Parasites are not all bad

Mention the word parasites and all manner of nasties spring to mind. But we have a few parasites in the bushland that won’t harm us and are part of the natural landscape.

Parasitic plants are those that extract some, or all, of the water and nutrients they need from a host. One of our most recognised tree, the WA Christmas Tree, is a parasite of other plants. Strictly speaking, it is a hemiparasite as it is able to photosynthesise in its own right, but it also extracts nutrients from the plants growing around it.

The WA Christmas Tree, like all parasitic plants, attach to their hosts via a structure called a haustorium. The haustorium penetrates into the living tissues of the host plant and it is through this structure that nutrients and water are absorbed.

Some parasites, like the WA Christmas Tree, attach to their host’s root system and so it is not obvious that they are parasites. Other parasites are completely aerial and attach to a host’s branch. These parasites, commonly called mistletoes, don’t have contact with the ground at all and are completely dependent upon their host for their water needs.

While parasites can place a strain on their hosts, especially if there is a heavy infestation, they also bring ecological benefits. The dense foliage of aerial mistletoes provide perfect nesting sites for many species of bird. The flowers, leaves and berries of all parasitic plants provide food for many more birds and other animals; like the two species of jewel beetles feeding on the flowers of a WA Christmas Tree, below. Overall, parasitic plants do more good than harm and should be enjoyed as much as any other part of nature.

We know of four species of parasitic plants in our bushland – WA Christmas Tree, Nuytsia floribunda; Stalked Mistletoe, Amyema miquelii; Wireleaf Mistletoe, Amyema preissii; and Leptomeria empetriformis.