Summer Pests and Diseases

During the hot humid weather of summer, your gardens are potentially at risk of all kinds of pests and diseases.

Humidity brings on a lot of fungal diseases, such as Powdery Mildew. This will target plants like soft leafed vines, such as Cucumbers, in your vegetable patch. It also affects a number of ornamentals, such as Agapanthus and Crepe Myrtle.

You can use various products to counteract Powdery Mildew. But one major thing you can do, to reduce its occurrence in the garden, is to limit overhead watering, such as micro spray irrigation and hosing. Often this can be done by using drip irrigation or by placing a dribbling hose at the base of the plant.
I recently had to deal with Powdery Mildew on Agapanthus in a customer’s garden. Much of the foliage had to be removed along with the brown sheath that you find at the base of the plants along with all of the wilted leaves. Then I sprayed with a combination of Pestoil and Confidor which is repeated again, in a fortnight. After that the plants grow healthy green leaves, free of the disease for a long time.
Another disease which is prominent at this time of high humidity is Black Spot on roses. Again, a reduction in overhead watering will help reduce this disease. Otherwise, you can spray on alternate fortnights with Yates Rose Shield and Eco-Rose with Eco Oil which will ward the disease off.
Pests at this time of year include Stink Bugs and Spined Citrus Bugs. The program to reduce these starts in spring before you can really see them. Give your Citrus an oil spray with Pestoil to target the tiny juveniles. Then, as survivors appear, the most effective method of killing them is to apply extreme pressure on their heads between your thumb and forefinger! If you grab them quickly from the front they can’t squirt you with their toxic acid spray. Wearing safety glasses is a good idea. When the temperature exceeds 40 degrees Celcius, they will all crawl down to the bottom of the tree and sometimes in the mulch at the base of the tree. They are easily dealt with at these times. It just involves you going outside into the hot weather.

I don’t like using toxic chemicals to kill pests because you don’t want to be eating the stuff.
Another type of pest which appears in summer are various forms of scale and mealy bugs. If you can pinch or trim off growth on plants to remove as much of these as possible, that will keep them down. But you need to keep doing it. On things like Orchids, you can reduce mealybug and soft white scale by dabbing methylated spirits onto them with cotton tips. Then give them an oil spray. You can use Confidor with Pestoil to spray them after that. Again, keep the overhead watering to a minimal, though excessive rain in summer can increase their numbers.
In the end, the most important things to minimise pests and diseases are to avoid creating an environment which pests like and eternal vigilance in the garden.