Risk assessment on cockspur in Norway
Report no: 2016: 23
Cockspur grass will probably continue to spread in Norway, concludes the Scientific committee for Food Safety in Norway (VKM) in a new risk assessment. The assessment behind this conclusion is that the weed has some non-specific pathways for spread (e.g. relocation of soil) and suitable crops/habitats are widely present in some parts of the country.
VKM has been asked by the Norwegian Food Safety Authority (NFSA) to 1) summarise current knowledge on the occurrence of cockspur grass in Norwegian agriculture, 2) identify pathways for entry and pathways for spread of the weed, 3) assess the potential of further spread and establishment of the weed in Norwegian agriculture, and to 4) assess the potential of harmful effect to Norwegian agriculture. In addition, an identification and evaluation of the effectiveness of risk-reduction measures has been requested.
Cockspur grass in Norway
Cockspur grass has characteristics which make it hard to control effectively. World-wide, cockspur grass is considered to be the third worst weed.
Over the last few decades, cockspur grass (Echinochloa crus-galli), also called barnyard grass, has become a problem weed on arable land in some areas in Norway, particularly in the counties of Vestfold and Østfold. Over all, this area can be regarded as a more or less continuously infested area. The occurrence of cockspur grass also shows signs of spread beyond this area, and establishment of the weed north of the 60 degrees latitude is confirmed.
Pathways for spread
Three pathways are identified as relevant for entry of cockspur grass into Norway. These are bird seeds, ornamental plants rooted in soil, and grass and legume seeds for planting. Four pathways are identified as relevant for spread of cockspur grass within Norway. These are relocation of soil, machinery, seeds for planting, and seeds from places for feeding birds.
The probability of entry of cockspur grass from countries outside of Norway is considered as moderately likely, with a medium level of uncertainty. The overall assessment behind this conclusion is that the weed is frequently associated with pathways for entry (especially bird seeds), the weed survives during transport and storage, and it is not affected by existing pest management procedures applied to consignments that might contain cockspur grass.
Likely to spread
Cockspur grass is already established in parts of Norway. The probability of spread of cockspur grass within Norway is considered as likely, with a low uncertainty. The overall assessment behind this conclusion is that the weed has some non-specific pathways for spread (e.g. relocation of soil), no effective barriers to spread exist, and suitable crops/habitats are widely present in some parts of the country. Climate change may enhance the progress of northward spread.
When it comes to pathways for spread, both relocation of soil and machinery, the two most important pathways, and also seeds for planting, can spread the weed directly to agricultural fields. Therefore, spread within the PRA area might be more likely than establishment from new entries of E. crus-galli.
Cockspur grass is a summer annual plant, and it is hence dependent on arable cropping to survive. All arable land in low altitudes of South Eastern Norway is endangered area due to the high percentage arable farming and the fact that cockspur grass populations have been able to establish from Aust-Agder County in south to Hedmark County in north.
The total area currently infested is roughly estimated to represent less than half of the endangered area. The economic consequences of cockspur grass-infestation of crops are assessed to be major in cereals and potato, and massive in vegetable. The overall assessment behind this conclusion is that in E. crus-galli-infested cereal or potato crops the yield is frequently significantly reduced and additional control measures are frequently necessary, whereas in E. crus-galli-infested vegetable crops, crop production is always or almost always reduced to a very significant extent and additional control measures are always necessary. The uncertainty behind this assessment is high due to insufficient documentation of the harmful effects.
VKM’s Panel on Plant Health was responsible for the risk assessment.