Summer’s here and the pests are having a party at the expense of your vegie patch. There’s a general yellowing, and some strange furry growths… That seems like a fairly typical warm summer period in the garden to me. It can, however, be reduced and even avoided with some attention to how you plant and some growing methods that work with cycles, not against them. The warm weather brings us out to enjoy the garden, visit beaches and go on bush walks – and it’s the same for pests and diseases; they’re most active and prevalent during the warmer months. Like many things in the world, pests and diseases are manageable once we know how they work and what their cycles are. The reproductive cycles of many insects are centred around this time of year, with hatching, mating and feeding all taking place from spring through summer. The same applies to diseases, some of which have certain temperatures above which they begin to proliferate.
So the warm summer months are a time when we need to be especially diligent regarding pest and disease control. The most valuable tool in managing these problems is observation; a quick daily check will keep you up to date on changes and any unusual occurrences. Be on the lookout for damage to your plants including chewed leaves, distortion, wilting and yellowing. Do insects fly off when the plants are disturbed? What about powdery coatings on the leaves? This is what’s called the ‘Host (plant)/Pathogen (pest) interaction triangle’ (image to be done/added). It’s fairly simple. The survival of both the host and the pathogen depends on environmental conditions and an adequate food supply. If the environmental conditions favour the pest or disease, the plant will suffer. If the environment favours the plant over the pest, the pest will suffer. If the plant is not a food source for the pest, the pest will suffer. By relating garden problems to this triangle you can often manage an issue with a simple change and dramatically reduce the negative outcome. The change may be switching plant varieties to ones better suited to the environment or the growing time to avoid a problem.
The best way to reduce problems in your garden is to keep your plants healthy. This should be done in a balanced way, with good soil preparation, incorporating organic matter and fertilisers. It’s a good idea to use a combination of powdered inorganic and organic products, as the organic materials and fertilisers fortify the soil and encourage worms et al., while the inorganic ones give things a kick start. Gardening success really does start from the ground up, so maintaining soil health is the key; the quality of your soil will transfer to your plants and affect their health and development. Be careful not to use too much nitrogen as this will just make the plants soft and reduce fruiting, especially for Tomatoes. Your watering system is also important as wet foliage, especially later in the day, encourages fungal diseases, snails and slugs. Drip-irrigation systems are a great way to reduce water use and eliminate these problems. Mulching around your young plants stops water loss from the soil surface and reduce weeds. Weeds harbour pests and diseases so keep them under control too. It’s not always easy, depending on the size of your garden, but allowing more space between plants and rows will assist the reduction of disease. Set up a system to rotate your crops through each year to reduce the pressure on the soil and plants. If plants aren’t taking the same nutrients from the same area of soil every year, pests and diseases don’t have a direct re-entry point to their host plants. Don’t re-plant poorly performing or susceptible varieties back into your garden either; try different ones until you find a good performer. Many of these things are simple but effective, and when pieced together your summer vegie crop will flourish. If you work with nature, rather than against it, you’ll find nature will also work for you.
The advent of summer brings some very common problems, so let’s look at them and how they can be managed. Common summer plant pests:
Aphids
At this time of year, with lots of lush new growth, aphids will be common. Be vigilant; a quick squash between your fingers will help to keep the population down as long as you do it every couple of days. You could hose them off or have a hand sprayer with soapy water. There are a number of natural predators around, the best one being the small black wasp, so keep pesticide sprays a last resort. If you have large numbers of aphids, prune off the affected plant part. If you must spray, white oil, which smothers them, or the organic pyrethrums are good choices. Plants that repel aphids are: Chives, Garlic, Nasturtium and Spearmint.
Caterpillars
These are common and there are a lot of different types. The most common that you’ll see fluttering around your vegie patch is the Cabbage White Butterfly. It can be recognised by the black spot on its white wings. The larvae, which grows to around 40mm long, is green with a fine, yellow stripe down its back. Like most caterpillars, the Cabbage White have voracious appetites and can destroy young plants in a single day. Get the kids to help with caterpillar hunts, then pick them off and squash them under foot or with your fingers if you’re not too squeamish. They are soft-bodied so can be dusted with lime to antagonise them or sprayed with either white oil or a brew of vegetable oil with a little detergent from the pantry.
Beetles and Bugs
Bugs isn’t just a common name, but a name applied to a group of insects that suck sap. One to watch out for is the Bronze Orange Bug, sometimes called the Stink Bug, which sucks sap from the shoot tips of citrus trees. Pick them off into a plastic bag and let bake in the sun. There are also the Spined Citrus Bug and Green Vegetable Bug, both of which are smaller green versions of the Bronze Orange Bug. Beetles can occasionally be good for your garden, but you’ll find that is the exception rather than the rule. Adult beetles and their larvae chew leaves and can do quite a bit of damage. In particular, watch out for the Curl Grub, which is the larvae of Christmas Beetles, and the African Black Beetle; the adults only chew leaves but the larvae can kill plants by eating their roots. Chooks scratching around are good remedy for these beetles, providing a regular turning of the soil. Plants that may assist to repel beetles are, Nasturtium, Rosemary and Thyme.
White Fly
These are commonly a problem for Tomatoes, especially if the plants are kept on balconies or in a protected garden. They are small, 2-3mm long white flies that swarm almost as a cloud when disturbed. They spread viral disease, so they should be controlled or a wide range of plants will suffer. A good solution to the white fly is the vegetable oil spray, or to plant some Nasturtium, which may have a natural repelling effect.
Fungal disease
It’s hard to provide an all-encompassing solution when many diseases are quite specific in what they attack and how they infect plants. We can, however, apply some useful general rules to the management of plant disease which will assist greatly in your endeavours. Fungal diseases characteristically need moist, humid conditions. In a garden we accidentally create an environment hospitable to fungal disease by planting too densely, which reduces air movement. We also water overhead, wetting the foliage and providing the opportunity for diseases to settle in. This goes hand-in-hand with a tendency to overwater, creating a very moist soil that many root diseases use to the detriment of the plant. We are lazy with the turning of our soil and don’t incorporate organic matter, which antagonises diseases. There are a couple of simple remedies for all this. Use drip irrigation and water the soil directly, reducing humidity and eliminating the wetting of foliage. Space your plants a little further apart; they’ll grow quicker and be a little larger so the loss becomes a gain. Apply a layer of organic mulch like lucerne straw to the soil surface regularly, that way the soil organisms can do your digging for you.
Your garden should be a place you enjoy. It can be off-putting when all your efforts seem to be consumed by the pest war in your patch. Try a few of these ideas and the results may surprise you. You’ll be glad you persevered when you’re grazing fresh vegies from your patch.
Words by Peter Abell