Insects and sucking pests remain as one of my biggest challenges growing orchids outdoors. Since I have fish in my garden, using chemical insecticides such as malathion is simply not the best option. They are considered only as an absolute last resort. Morever, these insecticides smell toxic and the stink really gets into my fingers. I don’t think my neighbours appreciate it whenever I bring these smelly guns out.
Neem oil is a good, non-toxic alternative that has worked for me. It comes from the common Azadirachta indica tree which, you may have read, contains Azadirachtin, a compound found to have pesticidal properties (for an excellent guide on neem oil, including its safety and other known uses, read this article here, by Pest Strategies).
Neem oil sprays are available in most nurseries but to save some money, I make my own. It’s really easy and here’s how I do it:
1. I buy a small bottle of neem oil. These are widely available at Indian grocers or sundry shops sold as ‘margosa’ oil.
2. Next, measure out the amount you need. I use 3-5 ml (about 1 teaspoon) to make 1 litre of spray.
3. To get the neem oil to emulsify with water, add a bit of soap. I use liquid dishwashing detergent. You don’t need a lot, just about 2ml is enough.
4. Pour it into a spray bottle and add about 1L of water.
5. Put the spray top with the nozzle back on and it’s ready to use. I give the bottle a shake before each time I squeeze the trigger, to help emulsify the oil further. Spray directly onto the pests, under leaves, or even onto the roots. It has a systemic effect on most plants.
The neem oil spray has a nutty, almost peanut butter-like smell. Some of you may be put-off by it but I find it not altogether unpleasant.
Neem oil spray is effective against spider mites, mealy bugs, thrips and scale. For best results, I use it in at least 3 repeated applications 3-5 days apart. Like any oil-based pesticide, it is recommended that you spray it on your plants during the cooler part of the day. Late afternoons would be ideal. As always, test a small amount first on smaller, more sensitive plants.
Neem oil has been found to work as a fungicide too although I didn’t find this to be the case in my experience.