Yellowheaded and redheaded Cockchafer in pastures and crops
There is not a lot of research done on this pasture pest in Central Tablelands area. However, we do know it did impact perennial pastures and crops in the 2013 season. Therefore, given its 2 year life cycle and the favorable dry late winter & Spring last year, it could potentially cause severe production losses in the long term.
It is typically a problem for shallow and weak rooted plants such as Barley grass, Ryegrass and Sub-clover. Whereas, deep rooted plants such as Oats, Lucerne, Fescue, Phalaris and Cocksfoot are known to be more resilient to larval damage.
Did you have a problem with Redheaded Cockchafer in 2013?
Anecdotal evidence suggests that the Redheaded Cockchafer is more likely to lay eggs in long grass in late Spring. Therefore if you had a problem with Cockchafer damage in 2013, it may be worthwhile to check the paddocks that had high biomass in the late spring of 2013 for signs of Cockchafer grubs.
The redheaded cockchafer (Adoryphorus couloni) and the blackheaded pasture cockchafer (Acrossidius tasmaniae) have darker head capsules, which are easily confused with the yellowheaded cockchafer. The blackheaded cockchafer moves above the soil surface to feed at night, whereas the redheaded and the yellowheaded cockchafer (Sericesthis harti, Sericesthis spp.) grubs stay beneath the soil where they feed on decaying organic matter and live plant roots. It is important to know which species you have in your paddock, because the blackheaded cockchafer is the only one that can be cost effectively controlled by a pesticide.
June is the best time to sample for Yellowheaded Cockchafer grubs in your paddock. All you need is a spade to dig the soil 10-20cm deep, ten to twenty times across a paddock. If you count four larvae per spade square then this is roughly equivalent to 100 larvae per m2. Even 30 larvae per m2, will have a severe impact on biomass if it is a susceptible crop or pasture species.
Forward planning is the best tool against these pasture grubs. Winter crops sown after years of pasture are the most vulnerable.
Increasing grazing intensity in spring, summer and autumn will expose the eggs and larvae in the topsoil. This will make them more susceptible to desiccation and predation by birds. Fallows that are prepared in Spring for early sown Oats or even a Summer Millet crop, will help to reduce the impact of this pasture pest on the subsequent crops and pastures sown in susceptible areas.
Cultivation reduces pasture grub populations, but minimum or zero till may best suit your system and soil type.
If you'd like a pasture grub identified, please call either Phil Cranney or Clare Edwards. Sending photos via text or email, is always a great way to help us identify a potential pasture pest.
Phil Cranney, Pastures Officer | Phone: 6363 7888 | Email: email@example.com
Clare Edwards, Pastures Officer | Phone: 63781709 | Email: firstname.lastname@example.org