Pest watch
pests will not just attack weak plants – they will attack anything. However, if you know what to expect and keep a close eye on your crops, you can prevent and treat problems organically.
timing is also important. Many pests and diseases have a particular period when they’re most prolific. Carrot rust fly, for example, goes in cycles. if you can avoid sowing your crops when the adults are busy laying their eggs, you can often avoid an infestation. in south canterbury, we sow carrots and parsnips in september, before the adults appear, then again in november, January and March. October, december, February and april are the main periods during which adults are active and eggs are hatching.
Carrot rust fly is also lazy and doesn’t like to fly very high. you can block the carrot bed with a bit of knitted polyethylene (Mikroclima, which can last for years), or even shade cloth, which can stop the flies getting into the crop. Raised garden beds are also good for prevention.
“The rust fly is lazy: it will go somewhere easier than having to fly up over a barrier. Organic gardening is about working with insects, rather than fighting against them.”
attracted to the smell of the carrots and parsnips, carrot rust fly can also be deterred if crops are sown thinly (so the fly cannot smell the carrots and parsnips when you thin them) or surrounded by onions, spring onions or other heavily scented crops (which is why carrots and onions are great companion plants – turn to page 56 for more on companion planting).
Marigolds are the best companion plants, she says. choose african or French marigolds as the secretions in their roots help repel common soil pests, such as nematodes.
it helps to know what insects are going to be attacking your plants and what you can do about them. Take the white butterfly, for instance. early crops in before christmas will be visited by the caterpillars and butterflies, and those we spot can be squished. However, further down the track, from december to February, these pests will be out in force – and hard to keep up with. pest control products, such as yates success ultra insect control concentrate (with spinetoram, derived from beneficial soil bacteria), or those with Bacillus thuringiensis (a bacterial toxin), will kill the larvae of the insect without affecting humans. There should already be signs of damage, such as holes in the leaves, before using the products, and you need to apply them generously, with good coverage and with regularity – every seven to 10 days.
Another option is to cover the crop so white butterflies can’t get in and lay eggs on the leaves. The butterfly has to touch the leaf to lay its eggs, but it can still do so through the covering if it is touching the plant. so, ensure there is a good space between the cover and the crop and raise the cover height as the plants grow. if you spot eggs, brush them off; if you see caterpillars, squish them.
codling moth also needs regular monitoring. try putting pheromone traps out around november to January to catch the adult male moth. the aim is to limit the number available to fertilise the females. ensure you replace traps with new ones each year and keep checking them throughout the season.
when moths appear, however, you already have a problem. Hygiene can help – make sure dead apples are cleaned up every season. You can use chooks and ducks to find and eat the cocoons (which may be wintering over), while a spray of lime sulphur on the trees over winter can break away the lichen in which pupae hide in cocoons, buried in the bark. these types of approaches can break the cycle.
Know your pests and diseases. Keep an eye on everything, and when you get a problem start doing something about it without immediately resorting to a spray. And be prepared to accept some damage – our gardens don’t need to produce perfect veges like in the supermarket. If you have a few bugs, just wash them off!