April 29, 1992

Overwintered Wasps

Wasps such as yellowjackets and paper wasps seen at this time of the year are overwintering queens produced by colonies last fall. In the autumn they find refuge in protected sites in and around the home and landscape. The wasps that survive the winter are the fertilized "foundress" queens that will start "from scratch" to build a new nest and colony.

Diplodia Tip Blight

Now is the time to be taking measures to control Diplodia tip blight.

Suggested Pear and Stone Fruit Varieties for Home Gardens in Iowa

Pears and several stone fruits can be successfully grown in Iowa. Pears can be grown satisfactorily in most areas of the state. However, fireblight can be a serious problem. Gardeners should plant fireblight resistant pear varieties.

The stone fruits include cherries, plums, apricots, and peaches. Most stone fruits are relatively short-lived. Some stone fruits, such as apricots, bloom early in the spring and are often damaged by a last frost or freeze. Others, such as sweet cherries and peaches, are not reliably hardy in Iowa.

Is it Ground Ivy or Henbit?

A few calls and plant samples have come in during the past week on control of a broadleaf plant with roundish leaves and purple flowers. My first reaction is that this person has ground ivy, but I have seen a lot of henbit this spring which also looks like ground ivy.


Branch and twig samples showing lichen (pronounced "liken") growth often arrive at the Plant Disease Clinic to be diagnosed for disease. These interesting organisms, however, do not cause disease problems. They live and gather sunlight on twigs or branches but do not infect the tree. Many lichens grow rapidly when exposed to full sunlight, which explains their common occurrence on dead or dying trees. In addition to growing on tree parts, lichens can be found on dead wood, rocks, soil, tombstones, or other sunny places.

Care of the Easter Lily after Flowering

Now that the flowers of the Easter Lily have withered, many people are wondering what to do with the remaining plant. The lily doesn't survive as a houseplant, but it can be planted outdoors where it should bloom again. Until it is safe to plant outdoors, keep the plant in a sunny window and water thoroughly when slightly dry.

Determining Plant Quantity

Does your garden look as full and lush as you want it to? Are you envious of your neighbor's garden or the flower beds in the park down the street? The problem may be solved by simply planting the correct number of plants. Proper plant spacing is an important key to garden success. Following the recommended plant spacing requirements allows plants to develop fully and fill in the area properly. Proper spacing also prevents the invasion of weeds as well as allowing enough air movement between plants to prevent diseases.

Pine Sawfly Hatch Underway

Now is the time to begin watching pine trees for feeding damage by clusters of European pine sawfly larvae. These gray-green larvae with the shiny black beady heads are common on mugo, Scots and red pine, and may be found on other pine species as well (white and Austrian pines are usually only attacked if interplanted with the more susceptible species). The phenological indicator plants and their stage of development that coincide with the onset of European pine sawfly egg hatch and presence of small larvae are: