AgPest Alert: 1 December 2021

Tasmanian grass grub beetle flights occurring

Region: All NZ

Tasmanian grass grub beetle flights occurring. This pest appears to be spreading and may appear in areas where it has not previously been seen. e.g. It is now present in Cromwell. The significance of this is not yet known. New observations can be reported to colin.ferguson@agresearch.co.nz


Aphids, diamondback moth & white butterfly caterpillars in brassica crops

Regions: Northland, Auckland, Bay of Plenty, Waikato, Gisborne, Hawkes Bay, Taranaki, Manawatu Wanganui, Wellington, Nelson Tasman, Marlborough, Canterbury, West Coast, Otago, Southland

Keep an eye on aphids, diamondback moth caterpillars and white butterfly caterpillars in brassica crops. With warm summer temperatures these can increase quickly. Treating these pests before high numbers occur will provide greatest economic return.


Check sunny slopes for Chilean needle grass

Region: All NZ

Chilean needle grass will become evident in pastures in November-December. Keep an eye out for the reddish purple colour of the seed heads when they first emerge. Each seed has a 7 cm long awn (bristle-like tail). This grass is most likely to be found in pastures on north/west-facing drought-prone slopes but may be present in contaminated stock feed / hay.  If you suspect that you have it, please contact your local council biosecurity people for identification and management advice immediately.


Clover root weevil present in most areas

Regions: Northland, Auckland, Bay of Plenty, Waikato, Gisborne, Hawkes Bay, Taranaki, Manawatu Wanganui, Wellington, Nelson Tasman, Marlborough, Canterbury, West Coast, Otago, Southland

Clover root weevil will be very obvious in most areas. While control is generally not an option careful management of clover will help maintain pasture quality. Additional nitrogen may need to be applied to pastures and clover should not be over grazed.


Apply herbicides to yellow bristle grass before seed heads ripen

Regions: Northland, Auckland, Waikato, BOP, Taranaki

Apply herbicides to yellow bristle grass before seed heads ripen. Avoid moving stock from infested to clean paddocks – seeds can survive in dung.

Don’t make hay from paddocks heavily infested with yellow bristle grass or other summer growing grass weeds – the seeds can survive in hay. In contrast, yellow bristle grass seeds are highly unlikely to survive in well made silage and wrapped baleage.


Note porina flights from now on

Regions: Waikato,  Hawkes Bay, Taranaki, Manawatu Wanganui, Wellington, Nelson Tasman, Marlborough, Canterbury, West Coast, Otago, Southland

Look for and note porina flights as these can indicate when to adopt control measures later if required.


Remain vigilant for velvetleaf in fodder beet 

Region: All NZ

Velvetleaf seed was introduced to NZ as a contaminant of some fodder beet seed and planted in many properties throughout NZ. Therefore, if you have either grown fodder beet or received fodder beet onto your property you need to be vigilant and keep an eye out for this weed and do not let it establish on your property. Velvet leaf is declared Unwanted Organism by MPI and occurrences must be reported and dealt with. For more information phone the MPI hotline 0800 80 99 66 or go to MPI or go to AgPest, or contact your regional council.

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