesius etc. The flora life spectrum analysis showed the presence of terophyta, 52%. However, the analysis of the vegetation life spectrum (considering the quantitative presence of each species for the given life form) show the importance of the presence of perennial species such as hemicryptophytes and geophytes, partly herbaceus chamaephytes and phanerophytes for the structure of the biological spectrum of the community (65%). This is of major importance for the proper decision on wedd control measures. Thus, attention should be focused on intensive growing system during the entire vegetation period (following raspberry harvest) and on the use of persistent broad spectrum herbicides. Therefore weed control practices should focus on predominating grass weeds and perennial broad leaf species such as: Calystegia sepium, Convolvulus arvensis, Cirsium arvense, Rubus caesius, rumex crispus etc. The presence of Phragmites communis and Lythrum salicaria was significant which threatened to penetrate the fields from the edges of the raspberry plantings. Both mechanical and chemical control measures should be taken into account due to significant vegetative and generative potential of these weed species. Weed management in orchards requires herbicide application in rows and interrows are either shallow ploughed or left to natural grass coverage (regular cutting needed). The choice of herbicides needs to coincide with the floristic composition of the weed community in raspberry plantings, whereby special attention should be paid to troublesome perennial weed species.