AgPest Alert: 17 February 2020

Wanting to control Californian thistle? Mow in the rain.

Region: All NZ

Mowing Californian thistle during rainfall can improve control of this weed by 30% as compared to mowing during dry weather. Best time to do this “wet mowing” is in February/March when the fungi thought to be responsible for this effect are producing spores on the thistle. The effect is likely to be greatest if some members of the thistle population to be mowed are showing signs of disease (wilting, yellowing, dieback).

Watch for Tasmanian grass grub beetle flights.

Region: Gisborne, Hawke’s Bay

Watch for Tasmanian grass grub beetle flights. Beetles are attracted to lights at night. Large numbers of beetles flying may indicate potential damage from the larvae in autumn and winter.

Clover root weevil damage may be obvious but not significant.

Region: All NZ

Clover root weevil adults are abundant and damage to clover leaves will be obvious in most areas. Unless severe this is not significant damage and does not mean the biocontrol agent is absent.

Include non-clover break crop for pasture renewal after Clover root weevil.

Region: All NZ

Clover root weevil: pasture renewal should incorporate a non-clover break crop. This weevil cannot survive in the absence of clover so a clover free break crop provides a temporary weevil free environment that will allow clover seedlings to establish before the weevil reinvades. This will also reduce plant nematodes, plant pathogens and weeds and benefit the new pasture.

Inspect 2-3 year-old pastures for damaging levels of grass grub

Region: Bay of Plenty, Waikato, Gisborne, Hawke’s Bay, Taranaki, Manawatū, Whanganui, Wellington, Nelson, Tasman, Marlborough, Canterbury, West Coast, Otago, Southland.

In grass grub prone areas 2 and 3-year-old pastures should be inspected to determine if potentially damaging levels are present. Early treatment will offer the most protection and maximise returns from the cost of intervention.

Watch for clover flea damage and treat early.

Region: Northland, Auckland, Bay of Plenty, Waikato.

In the North or the North Island, watch for clover flea damage to clover and treat early if required to maximise effectiveness.

Remain vigilant for Velvetleaf

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. Velvetleaf 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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