Greenhouse Update - March 27, 2006
Leanne Pundt, Extension Educator, University of Connecticut
Iron deficiency symptoms are starting to appear on the usual suspects- calibrachoa, scaevola and vegetative petunias. Other crops that can develop iron chlorosis include brachychome daisies, argyranthemum, pansy, snapdragon and vinca.
Look for yellowing between the veins, (iron chlorosis) beginning on the youngest leaves. As symptoms progress, leaves turn completely yellow and even white. Yellowing of foliage may also occur due to low EC levels (lack of fertilizer), overwatering, root stresses due to fungus gnat feeding, root diseases, or cold media temperatures).
Keep the pH in the range of 5.5 to 6.0. At high pH, deficiencies of micronutrients – especially iron may occur, in crops that are inefficient in taking up iron. (Iron decreases in soluability at high pH)
In many cases, using an acid forming fertilizer such as 20-10-20 may be sufficient, especially if you do not have alkaline water.
Fertilizing crops with a more available form of iron (known as a iron chelate) such as Sprint 330 (10% Fe, releases up to pH of 7.0) or Sprint 138 (6% Fe, release up to pH of 9). (See label at: http://www.beckerunderwood.com/labels/sprint_138.html)
Apply as a soil drench (rate of 8 oz per 100 gal or ½ to ¾ tsp per gal). Keep in mind that a healthy root system is needed for the plants to take up the iron chelate.
Apply early in the morning so the chemicals do not dry on the foliage.
Immediately wash off the foliage to avoid any spotting of the foliage.
Iron chelates can be applied every 3 to 4 weeks
See How to Prevent Iron Deficiency in Spring Greenhouse Crops http://www.umass.edu/umext/floriculture/fact_sheets/greenhouse_management/irondef.html
See also Managing pH of Container Growing Media
Iron deficiency symptoms
Photos by Leanne Pundt
Lupine Anthracnose - Some varieties of lupine are very susceptible to Lupine anthracnose, caused by the fungus Colletotrichum gloeosporioides. On young seedlings, tips begin to die back like a shepherd's crook. Leaf blights that start with a half-circular brown spot at the edge of the leaf then develop into stem cankers. To help prevent lupine anthracnose:
· Avoid over-fertilization that promotes succulent, tender growth that is more susceptible to diseases.
· Avoid overhead irrigation and keep the foliage as dry as possible.
· Regularly scout young plants for the characteristic symptoms and rogue diseased plants promptly. If you start your plants from plugs produced elsewhere, look at lupines closely for symptoms, and rogue out symptomatic individuals before treating and transplanting the rest of the plugs.
· Apply fungicides such as Heritage, Compass or Cygnus, alternated with protectant fungicides such as mancozeb or chlorothalonil.
Photo by Leanne Pundt
Thrips, aphids and mites continue to appear on their favorite crops. See previous update of March 20, 2006 for more information.
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Previous 2006 UConn IPM Greenhouse Updates
|March 20, 2006|
|March 3, 2006|
|February 25, 2006|
|February 17, 2006|
|January 31, 2006|
|New England Greenhouse Update now online. University Extension Specialists in New England, in conjunction with USDA's Northeast Sustainable Agriculture Research and Education, contribute information to this new website. Timely updates are provided for commercial growers of greenhouse crops and flowers in Massachusetts, Connecticut and Rhode Island. You can use this additional resource for more information about current observations and recommendations on environmentally safe production practices.|
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