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| Greenhouse Alert newsletter | ||||
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| No. 2, January 2008 |
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This month's articles Temperature variation within a greenhouse 2007 Insect Controls for the Greenhouse Industry wall chart available New Michigan driver’s license requirements in effect Greenhouse growers Greenhouse*A*Syst and MAEAP program open house Insects and mites are active now Greenhouse*A*Syst: A free tool for growers Environmental assurance for greenhouse crop growers |
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| Temperature variation within a greenhouse January 30, 2008 -- In the production of greenhouse crops, plants are grown on the floor, on benches, or overhead in hanging containers. In each of these locations, the temperature and light environment can be considerably different. Growers are most familiar with the temperature variation that can exist horizontally within a greenhouse. For example, flowering can be delayed in crops grown adjacent to a cold sidewall compared to crops grown in the center of the greenhouse (Image 1). Temperature variation can also occur vertically within a greenhouse, from floor to ceiling. With the increased need for energy-efficient production, growers have asked us how much temperature varies between the floor, the bench, and overhead. We didn’t have any data, so we conducted an experiment to help answer this question by measuring the air temperature at different vertical positions above the floor in one of our research greenhouses at MSU. In the center of a greenhouse section, we placed a thermocouple at four different heights above the concrete floor: 0 ft 6 in, 3 ft 6 in (bench level), 6 ft 6 in, and 9 ft 6 in. Each of the thermocouples was inserted into a 2-inch diameter white rigid PVC pipe that was positioned vertically in the greenhouse (Figure 2). At each thermocouple location, small holes were drilled into the sidewall of the PVC pipe and a 2-inch diameter fan forced air across the thermocouple. The thermocouples were connected to a data logger that measured the temperature every 10 seconds and recorded hourly averages. We collected data with horizontal air flow (HAF) fans off or on for 8 days each. |
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| As expected, the data collected indicate that the average air temperature within the greenhouse increased as the distance above the floor increased. However, the magnitude of temperature variation depended on the time of day and on the operation of HAF fans (Figure 3). The greatest temperature variation occurred during the day and there was generally little difference with and without HAF fans operating during this period. For example, during the 8-day period with HAF fans on, the air temperature near the floor during the day was on average 1.2 °F (0.7 °C) cooler than at bench height, and 3.0 °F (1.7 °C) cooler than 9 ft 6 in above the floor.
The use of HAF fans was most important during the night. For example, during the 8-day period, the average air temperature at night near the floor without HAF fans was 1.2 (0.7 °C) cooler than the temperature at bench height, and 3.3 °F (1.9 °C) cooler than 9 ft 6 in above the floor. When the HAF fans were operating during the night, the air temperature near the floor was similar to bench height and only 1.9 °F (1.0 °C) cooler than overhead. This study provides an example of how much temperature variation can exist vertically in a greenhouse during the day and night with and without HAF fans. The magnitude of temperature variation will vary from one greenhouse to another and is dependent on the size and structure of the greenhouse, HAF fan characteristics, humidity, etcetera. These results also demonstrate the importance of using HAF fans especially during the night to mix warm air overhead with cool air on the floor. Are HAF fans installed and working properly in your greenhouse? For more information on the benefits and installation of HAF fans, read John Bartok’s article, available as a pdf file through the MSU Greenhouse Energy Resource website. |
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Figure 2. Experimental setup used to measure air temperature at four different heights above the greenhouse floor. At each height, air temperature was measured with a thermocouple that was aspirated with a 2-inch diameter fan. |
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Remember that plant temperature, not air temperature, controls how fast or slow plants develop. Plants can be several degrees warmer than the air under high-intensity lighting and when it is sunny. In contrast, plants can be several degrees cooler than the air during the night, especially when humidity is low. Plant temperature can be easily measured with a hand-held infrared thermometer. This practice can give you an idea of how plant temperature varies from the air. In conclusion, we encourage all growers to position their covered, aspirated temperature sensors at crop height. As our data shows, temperature measured just 3 feet above a crop can be a little warmer than at crop level. Thus, a temperature sensor mounted above a crop can lead you to believe that crops are growing at a warmer temperature than they actually are. |
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Figure 3. Measured air temperature at bench height (3 ft 6 in) and at 3 different heights above the greenhouse floor with or without the operation of horizontal air flow (HAF) fans. Data was averaged for 8 days with HAF fans on and 8 days with them off. The daylength was extended with high-pressure sodium lamps to provide a 16-hour photoperiod (from 6:00am to 10:00pm).
