Scarab Beetle.
Sadly, people often class every adult scarab beetle or Curl grub they see as a “bad guy’. This is far from the truth, and every scarab beetle is not necessarily an African Black beetle (ABB) or a cockchafer.
In fact there are only a few that cause damage to turfgrass, so rather than reacing for the spray as soon as you see an adult scarab beetle, the key is to correctly identify them.
ABB is often mistaken for other scarabs, such as the Redheaded, Blackheaded cockchafer, and Yellowheaded cockchafer. This article is an addition to our blog on scarab ID.
After you read this, you will be able to:
- Identify African Black Beetle, Argentine Scarab and Cockchafers.
- Know the lifecycles of African Black Beetle, Argentine Scarab and Cockchafers.
- Know the best cultural and chemical options to African Black Beetle, Argentine Scarab and Cockchafers.
How to Identify Scarab Beetles.
You can tell ABB and Argentine Scarab beetles from cockchafers by:
- How they behave.
- Their biology and
- Their physical attributes.
The main difference between ABB and other scarabs that damage turf grass, is that the adults and the larvae of ABB cause damage. This is in contrast to the Blackheaded, Redheaded cockchafer, and Yellowheaded cockchafers where only the larvae cause any damage.
Therefore, if adult beetles are found and there is stem damage below or just above the soil surface, ABB is a likely a suspect.
African Black Beetle
African black beetle are found in WA, SA, VIC, NSW, and QLD but has has not been recorded in Tasmania.
Historically ABB is a major pest of turfgrass and lawns, and often found in ryegrass, paspalum, and Kikuyu turf.
The climate affects ABB activity, and warm Springs favour activity of this pest, with soil temperatures of 20-25°C being optimal for larval growth. Soil temperatures below 15°C, and high soil moisture both have a negative impact on development1King, P.D.; Mercer, C.F.; Meekings, J.S. 1981c. Ecology of black beetle, Heteronychus arator (Coleoptera: Scarabaeidae) – influence of temperature on feeding, growth, and survival of the larvae. New Zealand Journal of Zoology 8: 113-117..
ABB larvae have a brown head, six legs, and a grey, ‘C-shaped’ body. As the larvae mature the body changes from grey to a cream colour. When they hatch the larvae are around 5 mm long, and they then grow to around 25mm in length. The larvae damage turf and lawns as they prune or completely sever grass roots, and in severe cases the turf can be rolled back like a carpet.
African Black Beetle Life Cycle
ABB has a one year life cycle. In the Spring, adult beetles lay their eggs in the soil, and the larvae then emerge 2-5 weeks later. Their time of emergence depends on the prevailing soil temperature. By around mid January to early March they reach their most damaging stage (third instar).
After pupating in the soil the larvae then emerge as adults, and continue to feed through the Autumn, Winter and Spring. As soon as the adults emerge, they take flight, rather than walk across the ground. It is not known whether these flights are to relatively close areas or are full on migrations. The reason we know this is due to the high numbers caught in light traps compared to pitfall traps that only catch walking beetles.
It is not known what other conditions attract the flying adults to land at a particular spot.
Thanks to Wikipedia, Ian Faithful, from the Department of Environment and Primary Industries, Ecogrow Australia, Cesar Australia and Agriculture Victoria for the images
Argentinian scarab (Cyclocephala signaticollis)
Similar in size and shape to the African Black Beetle, the Argentine Scarab has a mid-tan colour, with subtle striping on the hard outer wing cover. The larvae are up to 25 mm long and have a white to creamy colour.
Scarab Beetle Life Cycle
The Argentinian Scarab has a one year lifecycle, which is 2-4 weeks as eggs, 10-11 months as larvae, 4-5 days as pupae, and 1-4 weeks as adults.
Adults emerge from the pupal stage at the start of Summer, once soil temperatures start to increase. After they mate, females burrow into the soil, and deposit eggs in the upper soil profile in around late December to early January. The eggs hatch 2-4 weeks after this, and larvae begin to feed on turf roots. Within several weeds these larvae reach the 3rd instar. In about May or June the 3rd instar larvae begin to move underground to overwinter in the soil.
Blackheaded Cockchafer.
Blackheaded cockchafers adults lay their eggs between January and February, and have a one year life cycle. Their larvae emerge after 3–4 weeks, and reach the most damaging third instar larval stage in late Autumn and Winter.
The larvae pupate in the Spring and adults then emerge in the mid-late Summer. A good way to differentiate these, is if you handle them they move off pretty quickly (within a minute). This contrasts with Redheaded cockchafers that tend to stay in the classic curl grub “C” shape for several minutes.
Unlike Redheaded cockchafers, Blackheaded cockchafer larvae come to the surface to feed, and are so offer a target to synthetic insecticides like Tempo Xtra.
Redheaded Cockchafer.
Redheaded cockchafer has a two-year life cycle, and it is a pest in its larval stages feeding on roots and organic matter found below the surface. It is common in high rainfall areas (>500mm per annum) of the south-eastern states including the ACT and Canberra2Berg, G., Faithfull, I.G., Powell, K.S., Bruce, R.J., Williams, D.G. and Yen, A.L. (2014), Redheaded pasture cockchafer. Austral Entomology, 53: 144-158. https://doi.org/10.1111/aen.12062.
