Thanks for joining me again for the second in my “Citrus” series of blogs. Today I’ll be discussing some of the pests which frustrate fruit-growing gardeners, and what can be done about them without using harmful chemicals.
Fruit Fly
This blog would not be complete without some information on the control of Fruit fly. This is the most significant fruit pest worldwide, and undoubtedly the hardest to control, so don’t feel bad if this is your main citrus problem. They are attracted to the smell of ripening fruit and lay their eggs beneath the surface of the skin. Their larvae, once hatched, burrow inside and cause the fruit within to rot and possibly drop prematurely. A combination of approaches is your best bet for control:
1. Buy a variety that is heaviest in fruit toward mid to late winter when the pest is least active. Read the label carefully.
2. Use fruit fly bates – Ceratrap is the most effective that I’ve come across and is developed for the specific fruit fly we have in Perth. You need to refresh this regularly throughout the fruiting season.
3. Cover your tree with mosquito netting or specifically designed netting available from some nurseries.
4. If you are lucky enough to have chooks, they can make a huge difference to the populations of fruit fly in your garden because they scratch up and eat the pupating larvae in the soil.
Citrus leaf-miner
The larvae of this tiny moth makes it’s home under the surface of the leaf and makes a disfiguring squiggle as it munches it’s way to adulthood. It’s a minor pest as it won’t affect the fruit production but can be annoying if you’re growing kaffir lime leaves to eat or if you’re interested in the aesthetics of your tree. The easiest way to control this pest is to limit your fertiliser routine to the winter months in Perth. They are most active during summer and autumn and ensuring that your flush of new growth is well before this time will ensure that the leaves are hard enough to withstand attack in the summer. If you have an outbreak though, effective control can be made on a small tree by spraying with eco-oil and hand picking every few days.
Scales, Mealybug, Aphids
Sap sucking insects happily invade citrus and can make a nuisance of themselves by depleting the plant’s energy and excreting honeydew which in turn covers the leaves and fruit in a sticky black mould (Sooty mould). This doesn’t affect fruit production too severely and you may find that in time natural predators like ladybird beetles will start to manage the populations, so don’t be too quick to spray.
As with the citrus leaf-miner, sap suckers are attracted to soft new growth. Avoiding fertiliser application, especially high nitrogen fertiliser (such as fresh sheep manure) in the spring can minimise a soft, sappy, growth-flush when they’re most active.
Ants are often at the heart of your sap sucking problems – the clever little things farm the aphids and other insects for their honeydew excretions. Banding the trunk of the tree with a horticultural glue can work wonders.
All photographs courtesy of the WA Department of Agriculture and Food at https://www.agric.wa.gov.au