AgPest Alert: 1 April 2021

Inspect young pastures for grass grub and porina.

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

In grass grub or porina prone areas check pastures for damage. Grass grub damage is indicated initially by loss of clover and subsequently by patches of pasture turning yellow and later becoming soft under foot. Porina damage initially appears as small (approx 5 cm dia.) areas of bare ground. Both pests should be controlled as early as possible to maximise returns and protect long term pasture production and quality. Although heavy rolling or high stocking rates may provide some level of grass grub control, conventional insecticide (diazinon) may be the only recourse. It is now generally too late to obtain good control of porina using diflubenzuron, although caterpillars from late February/March flights in the North Island are still susceptible. In most cases porina control now needs to be by conventional insecticide.

Direct drilling new pasture?

Region: All NZ

If pasture establishment by direct drilling is going to be used check those pastures for slugs and grass grub as even low numbers can devastate young seedlings of pasture or crop plants. Wet sacks can be laid in the paddock, slugs will shelter under these and be seen on the pasture surface if inspected after 2-3 days – more than 2 slugs per sack could result in seedling loss. To detect grass grub dig at least 10 15 x15 cm holes 15 cm deep and search the soil – as few as 1 grub/hole could cause damage.
Small weeds can be effectively controlled with herbicides which are soft on clovers but if the weeds get too large they can only be controlled with herbicides which also damage clovers.

Damage from black beetle larvae showing.

Region: Northland, Auckland, BoP, Waikato

In the northern North Island damage from black beetle larvae may be showing. Unfortunately little can be done to prevent this. Adults are deterred by some endophyte- infected grasses which will reduce egg laying and larval numbers. See DairyNZ Pasture Renewal Guide.

Northern North Island watch for clover flea damage to clover.

Region: Northland, Auckland, BoP, Waikato

In Northland, South Auckland, Waikato and the Bay of Plenty watch for clover flea damage to clover and treat early if required to maximise effectiveness. See NZNovachem Agrichemical Manual.

Tasmanian grass grub damage may be showing.

Region: Gisborne, Hawkes Bay, Canterbury, Central Otago

In areas where Tasmanian grass grub can be a problem damage may be seen. Check pastures particularly around stock camps and assess numbers to determine if insecticidal control is warranted.

Velvetleaf and other weeds will be well into flowering now.

Region: All NZ

Velvetleaf and other weeds will be well into flowering now. If you notice a new weed get it identified. Any new plants that are appearing on your property or in your crops should be identified to a) assist you in managing it in the future, and b) to check that it is not a new incursion that should be dealt with on a wider scale. Send a clear photo(s) to AgPest to have it identified.

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