Positive Pasture Walks
The Pasture Walks hosted by GLENRAC last week at Pinkett and Bald Nob have received positive feedback from farmers attending. The events were a new format for GLENRAC lasting only one and a half hours on-farm and hands on, in the paddock. The Pasture Walks were attended by 37 farmers.
The Pasture Walks were hosted by local farming families Neville & Val Duddy and Peter & Julie Donnelly at Pinkett and Bald Nob respectively. The events were held in response to enquiry from farmers on the affects of the pasture insect pests causing significant damage in pastures this season.
Technical expertise for the event was provided by Mick Duncan and Jeff Lowien, both agronomists with an extensive history of providing advice to Northern Tablelands graziers.
The increased activity of the cockchafer larvae this season is largely the result of favourable conditions in the preceding summer season when the adult scarab beetle was laying eggs in tall standing pastures. Pastures most affected are typically shallow rooted grass species such as sub clover, ryegrasses and cocksfoot. The larvae found at both sites were determined to be either the red or yellow headed pasture cockchafer.
The adult scarab beetles include the Christmas beetles, are present from November to March. These beetles live for 1 to 9 weeks and each female may lay 20 to 40 eggs. There are 3 larval stages which are commonly referred to as white or curl grubs. The most damage occurs in the 2nd or 3rd stages when the larvae feed on plant roots, effectively cutting off plant roots. The damage to plant roots also makes the pastures easy for birds, such as ibis, to uproot the plants when they are foraging for the grubs. Bare areas created further encourage the growth of opportunistic species such as sorrel, thistles, cudweed and fleabane.
There is no commercially available means of controlling the cockchafer grubs in pastures. Instead options for managing pastures affected were discussed at the pasture walks. Strategies suggested include broadcasting seed on affected areas to promote regermination in the growing season, if severe enough to warrant replanting consider with a non-grass crop for the first season. The larvae do not like to be physically disturbed so cultivating paddocks is also an option.
Mick Duncan concluded at each pasture walk with the statement ‘that the cockchafer is naturally controlled by its predator population which includes birds, a parasitic wasp, fungi, bacteria and protozoa, over time the predator population increases to effectively control numbers.”
Mick Duncan also mentioned the importance of farm biodiversity, with one of the known insect predators, a parasitic wasp that attacks the larvae, known to live in the native blackthorn (Bursaria spp.). Farmers can promote habitat for natural control agents by providing suitable nesting and roosting sites for birds and promoting nectar bearing native plants (including eucalypts, tea-trees, rough barked apple and blackthorn) near or in pastures as sources of food for insects.
A comprehensive fact sheet can be found on the NSW DPI website (www.dpi.nsw.gov.au/primefacts) titled Primefact 512 “Scarab grubs in northern tableland pastures”.
GLENRAC thanks our Pasture Walk hosts and Northern Tablelands Local Land Services for their support in presenting this event.