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Oct. 1996 Vol. 7, #3 BACTERIAL SPOT '96 It's fall and bacterial spot is in the aid! Several growers have asked about the efficacy of different copper (Cu) formulations in controlling spot. So Dr. Jeff Jones of the Gulf Coast Research & Education Center in Bradenton was contacted for guidance. Jeff has been working with bacterial spot for over 15 yrs. and his work basically indicates the following:
A major problem in controlling spot in plant house production is the plant population itself. At 600,000 to 700,000 plants per house it's hard to get good airflow to dry foliage and overhead irrigation splash simply encourages spread. Suggestions for better control in the house include:
USING HYDROGEN PEROXIDE IN GREENHOUSES Alberta - Agriculture, Food and Rural Development, August 1996 M. Mirza, CDC - North, Edmonton (Reprinted from the Penn State Veg. Newsletter, Mike Orzolek, Editor) Experiments in the laboratory have revealed that hydrogen peroxide can reduce the , populations of various disease causing fungi like Fusarium and Verticillium, and can also reduce the development of algae in rockwool blocks. Bedding plant growers, who complain about the growth of slime and algae in plugs and larger containers, when adding hydrogen peroxide to their water supplies reported a reduced incidence of algae and fewer plugged water lines. Seedling tree growers using concentrations of up to 4 percent to spot treat algae and moss growth reported good success. The information below is based on research done at CDC - North, Edmonton, Canada. How to use hydrogen peroxide? - For a water storage tank apply hydrogen peroxide to achieve 100 ppm in the tank. A 2000 litre storage tank will need 571 millilitres of 35 percent hydrogen peroxide. This can be injected into the incoming line or by adding to the tank and mixing well. When injecting, plastic or PVC materials are preferable. If you are using 50 percent hydrogen peroxide then 400 ml in 2000 litres of water will be needed to achieve a 100 ppm solution of hydrogen peroxide. The formula to calculate this is: PPM regd. x Total amt. of water in Litres = gms of hydrogen peroxide reqd. 100 x 2000 = 400 g The result is the amount of hydrogen peroxide expressed in grams. Since one millilitre of water weighs one gram (one millilitre of hydrogen peroxide does not weigh one gram but it is close) the result of the calculation can be expressed in millilitres. When using an injector system, use a separate injector for hydrogen peroxide, once diluted it can be mixed with the fertilizer solution, but inject hydrogen peroxide at the beginning so that any pH changes can be adjusted later. Like fertilizers the amount required to be injected has to be calculated. For example for bedding and flowering plants the recommendation is 50 ppm of hydrogen peroxide in the water. The stock tank is 200 litres and at a dial setting of #10 the injection ratio is 1: 190. This means that 200 litres of stock solution will be utilized in 200 x 190 = 38,000 litres of water. Using 38,000 litres as the amount of water, plug in the figures in the above formula to find the amount of 35 percent hydrogen peroxide necessary. 50 ppm required x 38,000 litres of water divided by 35 percent hydrogen peroxide x 10= 5428.5 millilitres or 5.42 litres. Take the 5.42 litres of 35 percent hydrogen peroxide and mix the 200 litres of water in the stock solution, and inject it through the 1: 190 injection system. A 50 percent technical grade hydrogen peroxide will require 3.8 litres of stock solution to meet the 50 ppm target. Vegetables: Hydrogen peroxide can be used for all vegetable transplants grown in peat moss, rockwool and other growing media. Use 30 ppm for young vegetable transplants right from the beginning of production. Increase the rate to 50 ppm when the transplants are 4 weeks old. Bedding Plant plugs: Use 50 ppm hydrogen peroxide treated water when watering starts. Once plugs have germinated, use 30 ppm as a constant feed along with the fertilizers, after 4 weeks resume the 50 ppm feed. Tree seedlings: Use 50 ppm as a constant feed. At this rate there will be less algae and moss development, and fewer fungus gnats. Growers have used higher rates to spot spray rapidly developing moss on the surface of the plugs. NFT Cucumbers and Tomatoes: Use 30 ppm in the recirculating tank. Hydroponic Herbs in recycling system: Use 5 ppm in the recirculating tank. Underbenches and floor disinfection: 3-4 percent solution once and repeat if necessary. Precautions: Hydrogen peroxide is corrosive and should be handled with care. Use rubber gloves and eye protectants when handling. Hydrogen peroxide becomes inactive once it comes in contact with organic matter like fungal spores, mycelium, algae, dissolved organic matter or other sources of organic material. Iron and manganese present in water can be caused to precipitate out, although at 30 ppm hydrogen peroxide precipitation does not appear to occur. Like many other chemicals, leaf phytotoxicity is possible when hydrogen peroxide is applied under very hot conditions, if plants are under stress, or if the rate is too high. Hydrogen peroxide is unstable, and getting the desired concentration can be difficult. Using distilled water to mix the hydrogen peroxide, covering the stock tank with black plastic and using plastic parts in the injector system helps to improve stability. Once mixed with the fertilizer solution, the hydrogen peroxide will be reduced in its strength, but by that time it's done the job. Having hydrogen peroxide testing strips is useful to determine the final strength being delivered to the plants. Hydrogen peroxide is available as food grade (35 percent) or technical grade (50 percent). It can be purchased in 50gallon drums or in smaller quantities, drugstores usually carry a 3 percent dilution. Hydrogen peroxide is available from dairy supply stores. Worldwide Ozone 403-986-6441, in Leduc, sells it in small or large quantities, also in Edmonton, Van Waters & Rogers at 403-452-6655. Testing strips are available from Herb Martin 403484-0102, there may be other suppliers. Calibrations: 28 millilitre = 1 oz 1 liter = 0.26gal. PLANT HOUSE COOPERATION Do you ever compare one fertilizer regime to another or some new product to your standard or a new tray design? So often comparisons made in the plant house are done so subjectively (I think these look greener or that stem is thicker) that the grower doesn't really know how his/her treatments have affected the plants. Speedling, LaBelle Plant World, and CollierGro have all asked us to tabulate plant characteristic data (height, stem diameter, color, leaf area, root weight, etc.) for them concerning in-house trials they conducted last year. This service is one we offer gladly in the spirit of cooperation and has helped these companies make educated decisions about modifications in plant house practice. We'd be glad to work with you too. Just let us know how we can help. COCONUT COIR Last spring we tested Scott's "new" coconut coir (fiber) as an alternative media for tomato and pepper transplant production. The coir tended to run moist, but essentially produced a plant that was similar in appearance to a standard peat media plant. Once planted in the field, coir transplants grew and produced similar to peat raised transplants as well. We will continue with our coir trials in the fall and will keep you updated. Should you wish to review the full spring trial test results please call and ask for SWFREC Station Report - VEG 96.7. Until next time, Charles S. Vavrina |
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