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| 2007 Insect Controls for the Greenhouse Industry wall chart available January 24, 2008 -- This July 2007 revision lists 59 insecticides labeled for greenhouse floriculture production. It provides detailed information on mode of action, insects and mites, labeling on herbs and vegetables and notes on their usage along with other valuable information. Every greenhouse grower should have a copy hanging on the wall near their pesticide storage area. The 2007 Insect Controls for the Greenhouse Industry bulletin (E-2696) costs $5.00 and may be ordered online using a credit card (http://www.emdc.msue.msu.edu/) or by mail or phone using the address below. You may also contact your local MSU Extension office to order a copy. MSU Bulletin Office 117 Central Services Michigan State University East Lansing, MI 48824-1001 Phone: 517-353-6740 Fax: 517-353-7168 Office Hours: M-F 8:00 AM to 5:00 PM |
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| New Michigan driver’s license requirements in effect January 24, 2008 -- Secretary Land announced a significant change in Michigan's driver's license requirements for first-time applicants to take effect January 23, 2008. Based on an opinion by Michgan's Attorney General (AG), Michael Cox, answering a request from State Representative Rick Jones, which replaces the 1995 opinion of former AG Frank Kelley, Secretary Land issued the new requirements yesterday. The new requirements, similar for state identification and for an original Michigan driver's license, include a valid Social Security number (or proof of ineligibility), permanent legal presence in the United States, identity (showing name and date of birth), and Michigan residency (at least two documents). A list of acceptable documents is available at www.Michigan.gov/sos. The permanent legal residence requirement means that only citizens and permanent legal residents will be able to apply for a new driver's license. All temporary residents, including foreign students and professionals (e.g., in the U.S. up to six years with H1B visas) cannot apply for a Michigan driver's license. Details on the application requirements can be found at http://michigan.gov/documents/sos/Applying_for_lic_or_ID_SOS_428_222146_7.pdf . At this point, the new requirements only apply to first-time applicants and it is unclear how the AG's opinion will be applied to renewals. Although Land pointed out that the number of original applications processed in branch offices is less than 4 percent of all branch transactions, these requirements are expected to increase the number of unlicensed and uninsured drivers on Michigan roads. |
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| Greenhouse growers Greenhouse*A*Syst and MAEAP program open house
January 24, 2008 -- Please join us to learn about how to asses your current agricultural business practices to assure we are doing our part to eliminate potential practices that may be a risk to ground and surface water. There is no charge to attend the open house. When: Tuesday, January 29 |
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| Insects and mites are active now Thomas A. Dudek District Extension Horticulture and Marketing Educator It’s cold outside, but it’s warm and toasty inside greenhouse ranges and insects and mites are active in area greenhouses. We are getting reports of newly arrived cuttings and overwintered plants having active insect and mite pests on them now. Check incoming ivy and zonal geranium cuttings for broadmites. They are extremely small to see without a microscope, but the damage is evident. Look for dead tip growth or twisted and distorted new growth. Also, we are seeing ivy geranium cuttings with thrips on the bottom side of the leaves on new cuttings. Get out your hand lens and inspect the cuttings when they arrive. Sticky cards need to be placed in your cuttings now to detect thrip numbers. Aphids are showing up in asparagus sprengeri that has been held under benches or off in a corner of the greenhouse. Be sure to treat these plants now to avoid spreading aphids around the range. Finally, two-spotted spidermites have been reported in a number of greenhouses hiding in the Dracena (spikes) that also are off in the corner or under the benches. Tap a few plants on a white piece of paper and see if you notice the tiny mites moving around. Get them under control now before moving them around in mixed containers later. As for the insecticides or miticides to use, I suggest you visit: www.ipm.msu.edu/grnhouse08/G12-01-07.htm#2 for recommendations from Dr. David Smitley on the best materials to use. An ounce of prevention through scouting and treating early on will make big dividends later in the year. |
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| Greenhouse*A*Syst: A free tool for growers Are you interested in determining how your greenhouse can identify pollution risks, reduce nutrient losses and protect water resources? Greenhouse*A*Syst is a free assessment tool that growers can use to help identify management practices that when implemented will reduce the impact of their operation on the environment. The production of greenhouse crops requires advanced technology and precise use of light, temperature, pesticides, fertilizers and water to produce high-quality garden and potted plants. Like other agricultural enterprises, floriculture involves a number of processes that can potentially affect surface and groundwater. Greenhouse*A*Syst was developed by MSU Extension educators to assist greenhouse growers to identify pollution risks and to make any needed improvements to protect water resources. It will also help growers become aware of applicable federal, state and local environmental regulations. Greenhouse*A*Syst is a series of risk questions that will help evaluate how effectively a producer’s greenhouse management practices protect groundwater and surface water resources. The risk questions are grouped into 14 sections including greenhouse site and soil evaluation; pesticide storage, handling, and worker safety; fertilizer storage and handling; nutrient and water management practices; and pest management practices. Producers who complete the Greenhouse*A*Syst assessment will be able to determine what structural, management practices or record-keeping changes (if any) will be needed for their businesses to be environmentally assured through the Michigan Agriculture Environmental Assurance Program (MAEAP). Owners of MAEAP-verified greenhouse systems are eligible for various incentives and can enjoy good-faith effort environmental liability protection if an agricultural pollution emergency ever occurs at their facility. To download this free tool, please visit the MSU Floriculture AoE Team website or download Greenhouse*A*Syst directly. Adobe Reader is required to view the document. |
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| Environmental assurance for greenhouse crop growers Is your greenhouse environmentally sound? Are you helping to foster positive community relations when the public views your facility? Is your buyer asking for “environmental certification” to show you are producing crops with minimal or no impact on the environment? Do you want to demonstrate to your neighbors, buyers and fellow greenhouse growers that you’re “environmentally sound?” See the brochure at: http://www.ipm.msu.edu/grnhouse08/pdf/growersflyer08.pdf If you answered yes to any one of the above questions then consider the Greenhouse MAEAP program (Michigan Agriculture Environmental Assurance Program). MSU Extension will be holding a short discussion on how a greenhouse grower can become MAEAP-verified on Friday, January 18. Plan to join fellow interested growers at: Henry Mast Greenhouse 2125 72nd Street S.W. (north range) Byron Center, MI 49315 Friday, January 18, 2008 10:00 AM to 12:00 PM MAEAP-verified farms are recognized across Michigan as outstanding environmental stewards and are eligible for cost-share incentives, tax credits, low cost lending and reduced insurance premiums from participating companies. The ability to have a nice sign out in front of your business saying your MAEAP verified is a plus as well. Hope to see you on January 18. |
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