By- Mick O’Brien Dip.Hort (MAIH)
Wow, if it is not citrus leaf miner- Phyllocnistis citrella, destroying the new succulent flush of delicate leaves growing on our citrus trees or the powdery mildew on zucchini, pumpkin and cucumber or the bacterial and fungal wilt diseases in tomato or the fruit spotting bugs in pawpaw, citrus and mango - Amblypelta lutescens or A. nitida, or the dreaded cabbage moths or butterflies laying eggs in any of the healthy green leaves of the remaining thriving silverbeet after the lovely rainfall of late- you will be forgiven for having second thoughts of retreating this season and letting the pests feast away while momentarily feeling you are losing the battle! If a few of these pest and diseases are affecting your patch this month, then you will identify with the frustrations at hand trying to produce your own food without using toxic insecticides. And of course being an honest gardener and not one to be afraid to admit that if any of my plants succumb to disease that is, I have learned to adapt to the occasion as a result. I have laid pheromone traps in citrus to confuse the leaf miners, sprayed Eco-oil, (a natural botanical based oil to deter any eggs being laid), pulled any diseased tomatoes or capsicum plants out of the patch seemingly affected from the (Tomato leaf curl virus which is transmitted by sap sucking greenhouse whitefly larvae) feeding enmasse - and by diligently spraying all remaining silverbeet, bok choi and broccolini - with Bacillus thuringiensis - Dipel® (a natural bacteria that stops the caterpillars feeding), to ensure some harvest is at hand, but still no synthetic insecticides are used, nor have I covered my crop with netting yet, an act of defiance I know! It all comes down to getting serious if you want to feed your family and enjoy your fresh home grown produce, we need to choose crops that will prosper in our climate and handle the humidity for starters and secondly is their resistance to disease - if any, and searching for known cultivars or hybrids that are stronger and produce more prolific fruits. Now, unfortunately some of the agricultural pests we have in plagues currently are so rampant due to the overuse of synthetic insecticides over time by farmers in the past, which contributed to killing off the natural predators that control these pests naturally too, so it’s very important we try and encourage all the beneficial insects that will predate on your pests back into your patch.
So what can we do? Well the professional farmers have cottoned on, (pardon the pun). Some are using bio-control predators that will feed on their host pest such as the dreaded Silverleaf whitefly on tomatoes or cotton plants with predators such as the tiny exotic wasp- Eretmocerus hayati, which was originally introduced from Pakistan or the predator wasp- Encarsia formosa, which are both commercially available by bio-control rearing farms such as - Bugs for bugs. Also I should note that these predator wasps are extremely sensitive to insecticides, so we have to lay off the chemical’s folks to keep the balance in check. By doing the research on our most common pest and diseases affecting us in the great south east, you may delve deeper and find you can source seeds, cultivars and grafted varieties which can readily withstand our climate and show tolerance to the mainstream pests and diseases we face today. Interestingly, it is possible to do your own grafting with a strong root stock- to your favourite compatible scion (the above cutting) and this can be done with tomatoes by simply grafting your favourite tomato species onto an eggplant root stock for example. This will provide an extremely strong root system for a profusely abundant fruit producing tomato plant that would otherwise not have the stamina to hold up to growing in the subtropics. But if your soil already harbours pests or diseases from sick and dying Solanaceae family members - such as tomato, capsicum, or chilli etc, then do not replant next years crop in the same location. Try growing Brassicas or rotate with light feeders such as alliums as part of a good crop rotation system.
There are grow bags available for purchase that look like potting mix bags and these can be placed on the ground or in a garden bed, simply cut a slit into the top of a bag and insert your seedling and supporting stakes. When your harvest is over you can dispose of the bags and start again. This limits the necessity of crop rotation in small garden spaces and helps keep nematode problems at bay and saves having to solar sterilise the soil with plastic to start all over again. So do not give up folks, get smarter, source disease resistant cultivars and with good hygiene practice, sterilising tools and by planting grafted varieties- you will see a bountiful harvest or perhaps, I may have inspired you to actually try grafting. I hope so, take care all. The Happy Horticulturist.