Lawn Grubs

Grub out Lawn Grubs

Archive for February, 2011

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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Know Your Enemy

 

lawn grubs can significantly damage your lawn, and you may not notice significant damage until infestation is well underway. 

Lawn grubs are generally white, and their bodies have a typical “C” shape to them. Grubs are larvae, and if left to mature, will eventually turn into beetles. The most common type of grub is the white grub, with the adult becoming a “chafer” beetle, tan in color. Another common type of grub is the May/June beetle. What’s notable about these two types of common grubs is that while the chafer beetle has a lifecycle of just one year, the May/June beetle has a cycle of three years.

 

Where they hatch and feed 

Grubs generally hatch on lawns that have been well watered, with eggs being laid on the soil in mid summer. The eggs will hatch and damage will occur beginning late midsummer, and may occur right up until early fall season.

 

Monitoring progress

 European chafer beetle has a lifecycle of just one year, while the June beetle has a three-year lifecycle. This may change how you want to manage them.

 

Noting damage

You’ll first note lawn grub damage by noticing that the grass will turn brown. It can be difficult to determine that this is actually lawn grub damage at first, because it looks much like many other things that can also occur at the same time of the year, such as short-term drought or drying of the soil.

 

Taking note of grubs’ stages of growth 

When first hatched, both June and chafer beetles are about 3 mm long, and can grow to sizes of between 2 and 4 cm at full larval stage growth. Beginning about late May or early June for June beetles and June to mid July for European chafer beetles, the beetles will begin to lay their eggs. By mid-June, May or June beetles’ eggs have hatched, and the larva will begin to feed on organic material. This is also true of the European chafer beetles’ larvae.

 

This is where the differences begin to occur between the European chafer and June beetles, though. With the June beetle larvae, the larvae move below the frost line to spend the winter and then reemerge in the spring when warmer temperatures arrive. Upon reemerging, they continue to feed. The same thing happens in the second year, with larvae moving below frost line when cooler temperatures arrive. They pupate in their third year, in June, after they have fed for a short time upon reemerging in the spring.

 

It’s important to note that with the June beetle larvae especially, it’s entirely possible to have larvae at different stages of growth below your frost line at any given time; that means that when you treat this particular infestation, you have to make sure that all stages of larval and adult growth are treated.

 

With the European chafer beetle, it takes one year for the beetle to complete its lifecycle, meaning that it goes through all stages in one year. The larvae hatch as long as there’s moisture present in the root zone, and can stay feeding until November or December. They move below the frost line, and then go back to grass roots and began feeding in early spring; they pupate in May.

 

Treating for lawn grubs 

Sample for infestation in areas you suspect it’s occurring in late fall, and treat then. It would be most effective then, as opposed to spring or early summer treatment. Formulations for insecticide treatments change all the time as new products come out, so check to see which are the most effective on the market at the time of treatment.

 

 

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