The following are highlights and updates about samples and questions recently received in the Plant & Insect Diagnostic Clinic. Visit the PIDC’s Facebook page to ask questions and for updates and more pictures.
We've written before about "swarms" of dragonflies suddenly appearing in an area. See HHPN August 26, 2009 and HHPN August 25, 2010. Phone calls this week indicate they're back! We've had swarms in wet years and drought years, so it's not water level in the river that leads to so many. And it's not available food supply since this year there are almost no mosquitoes for them to eat. We still don't know why dragonflies congregate in some areas at certain times, but we do know to stop and enjoy the show when it happens. We hope you do too! For details on Iowa's dragonflies, see the Iowa Odonata Survey website.
Downy mildew on impatiens continues to be a problem. Watch impatiens for leaf drop that leaves bare stems. If it has been a problem in your landscape do not plant impatiens for 2-3 years.
Early fall color is very much in evidence around the state as trees begin to shut down prematurely because of the unfavorable conditions of the stressful summer. The problem is the environment and not plant diseases for the most part. Early fall coloration is particularly noticeable on maples, ash, birch and burning bush. Remember to be watering newly planted trees weekly. Water won't turn red leaves green again but it will aid the tree's overall health. Do not fertilize stressed plants in late summer. Read more in the Hort newsletter from July 11, 2012.