Lawn Grubs

Grub out Lawn Grubs

Archive for January, 2012

Australian Lawngrubs 4 – Argentinian Scarabs


 


Argentine Scarabs, Cyclocephala signaticollis, belong to the group of white curl grubs that feed on the underground stems and roots of plants. Also known as cockchafers in some places, they live underground and cause damage to horticultural crops and turfs after African black beetle. They are most active during the months of April to June. 

It was believed that Argentine scarabs were introduced by a ship from Buenos Aires, Argentina. Native to Uruguay and Argentina, Argentine scarabs were first collected on lawns in New South Wales, Sydney during the late 1940s and has become widespread all over Sydney as far as Canberra and Parramatta in the 1950s. In the past decade, Argentine scarabs have become a serious pest for recreational turfs. 


Life Cycle 

Argentine scarabs generally have a life span of one year. They lay their eggs from early December to late January. The larvae live from early September to early October ant they grow to pre-pupa stage from mid-December to late March or early July to early November. Argentine scarabs reach their pupa stage from early September to late November. 

The adult Argentine scarab looks very similar to an African black beetle in size and shape. However, Argentine scarabs grow from 13 to 15 mm and its vulva is almost 80% of the length of the body. Furthermore, Argentine scarabs have mild tan color with thin, delicate stripes on the wing carapaces and four odontoplates in the stoma. Adult Argentine scarabs are normally seen from late November to early January. 


Field-Grown Crops 

The grubs of Argentine scarabs feed on the roots of lawns and turfs, causing the grass and other plants to weaken and die because of heat or water stress. It can be easily identified when turfs are infested with Argentine scarabs as affected plants wilt and become unstable. The grass on the lawn will soon die even if the soil has high water content; hence, they have to be treated immediately. The number of dying plants will continue to increase as the population of Argentine scarabs also multiplies. 

Argentine scarabs not only damage lawns and turfs. They also burrow into tubers, such as potatoes and kumara, which can then yield a low harvest. 


Detection 

Argentine scarabs feed on the underground stems and roots of the plants. The most destructive stage of Argentine scarabs is the late second instar and the third instar. Adult Argentine scarabs also feed on lawns and turfs although they do not cause as much damage as younger scarabs. 


It is very easy to distinguish a lawn that is swamped with Argentine scarabs. An infested lawn easily slides or rolls up like a carpet where the damage by Argentine scarabs has taken place. Moreover, destruction caused by animal feeding, such as crows, magpies, and wood duck, become obvious. 

It is best advised to leave a wet hessian bag or a piece of carpet on the lawn all night. Collect the adult Argentine scarabs the next morning before it gets hot and dispose of them. 

A pail of water mixed with biodegradable detergent can also be poured into the affected areas of the lawn. This will encourage the larvae and adult ones to move to the surface of the soil where animals can feed on them. 


Control 

Damage can be reduced by using pesticides. Apply the pesticide at dusk, when sunlight will cause the least amount of damage and the soil temperature is between 15-30°C. When using nematodes, thoroughly moisten the area to be treated before applying them and make sure that every square meter is provided with equal amount of nematodes. It is important to wash the nematodes away from the turf into the soil surface after application. 

 


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