The prolonged cloudy cool weather in mid April resulted in issues with botrytis blight, downy mildew, and general nutrient deficiency symptoms as growers were not able to water (and feed) as much as usual. Iron deficiency symptoms were also noted. Adult shore flies and fungus gnats were noted, especially near areas with algae growth.
This situation changed this past weekend with record highs set in many locations. However, many greenhouse plants that prefer shaded locations were stressed in greenhouses without shade cloth in place. Plants may wilt rapidly even though the soil media is moist with a healthy root symptom.
Adult Shore flies may be seen near plants with algae growing on the media surface. Shore flies are primarily nuisance pests that feed upon algae. I have noticed higher populations in very humid houses with limited ventilation. Gradually moving the plants outside (depending upon the crop tolerance for cool night temperatures) will increase the air circulation around the plants, drying out the media and helping to discourage shore flies. Mass trapping of the adults with yellow sticky tape or large yellow cards may also help.
Some growers have tried low rates of insecticidal soap or Saf-T- Side horticultural oil, (avoiding known sensitive plants and those in bloom, and following all plant safety precautions) and spraying when adults are settled and you are more likely to contact them. Conserve may also work against shore flies. The long-term solution is to discourage algae on the surface of your growing media.
Nutrient deficiency symptoms have been observed especially on plants that are heavy feeders. With the change in weather, growers are able to feed and water more. See the NC State University Floriculture Deficiency Series for more information: http://www.ces.ncsu.edu/depts/hort/floriculture/def/
Iron deficiency symptoms have been appearing 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).
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
as needed.
See How to Prevent Iron Deficiency in
Spring Greenhouse Crops
Floriculture: Fact Sheets: Greenhouse Management: How to
Prevent Iron Deficiency in Spring
Greenhouse Crops
Spider mites, thrips and aphids continue to occur. See previous messages for more information.
| February 4, 2009 |
| March 23, 2009 |
| April 8, 2009 |
| 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. |
|
GREENHOUSE IPM COORDINATOR (commercial interests and growers) |
LEANNE PUNDT | 860-626-6240 |
| . | . | . |
|
HOME GREENHOUSE
QUESTIONS |
phone toll free |
Information on our site was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.
The information in this material is for educational purposes. The recommendations contained are based on the best available knowledge at the time of printing. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension system does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations as of the date of printing. If the information does not agree with current labeling, follow the label instructions. The label is the law.Warning! Agrochemicals/pesticides are dangerous. Read and follow all instructions and safety precautions on labels. Carefully handle and store agrochemicals/pesticides in originally labeled containers immediately in a safe manner and place. Contact the Connecticut Department of Environmental Protection for current regulations.The user of this information assumes all risks for personal injury or property damage.Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kirklyn M. Kerr, Director, Cooperative Extension System, The University of Connecticut, Storrs. The Connecticut Cooperative Extension System offers its programs to persons regardless of race, color, national origin, sex, age or disability and is an equal opportunity employer.