In their first year, in the late Summer to mid-Autumn, Redheaded cockchafer adults emerge from pupae, but it isn’t until August to October that they emerge from the to take flight and lay eggs.
The eggs hatch in late Spring and the larvae reach the most damaging third instar stage by early Autumn in the second year. Most damage is caused from March to June until Winter temperatures hinder larval activity.
Further feeding damage can occur from late August to December until pupation occurs.
It is a highly destructive pest when population levels exceed 70 /m23Mickan, F. (2008). The Redheaded Pasture Cockchafer, Department of Primary Industries, Melbourne, Victoria, Agnote 1358. . At levels above 700 /m2 it can completely destroy pastures and turf areas4Rath, A.C., & Pearn, S.G. (1993). Development of economic control of the root-feeding cockchafer, Adoryphorus couloni (Coleoptera: Scarabaeidae) with the fungus Metarhizium anisopliae. In: Pests of Pastures. Weed, Invertebrate and Disease Pests of Australian Sheep Pastures (CSIRO Information Services: Melbourne), E.S. Delfosse (Ed.), 332-336. .
Yellowheaded cockchafers.
There are multiple yellowheaded cockchafer species and while their life cycles are largely unknown, they are thought to reach the most damaging third instar larval stage during winter.
How to control Scarab Beetle.
You can control Scarab Beetle and Curl Grub by cultural and chemical means.
Anal opening
All Scarab Beetle larvae have an anal opening at their rear end, which you can see with a hand lens.
With African Black Beetle and redheaded cockchafers, this is a horizontal split. With the larvae of Yellowheaded and Blackheaded cockchafers the anal opening is in a Y shape.
Head capsule
The head capsule of ABB larvae is mostly brown. This is in contrast to the redheaded, yellowheaded and blackheaded cockchafers that have head capsules that correspond to their common names.
Do not use the head capsule colour alone to distinguish ABB from other scarabs. This is due to peoples colour perception varying, and variations in colour between individuals of the same species. As well as differences in colour, the redheaded pasture cockchafer has small pit marks on its head, whereas ABB has a smooth head capsule.
Monitoring and control of Scarab Beetle.
In the not too distant past you had limited options to control curl grubs. Whichever strategy you adopt the first stage is to reduce the risk of damage threshold levels being reached:
Endophyte deterrents
Try and use high endophyte ryegrass varieties like Intense PRG, as these deter Scarab Beetles like African Black Beetle. An endophyte is a fungus that lives in a host plant, and produces alkaloids which deter insets. Fairways and sports grounds dominated by high endophyte grasses have low levels of egg laying by adults. This in turn leads to reductions in larval damage.
Manage soil pH
Aim to keep the soil pH around 6 helps reduce numbers of curl grubs.This does not however, prevent damaging populations from occurring.
Biological Control.
A Research Initiative of the Victorian Golf Association in 2001 shows that Entomopathogenic Nematode (EN) Heterorhabditis spp, give excellent efficacy (100% control) of the EN species on African Black Beetle larvae, and their third instar larvae.
Chemical control of Scarab Beetle.
In the not too distant past there were only a few options avaialable to control curl grubs. Now most turf managers now adopt a preventative approach and spray annually as a standard management practice.
With the majority of the currently registered insecticides, timing is key. Ideally you should to start applications for scarab grubs, when adults are seen as damaging larvae are likely to follow 1-3 weeks in the future.
However, if you don’t do this, then the first stage is to reduce the risk of damage threshold levels being reached.
Thresholds.
Always remember that for if you irrigate your turf you can increase thresholds by 25-30%. Another tip is if birds are digging up the turf then any threshold has been exceeded!
| Pest | Threshold/m2 |
| African Black Beetle | 10 |
| Red headed pasture cockchafer | 70 |
| Black Headed cockchafer | 30 |
Non Chemical Control.
If you apply beneficial nematodes at theright time to kill grubs, these can be pretty effective. You water these into the soil and turf/soil must be kept moist for 48 hours afterward.
Chemical Control.
Preventative.
There are several chemicals that you can use for preventative control, and these should all be part of an effective insecticide resistance strategy. Amongst these are chlorantraniliprole (Acelepryn), imidacloprid (ProForce Recruit 200SC), Scarlet Trio Insecticide and Tetraniliprole (Tetrino Insecticide). Another option to consider the use of Echelon Duo which has the added advantage of being a fertilizer, insecticide and herbicide in one application.
Curative
If you do get a problem with turf damage then you may have to carry out curative control. Imidacloprid (Recruit 200SC) does work on small curl grubs but if they are too big the build up of fatty deposits means you will have limited success. In this case your best option will be Tempo Xtra.
Redheaded Cockchafer.
There are currently no synthetic pesticides registered for use against the Red Headed Cockchafer.
References
Graduated from Newcastle University with an Hons Degree in Soil Science in 1988, Jerry then worked for the Sports Turf Research Institute (STRI) as a turf agronomist before emigrating to Australia in 1993.
He followed this by gaining a Grad Dip in Business Management from UTS. He has worked in a number of management roles for companies as diverse as Samsung Australia, Arthur Yates and Paton Fertilizers.
He has always had a strong affinity with the Australian sports turf industry and as a result he established Gilba Solutions as an independent sports turf consultancy in 1993. Jerry has written over 100 articles and two books on a wide range of topics such as Turf Pesticides and Nutrition which have been published in Australia and overseas.