UCONN IPM: Integrated Pest Management:Greenhouse Update

Aphids and mites continue to plague many growers. See previous updates for more detailed information.

Bacterial Leaf Spot disease has developed on certain varieties of Verbena. Don't confuse this disease with powdery mildew or with fungal leaf spot diseases. (See photo).

Bacterial Leaf Spot on Verbena
photo by L. Pundt
click for a larger image

Bacterial diseases tend to be more difficult to control than fungal diseases. Splashing water spreads most bacterial leaf spot diseases. Avoid overhead irrigation to help keep leaves dry. If certain plants are severely affected, one option is to toss those affected plants. Some growers have also been removing the most severely affected leaves. Then apply copper sprays such as Phyton 27 or Kocide. (See labels for information on plant safety and precautions).

Iron Deficiency symptoms are common on million belles, vegetative petunias, scalevola and certain varieties of torenia. Yellowing between the veins develops on the youngest leaves. (See photo). In advanced cases, the youngest leaves can become almost bleached white (See photo).


Symptoms of iron deficiency on vegetative petunia. Note yellowing between the veins. Photo by L. Pundt click for a larger image		Shoot tips can sometimes appear to be bleached white in severe cases. Photo by L. Pundt click for a larger image

Acid pH favors the availability of iron, so the desired pH for these sensitive crops is between 5.5 to 6.0. Often, using a commercial potting soil mix combined with acid-forming fertilizers such as 20-10-20 may be sufficient to keep the pH in the desired range. In addition:

Routinely check your media pH either by in house testing or sending samples to a commercial laboratory.
Routinely check your roots for any signs of root rot diseases, which would also affect nutrient uptake.
Routinely check greenhouse nighttime temperatures, especially on crops grown on the floor, as cold root zone temperatures would also affect the ability of the roots to function and take up nutrients.

Many growers use iron chelates on these sensitive crops. Sprint 138 (6% iron) is often preferred because of its ability to supply iron even at a high pH (9.0) or Sprint 330 (10% iron) can also be applied either as a drench or spray.

See labels at www.beckerunderwood.com

Spray Damage -- I have seen some cases of phyotoxicity or pesticide spray damage in my travels. (See photo).

Phytotoxicity or pesticide spray damage to Kalanchoe.
Photo by L. Pundt
click for a larger image

To prevent possible spray damage (critical now that many plants are in flower):

Read the label carefully before treatment for information on special precautions before use, information on plant safety, proper rates etc.
Go to www.cdms.net or www.greenbook.net to search for pesticide labels if you are having trouble reading your labels
If you are spraying small amounts of insecticides or fungicides (i.e. 1 gal or 25 gal), you can refer to the New England Greenhouse Floriculture Guide for smaller use rates.
To gather additional information, call your extension educator, the technical representative of the company, talk to other growers, etc, especially if you haven't used this product before.
Spot test a few plants for potential damage before treating your entire crop.
Apply pesticides in the cooler part of the day. Treatments made in the early morning will allow the foliage to dry before the temperatures reach 85-90^oF.
Never spray plants under drought stress. I have seen many pesticides considered to be very "safe" damage plants that were sprayed when the plants were wilting and the media was very dry.
Apply surfactants only when recommended on the pesticide label.
Avoid tank mixes. A mixture of several insecticides or several insecticides with a fungicide increases the risk of injury.
Never use more than one EC in a tank mixture
Do not apply pesticides with a fertilizer

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.

GREENHOUSE IPM COORDINATOR (commercial interests and growers)	LEANNE PUNDT	860-626-6240
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HOME GREENHOUSE QUESTIONS (homeowners)	UCONN HOME & GARDEN INFORMATION CENTER	phone toll free 1-877-486-6271 or email