Everyday life has become too hectic. We rush out of the house in the morning, wondering where our car keys are, or whether we can get an extension on our project due tomorrow. Until, one day, after another hard day in the office we pull into our driveway and notice that, what was once a gorgeous elm tree, isn’t looking too good. You are scratching your head, not knowing what you did wrong or what can you do to fix it.
There are many reasons why your tree is dying and some may be caused by human negligence. On the other hand, the environment in Australia is marked by extremes of drought, flood, and fire. These factors can affect the ability of a tree to cope with insects or pathogens. Let us now look at some common tree problems.
Common Tree Diseases and Pests Explained
Soil moisture– Keep it moist
When you are choosing which trees you wish to plant, you must be mindful of the climate and pick those which can thrive in Australia, or simply choose trees native to Australia. Golden Wattle is a great choice, especially if you live in the Southeastern Australia.
For the most part, the rain will take care of watering your trees. If you are worried that the soil is too dry you can help with grey water-leftover water after cooking, bathing, and laundry rinsing. Grey water is an excellent source of nutrients, otherwise wasted.
Installing a sprinkler system to water the trees may seem like a good idea, especially if you live in areas where drought is a frequent occurrence, but there is always a danger of over-watering and, thus, killing the tree.
Fertilisation – Even a small amount works
It is important to find a balance when it comes to the use of the fertiliser. Mature trees are generally able to sustain themselves by taking the necessary nutrients directly from the ground. They seldom need the fertiliser. Younger trees, however, can benefit from the use of a small amount of the fertiliser.
You should mulch – Make it your favourite pastime
It is not a tiresome chore, and it will prevent weeds from growing underneath your trees. Mulch should be placed around the tree and how much of it you need depends on the size of your tree. One of the favourite Australian giants, such as Moreton Bay Fig, will need a lot more mulch than a petite garden princess like Lilly Pilly.
Watch Where You Park
It may never cross your mind that parking near a tree could harm it. Especially during those hot summer days when you need the shade for your vehicle. But, as your car sits there, the soil is compressed and becomes much denser, making it hard for the water to penetrate. Also, parking too close to the tree can damage the roots, although it takes at least several years for this to become an issue.
One the most common problems that can cause severe damage to the tree isinsect infestation. Most of the insects that attack trees are native to Australia. Normally, trees can defend themselves against these vicious predators, but if the damage is excessive it can threaten their survival. These insects can be divided into several groups, depending on the type of the damage they cause:
• Leaf defoliators (grazers)
Defoliators include the caterpillars (larvae) of bag and emperor gum moths, and adult eucalyptus leaf beetles. Grazers chew off pieces of leaves and eat them. Damage may appear as irregular shaped leaves or the leaves may be left with holes.
• Leaf skeletonisers
These beetles feed on the surface of the leaves, leaving the veins and the midrib exposed. The leaves remain attached to the tree looking like leaf ‘skeletons’. Major representatives of this group are caterpillars (larvae) of the autumn gum moth and gum leaf skeletonisers. Trees usually are able to survive an attack by this group of bugs, but if they are also suffering damage, such as fire or lack of soil moisture, they may die.
• Sap suckers
The damage from these bugs is easily missed since, initially, there is little or no evidence of infestation. Sap suckers, as the name suggests, suck the sap from the leaves and stems. If you can’t see anything wrong with the leaves, but they are still dying, the cause is probably these sap-sucking insects, such as aphids, psyllids (lerp insects) or scale.
These insects cause damage in the hard tissues of the wood as they tunnel and feed under the bark in living wood. The larvae of longicorn, scarab and jewel beetles, and cossid wood moths are all borers.
Infectious agents that cause plant disease are threatening native flora. Among these the most dangerous is Phytophthora root rot, a water mold (a fungus-like organism). Symptoms of Phytophthora infection are very similar to those brought on by drought, but in the case of Phytophthora attack the soil is warm and moist prior to plant dying.
The other dangerous plant pathogen is Armilarialuteobubalina. It forms a yellowish mushroom in living native plants such as eucalyptus, allocasuarina and acacia species.
Trees often defend themselves against these pesky intruders by forming galls. If the insect lays its eggs inside plant tissues, or the tree is under bacterial or fungal attack, it may form pimple-like growths around the affected area in order to stop it from spreading.
Mistletoe and Dodder-laurel
Mistletoe is a group of semi-parasitic plants, they grow on other plants and use them as source of water and nutrients instead of having their own roots, but, like most other plants with green leaves (and unlike fully parasitic plants), they also produce their own food. A healthy tree can survive a mistletoe attack as long as it is not severe and prolonged.
Dodder-laurel is a group of parasitic, leafless plants native to Australia. They can form tangled mats of stems which can become so dense that they smother their host.
As we have shown, it is easy to avoid the slow decay of your trees, as long as you are careful. There are a few things you can do yourself to help a tree, but in the case of infestation you should consult an expert to save the tree or remove it if required.