Pests, diseases and weeds

A range of pests will attack the turf in a home lawn. How severe the attack on your lawn is is highly dependent on the specific pest involved, how healthy or stressed your lawn was before the insect attack, and on the variety of grass you are growing (how good your grass tastes to the pest!).


The weeds that you will generally find present in your lawn will be other grasses, sedges or broad-leaved species. Weeds can also be further classified by the length of their lifespan and are called annuals (their whole lifecycle is complete in one year), biennials (their lifecycle is complete in 2 years) or perennials (a life cycle of many years). It's often hard to tell which type of lifecycle a weed has, but it does impact on the type and success of control procedure to use on them.


While the home lawn may suffer from occasional disease attacks, they are generally not that frequent or severe. In addition, their diagnosis is quite difficult.


Turf Pests

Common pests include armyworm (or other grubs that chew through leaves and stems), mites and scales that injure your turf by sucking the 'sap' from the plant, and nematodes. Nematodes are tiny worms (that you can't see without a microscope) that infect the root system of your turf. The damage they cause makes it difficult for the plant to uptake sufficient water and nutrients to grow very well. 

Often pests attack turf that is growing quickly and is quite lush. Such growth is usually seen after the application of a basic, nitrogen fertiliser that is released quickly into the soil and area around the roots. A good way to encourage more consistent, controlled growth, and to reduce the chances of pest invasion, is to use a slow release fertiliser. 

Chemical re-sellers and businesses that sell pesticides for the home-lawn are a good source of information regarding pesticides for your use. Remember to read the label carefully and to apply it strictly as the label describes.


While some people often think that at least the weeds are patches of green colour within their lawn, you need to be aware that they compete do with the grass species for light, nutrients and water and their presence is often to the detriment of your turf. They are also very soft and collapse under nearly any wear, and can be slippery and dangerous to the people and children using the lawn. 

When controlling weeds, make sure you spray while the weeds are growing actively. The chemicals work by disrupting particular processes within the plant. When the plant is growing actively, the distribution of the chemical throughout the plant occurs efficiently and the cellular processes that the chemical affects are occurring at a high rate. Therefore at this time the best results will be achieved. To further ensure the best results possible, don't mow the weeds you intend to spray from at least 3 or more days before and after herbicide application and don't fertilise in the 2-week (or greater) period before or after the herbicide application. 

As mentioned previously, make sure you minimise the drift from your herbicide spray so that you don't harm other plants in your, or your next-door neighbour's, yard. Also be aware that some chemicals you may want to use to control any weeds in your lawn will also kill your turf, so be particularly careful to apply the herbicide as selectively as possible.


Diseases that affect your lawn can be roughly divided into two categories, those that directly affect and are seen on the leaves of the grass, and those that affect the roots and ground level parts of the grass. 

Foliar diseases come in a range of spots and marks on the foliage. For example, you may have seen tiny orange coloured blobs on grass leaves from time to time. These are indicative of the presence of the rust fungus. Most of these foliar diseases are often 'cured' in the home situation when the grass is next mown and the spots disappear. 

The root diseases are caused by a wide range of fungi and can be difficult to diagnose. Sometimes there are few symptoms that anything is wrong except that perhaps the grass is not growing as vigorously as it should or used to. Because the root system is damaged the plant can't uptake nutrients and water and shoot growth is slowed or stopped. 

In the home situation, the severity of diseases is rarely enough to warrant fungicide applications. Prevention is a better course and includes encouraging steady growth of your turf through the use of slow release fertilisers and ensuring irrigation occurs at times when water won't sit on the leaf surface for long periods. Many fungi require the presence of high moisture and humidity to attack, so irrigating very late in the day or at night when the water can't evaporate can increase the chances of infection, while watering when the leaf surface can dry relatively quickly will decrease chances of infection.

Content included on this page has been modified; original content was published in Lawns and Lawn Care, a homeowner's guide (no date) and on the web by the former Dept of Primary Industries and Fisheries. Permission for use has been granted by the now Dept of Agriculture and Fisheries.