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Griffin Greenhouse and Nursery Supplies, Inc.
Rick Yates, Technical Support Manager
ryates@griffinmail.com |
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| Sanitation remains the front line of defense for controlling diseases in propagation areas. Weeds not only harbor insects but many diseases as well. Physically remove weeds from the greenhouse, or use an approved post-emergent herbicide such as: Finale®, Scythe™ or Envoy® (grasses only). Caution: There are no pre-emergent herbicides labeled for greenhouse use! Growers who have disregarded label cautions against their use in enclosed structures suffer considerable crop damage each year. Clean the propagation area to remove algae and kill lingering diseases with Greenshield®, Zero-Tol™ or GreenClean™, which is described in the New Products section of this newsletter. The granular formulation is very easy to use. Cleaning these areas not only reduces your disease potential, it also depletes the food supply for fungus gnats and shore flies that are known to spread diseases as they move around your crops. |
| Optimize your mist system to produce small droplets of water. Large water droplets can over-saturate rooting media and increase moisture on the floors of the greenhouse. Your Griffin salesperson can help you determine if you are using the best nozzles for the job. Some growers have reduced water requirements by covering cuttings with Reemay® row cover. This allows air and light to pass through while increasing humidity under the cover. Misting can be reduced and stopped sooner with this approach. Peter Konjoian has conducted valuable research on using the surfactant CapSil™ to reduce misting requirements and hasten rooting by spraying or dipping the cuttings. Please refer to the summer edition of the Griffin Gazette for more details. Any steps you can take to reduce rooting time and/or the amount of mist needed reduces your disease potential. Root zone heating can shave additional time off of the rooting process. Griffin's Construction Department has experts ready to help you examine the options available for controlling rooting media temperature. |
| Fungicides can also be useful when environmental conditions favor disease expression. Rhizoctonia can be a problem in cutting propagation. FungoFlo®, Cleary's 3336®, and Medallion® may be used as soil drenches for this disease, as well as being labeled for use as foliar sprays to control aerial rhizoctonia and botrytis. This issue of the Gazette features FungoFlo® as the Super Saver item, be sure to look for it. Botrytis is the foliar disease problem most often reported by propagators. |
| The host range for botrytis is extensive, and free moisture on leaf surfaces makes the propagation a high-risk area for infection. Decree™ has proven to be a valuable tool in combating botrytis. Two hours of drying time are all that are needed to make Decree™ water fast on leaf surfaces, an obvious advantage in the propagation environment. |
| Other effective chemicals for botrytis include: Chipco® 26019, FirstStep™, Pathguard™, Phyton-27®, Spectro® 90 WDG, and Zero-Tol™. Pythium and Phytopthora root and stem rots are other significant pathogens that can capitalize on the warm wet conditions of the propagator. Use the low end of the label rates for Banrot, Subdue Maxx, or Truban if needed. Generally, fungicides applied as soil drenches can cause some inhibition of rooting. Do not use these products preventively on unrooted cuttings, use the "see and treat" approach instead. Treating stock plants in advance of taking cuttings is a strategy that has helped growers introduce less disease to the propagator in the first place. If you produce your own stock consider a preventative program for root rots and foliar diseases. |
| Griffin makes available, a bulletin containing rates, use patterns, cautions, and re-entry times for many common insecticides and fungicides. Request your free copy of, "Insecticides and Fungicide Options for 2001", from your Griffin sales representative or call your local Griffin branch. |
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