What's Wrong with my Shrub?

iannJanuary 1, 2013

Shrubs in trouble

Shrubs are a generally trouble-free type of plant. Mature shrubs can generally shake off insect and larval attacks, handle fungal diseases, and get through occasional droughts or floods. The occasional pruning of dead branches is often the only maintenance they need for years on end.

Unfortunately, things can go wrong and sometimes you need to help out. Often, a little TLC, fertiliser, attention to watering, and judicious pruning, is all that is needed and the shrub will recover on its own.

Leaf problems

Why are there holes in my leaves?

Usually, holes in leaves are caused by insects or insect larvae. The first step is to identify the culprit. Neat round cuts in the edges of leaves indicate leaf-cutter ants or wasps, while skeletonised leaves are caterpillar attacks. Once you have identified the little monster you can choose a means of control. Unless the attack is very severe, you can generally just let things take their course and the shrub will be fine.

Occasionally, fungus can cause distinctive holes in leaves. Small dried-up patches on leaves tear into ragged holes as the leaf grows. Again, unless the attack is severe there is no need to treat this.

What are these dead lines on my leaves?

Grey meandering lines visible on leaves are the result of leaf miners, small larvae that live inside the leaf and eat it. They rarely damage the health of a plant, but can be unsightly on broadleaf evergreens. Minor damage can be treated by removing affected leaves. Severe infestations must be treated with a systemic insecticide.

Why are my Cherry/Peach/Almond leaves all curled up and dead?

Many flowering Prunus shrubs and trees are prone to Peach Leaf Curl, a fungal disease that attacks the leaf buds and sometimes the flower buds. It causes the mature leaf to be deformed, turn brown and crispy, and to drop prematurely. Treatment must be preventative with fungicide being applied after leaf drop and before bud burst. With repeat cases, the best approach is to replace with a resistant variety.

What's that black stuff all over the leaves?

Uusually back sooty deposits on leaves and branches are a fungus growing on sap produced by insects. It is not unhealthy for the shrub, but is unsightly. These can be aphids, but on shrubs the cause is often scale, small bumps on stems and underneath leaves. Again, this is rarely damaging to established shrubs. Treatment is to physically remove with your thumbnail or a small stick. Severe infestations can be sprayed with horticultural oil, but follow the instructions carefully since it can be toxic to the plant. Insecticides are rarely effective against scale.

Why are leaves dropping off my shrub?

Most evergreen shrubs drop some old leaves each year and this is perfectly normal. Even deciduous shrubs can drop older leaves during the summer and obviously drop them all in the...

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