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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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Australian Lawn Grubs 3 – African Black Beetles

 

African Black Beetles, Heteronychus Arator, are believed to have originated in Southern Africa. The presence of african black beetles in Australia was first recorded in New South Wales in 1920s. 

Usually found in Australia, african black beetles are also called black lawn beetles because they feed on lawns and grasses. African black beetles are considered as pests for non-legume crops and plants in Western Australia, Eastern Australia, Victoria and Southeast Queensland. There have been reports of attack in grapevines in McLaren and Adelaide Hills in South Australia. 

African black beetles cause significant economic damage to roots of different horticultural crops such as young rooted vines, newly-planted cuttings, olives, potato crops, and other vegetables. African black beetles also attack lawns, newly-sown pastures, young trees, and thin wooded plants. 


Life Cycle 

During spring, adult african black beetles become more active as they feed on stems and plants and lay eggs. Female african black beetles lay their eggs during spring up until the early summer. They wait for three to six weeks for the eggs to hatch into grubs. Grubs are typically white curl, C-shaped and grow up to 25 mm long. African black beetle larvae feed on organic materials and plant roots from late summer until they turn into pupae. Hence, new adults appear from mid-summer to early autumn. 

The adult african black beetle has brown to shiny black color. Its elongated, cylindrical body measures approximately 12 mm long and 5 mm wide. The rear legs are larger than the front legs. The rigid head has large, rounded and compound eyes. Usually found on the land surface or below it, adult african black beetles look like cockchafers that move slowly but have the ability to fly. Flight activities also occur during spring, although there are fewer beetles who get involved. 


Symptoms of Infestation 

The destruction caused by african black beetles normally occurs from mid-summer through winter, to early summer of the next season. New generations of adults emerge during the summer season. They feed on the trunks of young vines on the ground level or just below it. As they continue to attack, they cause wilting and collapse of the vine. Although beetle activity may be low during winter, african black beetles continue to ingest and damage the vines. 

A good indicator that african black beetles are feeding on the vine is the presence of splayed fibrous tissue on its stem. There may not be any signs of beetle feeding that can be seen above the ground until damage has progressed. Vines that have been affected by beetle feeding commonly turn red or yellow. 

Similarly, there could be african black beetles present when the grass dies in patches without any apparent reason. The root system of the lawn gets damaged and the grass looks brown or discolored. Additionally, there may also be the evidence of holes and small mounds of excavated soil due to tunnelling activities of african black beetles. 


Management and Control 

Control of african black beetles is generally difficult. October is normally the critical month for lawns. This is the season when infestation of grubs begins and female beetles start to hatch their eggs. 

Insecticides are often ineffective because adult beetles and their larvae spend much of their time under the ground. However, sprays based on chlorpyriphos or imidacloprid have been found to be an effective means of controlling african black beetles.  

Research has shown that african black beetles survive and reproduce in grassy areas, like ryegrass and paspalum. Therefore, cultivation of soil before planting as well as crop and pasture rotations help reduce the damaging effects of african black beetles. Furthermore, laying plastic mulch over elevated vine rows may control the beetles from crawling to the base of the vines. 

 

 

Australian Lawn Grubs 2 – White Curl Grubs

 

 

 

 

White Curl Grub


lawn grubs such as White Curl Grubs, also known in some places as Cockchafers are the larvae of beetles that feed on the underground stems and roots of plants. These include the Argentine Scarab, Pruinose Scarab, African Black Beetle and some more species native to Australia. The damage they cause may not be too noticeable if the weather is damp and the infestation is not too severe. When the weather is dry, the damage is more likely to show and even lower numbers of these pests will cause worse damage because the plants they are feeding on will already be under stress and not so able to regenerate or withstand an attack. One way to see if your dried out died off lawn does have below ground feeding pests is to see if the grass moves at your touch. A law suffering drought will remain solid but one that has an infestation will slide and shift about where the attack has occurred.


White curl grubs are reasonably well protected by the soil as thy live underground. If you do see them, they can be recognised by the fact that they have three pairs of legs and tend to be shaped like the letter ‘C’. They can grow as long as 2.5cm just before they pupate. The adult beetle is a little smaller being in the region of 1.5cm in length. One way that grubs may be indicated is the behaviour of other animals. If you see meat eating birds such as wood duck, crows and magpies, as well as some other animals like bandicoots. Another method of detection is to put something damp on the grass over night. An old piece of carpet, sacking or something else that will retain moisture. In the morning you will find adult beetles hiding there. There numbers will give an indication of how many eggs have been laid and how serious the problem may be or get. These checks should be done between springtime and summer when egg laying is most likely to be going on.


Eradication.


Having located the pests, we will now move on to getting rid of them. There are some simple measure that may just help. One is to pour some biodegradable soapy water on to the affected area. The lava and beetles are then more likely to rise to the surface where they can be picked off by your garden birds or other grub and bug eating visitors. The beetles are attracted to light, so, turning off outdoor lights when not actually in use may just prevent some of them from coming to your garden.


