Article 5-3 Fungus Gnats
By Erik Biksa
Love the web site and in particular the information on fungus gnats. I am in Australia. Was wondering what the control for fungus gnats is in newer growing mediums such as perlite. I have used scarid fly drench on continuous watering for 16 hours and two five minute waterings two hours apart. (Active constituents- Azadirachtrate 90% & Liminiods. I rang a local retailer and he said to run for another 24 hours at normal watering cycles. Would this be too much? The nutrient level is up to 1960 EC. I would like to dump the nutrient and replenish with nutrients and a systematic fungus control, using a product called Fungarid. Would this be the correct course of action?
The gnaticides you have referred to are not commonly used in this part of the world (British Columbia, Canada), so I have to say that I am not entirely familiar with them. However, you have mentioned that you are considering applying a systemic fungicide. I am not familiar with any safe systemic fungus controls although there are a number of supplements that's claims include increased resistance to fungal pathogens and subsequent infection. Biological controls are preferred as they promote higher crop sale value, often need to be re-applied less frequently, can be less expensive to apply, have a higher level of persistence, and can be considerably kinder to the consumer.
Nemasys, are a strain of beneficial nematodes (roundworms) called Stienernema feltiae that aggressively attack the potentially harmful fungus gnat larvae. Fungus gnat larvae can introduce diseases such as viruses into the host crop. The adults are a nuisance that produce the harmful larvae. The predatory Nemasys can be purchased and are shipped live.
For fungus, a spray of un-pasteurized whole milk (one part to 10 parts water) is effective in controlling powdery mildew if detected early enough. Naturally occurring Chitinase can be effective in strengthening plants to resist foliar diseases. Biological enzyme inhibitors also offer a level of prevention and control.
Evaporative sulfur or elemental sulfur sprays will also provide relief. For organic growers, some use nettle tea or colloidal silver applied as sprays. It's great to have some insight from your part of the world, and I thank you for giving me some controls to research.
Cheers, Erik Biksa