Lawn Grub Detection and Control


So you have spent weeks preparing and caring for your lawn, and it is paying off! It has finally become beautifully lush and green, and is like a carpet! A little brown patch appears… you think maybe it just needs a bit of water, or maybe a little bit of fertiliser burn has occurred. No panic, put the sprinkler out for 20 minutes or so and she’ll be right!Over the next few days the brown patch becomes bigger and bigger and is spreading across your lawn! Every green keepers worst nightmare, lawn grub! Now, in Queensland there are a couple of different types worm we commonly refer to as lawn grub, they are White Curl Grub and Army Worm.

white-curl-grubWhite Curl Grub

The first lawn grub is actually scarab beetle larvae which is the juvenile stage of lawn beetle. So really, white curl grub is incorrectly referred to as a ‘lawn grub’ or ‘witchety grub’. These white curl grubs are a serious lawn pest and the signs of infestation are easily confused with other pests, diseases and disorders in turf. The end result of a white curl grub infestation is basically, yellowing to browning and ultimate death. White curl grub will eat away at the root system of turf which in turn causes death, with a serious infestation, you are often able to roll your turf up as the root system is completely destroyed!

Every lawn in Queensland at this precise time will have some white curl grub present and an infestation is generally regarded as a problem when there are 25 of more grubs existing per square meter. If less, a normal and healthy lawn with seasonal growth will sustain any damage caused. However, other external influences may likely exacerbate the problem, such as heat or drought conditions.If you have concerns, the best way to check for lawn grub is to grab a hessian bag or piece of old carpet and lay it on the grass in the late afternoon. Wet the bag or carpet thoroughly and leave overnight. The following morning the lawn grub will have been drawn to the surface, and an assessment can be made.

army-wormArmy Worm

The second lawn pest is known as Army Worm. The adult lawn armyworm takes the form of a greyish-brown moth with a wing span of 35 to 40 mm. Damage from these guys differ slightly from the white curl grub, as they work similar to that of other caterpillars, eating away at the leaves of the turf and damage is often seen as a clear line of dying grass marching across your yard. Often starting closest to the house near external light sources, which attract the adult moth.Determining if you have an Army Worm problem is the same process as above with the white curl grubs. However, be aware that if you have had some reasonable damage occur you will need to be smart with your test placement. Obviously, the grubs will have already moved on from the ‘dead patch’ and will now be working in the green lawn.

Prevention and Treatment

Now if your thinking they won’t get you because you care for your lawn and it is the healthiest in the street… I have news for you! These annoying little guys aren’t interested in your neighbours unsightly mess of a yard. The lawn grub have champagne taste, and won’t settle for the sparkling wine! So unfortunately, the house with the nicest lawn is generally who gets hit the hardest!

Prevention is the key to avoid lawn grub! Unfortunately, most commercially available pesticide are designed to treat an existing problem of lawn grub, rather then prevent it from occurring. Although some of the granular mixes can be present for a little while after application, so will inadvertently prevent… for a short time at least! It’s the old adage, what came first? The chicken or the egg? Well in this case, the moth! The first place to start is ensuring your eaves, house and fences are all free of moth nests. These range is appearance, but mostly look like little cotton-like cocoons. The best attack is with a hose and a broom. This is by no means a guarantee, but at least you are limiting the amount of moths activity around your property.

The most effective treatment for an existing infestation of lawn grub is unfortunately a chemical approach. Chlorpyrifos seems to be one of the most effective treatments and can be found in both a liquid concentrate for spaying and a granular form to be sprinkled and water in. Be extra careful with these forms as they can also be lethal for other animals that may come in contact, including children! The best approach is to treat late afternoon when birds are less active. The birds are attracted the wriggly (and dying) grubs which come to the surface of the lawn after treatment. The most important thing to remember when using ANY chemical type control, is to always read the label and apply at the recommending rates. It is important when treating an infestation to break the lifecycle. Treatment is recommended over a 2 week period – once on the first day, again on day 7 and the again on day 11. This breaks the cycle of cocoon – moth – egg – grub – cocoon… etc.

Treatment is recommended over a 2 week period – once on the first day, again on day 7 and the again on day 11.

As a little bonus for this treatment, the Active Constituent of Chlorpyrifos is often also present in many commercially used products for treating Ant and other insect activity. So while you get the benefit of ridding your beautiful lawn of those pesky grubs, you should also see reduced numbers of Ants, lawn Beetle, African Black Beetles, Cockroaches and Spiders!A natural approach generally relies upon carnivorous birds. There are a number of methods including flooding with water, and also soapy water, which will encourage the lawn grub to the surface, where they will hopefully be picked off by such birds. As you can imagine, this method can yield some rather sketchy results!

Good luck and remember to keep an eye on your Lawn!