April 23 2010 Greenhouse Update
Friday, 23 April 2010 09:35
Plants at many greenhouses appear to be a little ahead. If you are thinking about holding plants using growth regulators, review the message: Using Plant Growth Regulators to Hold Finished Plants. A proper hold rate using growth regulators should give enough control to hold a mature plant under hot weather for 2-3 weeks but low enough that the plant will recover and grow for the consumer. Spray treatments carry less of a risk of overdose than drench treatment, especially when the root-active PGRs are used.
Monitor for powdery mildew on gerberas. A good short video on the subject is available from Floricast by Margery Daughtery, Cornell University.
Spider mites continue to be a problem on crops such as ivy geraniums and mandevilla and on perennials such as salvia, monarda, nepeta and perovskia. Spider mite injury on ivy geraniums looks like oedema, so be sure to monitor carefully with a hand-lens. See photos of oedema vs spider mite damage.
See message: Managing Two-spotted spider mites
Spider mites are very successful at surviving over the winter in their resting stage. The can hibernate in any crevices in the greenhouse so growers having problems last year are likely to have problems this year.
Finally, when sunshine turns to clouds and rain, avoid wet foliage, reduce humidity by heating and venting and monitor for Botrytis. See messages: Heating and Venting and Botrytis
Leanne Pundt, University of Connecticut
Tina Smith, University of Massachusetts
