Galls are growth malformations caused by the stimulus of an insect, small animal, fungal or bacterial attack. Insect feeding, insect egg deposits or fungal/bacterial infections may result in an increased level of hormones flowing to the site of irritation. This promotes abnormal growth around that point which leads to formation of galls. Galls vary widely in size and shape, and the shape of a gall may be specific to its causal agent.
Galls should be removed manually and destroyed when first noticed, in case they are caused by insects. This will curtail a build-up of the insect pest. Chemical control with systemic insecticides is usually ineffective. Good general health and vigour of the trees is the best prevention of gall damage. Keep up water and nutrient supplies to the plant.
Ink disease is an attack by a fungus called Alternaria alternata which affects kangaroo paws. Ink spot shows up as blackening of the leaves and flower stems. The disease usually starts at the leaf tips, then spreads down the leaves into the rhizomes. If uncontrolled, ink spot may kill weak plants of dwarf hybrids and kangaroo paw species including Anigozanthos manglesii and A. viridis. More vigorous species, like A. flavidus, are resistant to infection.
A range of cultural control measures can be tried. Manipulating the microclimate, as well as nutrient modifications can be of benefit. The best way to control fungal diseases is to keep the plants vigorous and healthy. The addition of essential trace elements, especially potassium and calcium, may improve the vigour of the plants and reduce the plants’ susceptibility to ink spot. If the plants are situated in a shady, cool, moist environment either move them or increase ventilation and sunlight by thinning neighbouring and overhanging plants.
Cut foliage affected by ink spot off at the base to encourage healthy new foliage.