The Foundation for Arable Research (FAR) is warning growers to be on the lookout for Broomcorn Millet (BCM), an aggressive annual grass which is rapidly establishing itself in many regions, particularly amongst maize and sweetcorn crops.
In some cases BCM can grow up to 2m high, and due to its rapid emergence and strong growth, can present serious management problems as it outgrows most crop types. Growers have only a few days to apply pre-emergence herbicides which will be activated through rainfall, irrigation or incorporation before the weed has emerged from the soil and can no longer be controlled.
Growers can identify BCM by its broad leaf (up to 2cm wide), hairy stem and vigorous growth. When seeding it has large black seeds borne in large bushy panicles which resemble a witch’s broom.
BCM has a large seed (2 x 2.5mm) which germinates readily and grows rapidly. Its large seed size gives it a growth advantage over other grass and many broadleaf weeds. BCM can emerge within three to five days and can set seed within four weeks if stressed. However normally it will take longer to mature and will grow into a large, multi-tillered clump and set thousands of seeds in large, bushy panicles.
BCM is a relatively recent arrival to New Zealand and has had several entry points. It was first found in Northland in 1967 and then later in Otago where it arrived with birdseed. It was first reported in sweetcorn in Gisborne in 1995 and in maize in Hawkes Bay in 1998. It has since spread rapidly through these two cropping areas via cultivation and harvesting equipment. There appears to have been a parallel introduction into the Marlborough district and there is evidence it is established in Manawatu cereal crops. BCM also moves in maize and sweetcorn residues sold as stock feed.
Where to from here?
Broomcorn millet has recently been found in newly grassed paddocks in Hawke’s Bay. If you have BCM on your property, keep watch for it germinating this autumn. This could be an ideal opportunity to reduce the BCM pressure in your field by spraying out the BCM and using the stale seedbed technique for establishing winter grass. If you have already egrassed and the BCM is getting close to having viable seeds, you should consider ways of removing the seedhead (eg mowing, spraying, grazing). Frosts will also take out BCM. Sweetcorn harvesters are cleaning their equipment upon exiting an infested paddock; FAR encourages growers to clean all equipment when exiting paddocks. Growers should also keep a map of known infestations to enable better management and to reduce the possibility of spread. Finally, growers should discuss findings with neighbours and monitor for new incursions.
Andrea Pearson, FAR Maize research Coordinator says, “We don’t have all the answers about this weed yet, however FAR and HortNZ, in collaboration with AgResearch and the MAF Sustainable Farming Fund (MAF SFF) are investigating a number of areas which will hopefully give us the answers we need to help control, and potentially eradicate this weed from our cropping systems.” Grass Weeds of Arable Crops – the ute guide’ is a valuable tool or all growers for use during crop scouting. Thiswill enable more effective weed control for improved profitability. Copies are available from the FAR office.