Keep an eye out for potential problems in your greenhouse

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Over the last week, I have visited a number of greenhouses and noticed a number of issues going on or the potential for these situations to occur. The following educational items are provided from Tina Smith University of Massachusetts and should be helpful to growers in Michigan. If you suspect any of these problems, feel free to contact your local MSU Extension Greenhouse educator to confirm the diagnosis your making.

Edema on Cleome ‘Lady Armstrong’

Edema is a physiological condition caused by an imbalance of the plant’s water uptake and water loss. It develops when the plants roots absorb water at a faster rate than it is transpired through the leaf cells. The enlarged leaf cells divide, and then rupture. This rupturing of the leaf epidermis and inner cells causes the raised blisters commonly seen on the underside of leaves.
Read “Managing Edema on Spring Crops” factsheet from the University of Massachusettes.

Impatiens showing stress grown in greenhouse

A week of very high temperatures and sunshine the first week of May caught growers off guard. No shade cloth on the greenhouse.

Phytotoxicity due to the pesticide Judo

Leaf twisting, distortion, chlorosis and spotting (seen here on ivy geranium) can be caused by improper use of the pesticide Judo. These plants are growing out of the injury and new growth is normal. Judo is an insecticide and miticide labeled for mites and whiteflies. It is currently being used by growers to manage Q-strain biotype whiteflies on poinsettias. According to the Judo Technical Bulletin, Judo is not recommended for use on geraniums and other spring crops and tropical foliage plants. For details on preventing injury and for a list of crops, follow label directions and see the company’s technical bulletin.

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