Ask Erik - Letters to Maximum Yield

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 pearlite. I have used scarid fly drench on continous 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 cyles. 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 systamatic fungus control, using a product called Fungarid. Would this be the correct course of action?
Regards, Peter.

Peter,
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 foiliar diseases. Biological enzyme inhibitors also offer a level of prevention and control. Evapourative 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

Can I buy garlic spray, if so could you please advise where I can get a bottle or can. I live in Thornhill, Ont.
Thank you

Garlic has been demonstrated to be effective in repelling insects from crops. Theoretically, insects view and judge plants from a “glow” that plants emit. Often, insects will attack weaker plants first. This is perhaps due to the weaker plant emitting a different “glow” than it’s healthy counterparts, enticing the insects. When garlic is sprayed onto the plant, it is thought to change the glow a plant emits, making it unattractive to the would-be-pest. Horticultural garlic sprays such as Garlic Guard are available from independent hydroponic retailers. Consult your the dealer listings in the back of Maximum Yield magazine for the one nearest you. Alternatively, concentrated garlic sprays are marketed for cooking purposes (sure beats chopping all that garlic, and it’s obviously food grade!). You could also easily make your own garlic spray at home. In a blender, add a few cloves of mashed or chopped garlic to a liter of warm soapy water and blend. The dish soap acts as a wetting agent, increasing the effectiveness of the spray. Use a natural soap such as Ivory. Allow the mixture to stand overnight and strain through cheesecloth or coffee filters before adding to a sprayer. You may also consider adding cayenne and cinnamon to the mixture. Both have been shown to be beneficial in combating insects.
Cheers, Erik Biksa

I am working with a family which is raising hydroponic tomatoes (loose, not clusters or cherry). We need to be able to establish a “normal/expected” yield and we do not know where to obtain that sort of information. Can you point us in the right direction?
Connie Skinner

Connie,
Thanks for your question. If growing in a well-managed hydroponic environment, light duration and intensity will play a strong role in determining the yield potential of the crop. In a hydroponic greenhouse environment, 35 + kilograms of fruit harvested per meter square during a four-month harvest period is probably about par. I suggest contacting the Canadian Greenhouse Crop Processing and Research Center (GPCRC) in Leamington, Ontario. I haven’t taken note of what they have been up to lately, but in the past they have done some cutting edge research followed by public reports on growing many crops, including hydroponic tomatoes.

Sincerely, Erik Biksa