May 11, 2010 Update
Tuesday, 11 May 2010 12:11
Weather related problems were observed over this past week. Paper thin brown spots - sunscald (many crops) caused by sun and wind, wilted new growth (basil) caused by chilling injury and silver color foliage (bacopa) were just a few of the symptoms observed. Shade perennials placed in full sun in both retail and grower locations resulted in sunburned foliage. Continue to watch weather reports over the next week. Cover plants at night, protect plants from the wind. Gradually expose plants grown in the greenhouse to cool temperatures.
Late season thrips and Impatiens necrotic spot virus were observed on plants this week.
Many growers used biological control for aphids and other pests this season. There has been confusion over identification of aphid mummies versus healthy aphids at retail locations. See photos of black aphid mummies and brown aphid mummies, many on a leaf.
Monitor for Rhizoctonia web blight on impatiens, herbs and other plants encouraged by dense canopies, closely spaced plants and humid conditions. Rhizoctonia is more commonly known as a fungus that causes root rot diseases. It may grow up from the media causing web blight during favorable environmental conditions. Stems and leaves collapse, with fine, web-like mycelium present. If you look closely, you can see the fine strands of the fungus. If there are certain houses or locations where you have seen outbreaks of Rhizoctonia web blight, consider growing crops that form a less dense canopy in those locations. Web blight can occur in the some locations and on the same crops year after year. Many of the fungicides labeled for Rhizoctonia root rot may also be helpful in limiting web blight. Rhizoctonia is a natural inhabitant of the soil and can survive there indefinitely.
Leanne Pundt, University of Connecticut
Tina Smith, University of Massachusetts