Another method that is ecologically more sound is to introduce nematodes that are specifically targeted at the insects infecting your grass or crops. These entomopathogenic nematodes usually arrive in a dormant state and have to be moistened so as to reinvigorate them. Be aware though that just adding water will probably not be enough. The mixture will have to be stirred well enough to ensure that they nematodes are distributed equally thought the liquid. Another point to bear in mind is that the area you are going to treat should be doused prior to application. Once again this is to bring the nests closer to the surface so that the nematodes will not have to go so far to find them. One should also put the cure down as it is getting dark because the little helpers may be susceptible to bright sunlight. Once they are applied, the nematodes seek out their hosts and make their way inside through any available orifice. Once inside they disseminate bacteria that create the right conditions for themselves and the nematodes to reproduce until the grub dies. When that happens all the nematodes move away looking for another host to live off.


One can also use chemicals in order to control the numbers of insects. This method is best used on newly hatched grubs because as they get older, their body fat will help them to resist the treatment. Once again you should give the area to be treated a good watering to bring the pests closer to the surface and allow the chemicals easier access to them. Do not forget, if the grubs can not be reached, the cure will not work. Please read and comply  with all warnings and instructions as some of the chemicals authorised for lawn beetles in how lawns can be deadly to humans too. We suggest that you do read all the labels whilst in the store so that you will not buy something that will not suit your purposes, or even worse, do you harm.

 

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Australian Lawn Grubs

 

We’re going to lump the three main things that attack Australian lawns into the category of lawn grubs as that is the name a lot of us know the by. They are all however the offspring of insects. They can sometimes reach plague proportions and completely destroy our lawns or farmers’ crops even though many grasses and cereals can withstand moderate feeding by a reasonable numbers of parasites. We will go through just what they are and how to get rid of them. To start off we will examine Armyworms.


Armyworms.


There are three species of these little blighters although they are all related. These are the Common Armyworm (Leucania Convecta), the Northern Armyworm (Leucania Seperata) and the Sugarcane Armyworm (Lecania Stenographa). The first stage of the lava are only about 1mm long. As they get larger they become more recognisable as they develop stripes along their sides. When it is mature it will get to about 4cms long and have  distinctive stripes along the body with three pale ones on the head and the bit just behind it as well as the tail end. There are no hairs on the smooth bodies. The moth also has a wingspan of about 4cms and is a buff colour. This description will just about fit both Common and Northern varieties with the moth of the Sugarcane species having a dark line on the forewings that are a bit more pale in colour.


The Common Armyworm is native to Australia and found pretty much all over the eastern half of the country. The Northern Armyworm is also found all over the country as well as in New Zealand and South East Asia. The Sugarcane Armyworm has been found in Asia the drier pats of the Australian mainland and sometimes it gets to Tasmania.


The Sugarcane Armyworm is a less of a problem than the others occasionally doing damage to grain crops in Western Australia. The Northern Armyworm tends to cause crop damage in Queensland to plants such as rice, barley, maize, wheat and sorghum. The Common Armyworm will have a go at native grasses in the pastures, perennial grass seed crops as well as wheat, barley and oats.


Life Cycle


All three types are similar and we will describe the Common Armyworm’s life. The adult moths will go to a place they judge to give the best chance of the continuation of their species. They will fly their and lay their eggs on what they consider the best places. This is normally in the cress of cereals or grasses that are drying out or actually dry. The eggs are laid in large clumps by the female numbering up to a thousand at one sitting, being stuck into those folds of the host plant’s leaves. When the lava emerge from their eggs they will use a thin thread of silk to be carried on the wind so as to speed out through the grasses or crops around them. Differences in temperature will control the speed of their hatching and rate of growth. At 20 degrees Celsius they will hatch after about seven days and be read to pupate in another thirty fours days. At thirty degrees these times can be reduced from  two to three days and and thirty four to thirty five respectively. 


Periods of Risk


If you are a cereal farmer, late Winter to Spring is likely to be your worst time. The winter generation can cause quite severe damage to grassland and crops when they gather in large numbers. They will eat virtually everything before moving on to another area. You should be aware that if you sow seed into stubble, the lavae may damage the new growth as it appears. There are usually three generations of Armyworms through the year and it is a good idea to check the bases of plants and under lumps of earth where they hide during the day time. 


Dealing With The Problem


There are a number of different insecticides that can be used to control Armyworms. You must be aware however that these measures are best used when the lavae are a bit smaller, say between one and two centimetres long. If they are bigger than that they are harder to kill and may need quite a bit higher concentration of chemical. As they are more active at night, the best time to spray will be later in the day in order to take advantage of the greater accessibility.


There are also parasites that can help to control Armyworm numbers but these tend to be less effective if there is already a large infestation. This is because they are obviously more slow to act than chemicals. Numbers of Green Carab Beetles will increase quite a lot when there are more Armyworms for them to feed on. Common brown earwigs, shield bugs and some fungal diseases may also help in controlling the pest.

 

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