Extension News

Ask the ISU Extension Gardening Experts

Note to media editors: Got gardening questions? Contact the Iowa State University Extension Hortline at (515) 294-3108 (Monday-Friday; 10 a.m.-12 noon and 1-4:30 p.m.) or send an e-mail to hortline@iastate.edu. For more gardening information visit us at Yard and Garden Online at www.yardandgarden.extension.iastate.edu.


Why are the leaves of my serviceberry turning brown?


The browning of the serviceberry (Amelanchier spp.) leaves is probably due to the hawthorn lace bug. Lace bugs are sap feeding insects commonly found on the leaves of shade and ornamental trees in Iowa. Trees most commonly affected are hackberry, sycamore, and oak. Adult lace bugs have attractive wings that are beautifully sculptured with an intricate pattern of veins resembling lace, hence the common name.


Lace bugs feed on the underside of the leaves. They pierce the leaf epidermis with their sucking mouthparts and cause the characteristic pale yellow, scorched or “bleached” discoloration on the upper leaf surfaces. The underside of heavily infested leaves will be speckled with small, black, shiny "varnish spots" (excrement). While lace bugs are present throughout the summer, damage symptoms usually don’t develop until August or September.


Lace bug damage varies greatly from year to year, mainly in response to variations in natural controls and weather conditions. Severe feeding may cause premature leaf drop, but healthy, well-established trees are not seriously harmed. Spraying infested trees with an insecticide in late summer is of little or no benefit to the trees. Further, spraying when it is too late for effective control may cause more harm than good by killing the insect’s natural enemies such as predators and parasites.


There are some small areas in my lawn where the grass is rather sparse. How do I fix these spots?


Thin spots can be repaired by overseeding. Overseeding is the sowing of grass seed into an existing lawn. In Iowa, late summer (late August to mid-September) is the best time to overseed a lawn.


Good site preparation is necessary for successful overseeding. Small areas can be prepared by gently raking the thin spots. The objective is to break the soil surface without pulling out the existing turfgrass. After raking, sow the seed by hand. Then work the seed into the soil by gently raking the areas a second time. To encourage germination, keep the seedbed moist with frequent, light applications of water. It’s usually necessary to water at least once a day. The grass seed should germinate within two to three weeks.


Can arborvitae be successfully grown in shady areas?


Arborvitae can be successfully grown in full sun to partial shade. Partially shaded sites are typically defined as areas that receive three to four hours of direct sunlight. Arborvitae tend to become quite loose and open in locations that receive less than three hours of sunlight.



Contacts :

Richard Jauron, Horticulture, (515) 294-1871, rjauron@iastate.edu

Del Marks, Extension Communications and External Relations, (515) 294-9807, delmarks@iastate.edu