Controlling Pests and Disease in the Summer Garden

Controlling Pests and Disease in the Summer Garden
In summer the home garden becomes the ideal host to pests and diseases - the temperature is warm, even hot, encouraging insect colonies to reproduce at alarming rates, all growing quickly and feeding on your plants. Warm summer rains increase humidity and moisture lying on the foliage helps the spread of mildew and leaf spot.

We are becoming attuned to the need to spray less and encourage a natural balance in the garden and the best thing you can do is to use lots of Living Earth Biogro certified Organic Compost in the soil, as compost is not just a food source, but is known to encourage plant health and disease resistance. However, do remember that it is okay to use remedies when some control is needed in your garden.

Here is a quick guide to the problems that you will most often encounter in your summer garden and how you can control them:


Powdery Mildew - this attacks the soft leaves of vegetables like the cucurbit family - cucumbers and zucchini; hydrangeas and many summer annuals and perennials. It can occur during a warm rainy period, or from March on, when the nights get cold, but the days remain very warm. Remove diseased annuals entirely to curtail its spread and if you wish, make up a low toxicity spray of 1tsp baking powder and I cup of milk mixed with 1 litre of water. Or, a natural fungicide like copper will work effectively.

Black (brown) Spot - this can mar the look of the leaves on ornamentals such as roses and fruit trees that are in the process of bearing fruit. Controlling the spread should be considered in the earlier parts of the year, but often, by autumn, one lets the leaves fall and gathers them up, because with winter the leaves are to go anyway. Spraying now will clean up new growth and, where fruit is concerned, help keep the plant healthy enough to get the fruit to harvest. Liquid copper is an option, but may look unsightly on fruit, but pip and stone fruit can be controlled with a relevant fungicide - check at your garden centre for the correct one, during the fruiting season.

Rust - Orange pustules on the back of leaves, especially roses are best controlled with a relevant fungicide such as Bravo. If your beans are attacked it's likely its cropping season will be shortened. Often this happens in dry weather.


Nature's Way Pyrethrum (small directed sprays as opposed to the whole garden). Use Yates' Confidor for all three pests for effective longer control - it has a withholding period for edibles and can be used in the rain. A selective pesticide, it only attacks sucking insects, so it won't knock out the predators that you need in the garden for these insects. If you'd prefer to control the fluffy white scale with a natural spray use Conqueror Oil, but avoid spraying in direct sunlight.

Thrips - By the time you notice leaves silvering on evergreens such as rhododendrons or griselinias, it's too late. Spray preventatively now until the end of February with Confidor.

Caterpillars - Major munchies are going on across a whole range of plants - think those white butterflies are cute? Think again - they're laying eggs on your vegetables that hatch into fat caterpillars that munch! Other caterpillars that are eating your garden are the cabbage tree caterpillar (see all the notches in the leaves?) In all cases sprinkling Derris Dust or spraying with No Caterpillars will help eradicate them, but it might take a couple of goes.