May 6, 1992

Apple Scab and Fire Blight

These are the most serious disease problems on apple and crabapple statewide. Apple growers should have begun their fungicide spray schedule for scab control by the 1/4-inch green stage. On crabapple, scab control on highly scab-susceptible cultivars should begin at the pink or early bloom stage (this week in central Iowa), with sprays repeated twice more thereafter at intervals of 10-14 days.

Botrytis on Vinca

An unusual disease problem on vinca (periwinkle) arrived in the Plant Disease Clinic least week. Stems of young vinca seedlings in plugs developed water-soaked areas above the soil line, and the tops of these seedlings fell over at the water-soaked point. This description sounds superficially like classic damping-off, in which soil-inhabiting fungi such as Pythium attack the roots and lower stem of seedlings, causing withering and collapse. The difference is that these vinca showed no problems at the soil line or in the roots; the affected areas were an inch or more above the soil line.

Care of Spring-Flowering Bulbs after Bloom

Iowans have been enjoying the beauty of tulips, daffodils, and other spring- flowering bulbs for the past few weeks. Proper care through the remainder of the spring will help to insure repeat performances in succeeding years.

Carpenter Ants Active Now

Once again, it is a good spring for carpenter ants. Activity by these common, widespread and abundant ants is very noticeable in the springtime, as the wingless workers work (enlarge nests, forage for food, care for the larvae) and the winged swarmers swarm (fly off to start new colonies).

Cancellation of Dyrene Fungicide

Several weeks ago, Miles Inc. (known until 1992 as Mobay Corp.) notified EPA that it intends to voluntarily cancel registration of all its fungicide products containing the active ingredient anilazine. The reason the company cited was that the projected costs of re-registering anilazine products (as required under the FIFRA legislation) was too high to justify reregistration.

Mowing New Lawns

Mow newly seeded bluegrass lawns at a height of 2 inches as soon as grass becomes 3 inches tall. Frequent mowing at this height will encourage spreading and promote a thicker lawn. If the new grass is allowed to reach a height of 4 inches or more, set the mower blade as high as possible and promptly mow. Gradually reduce the height of the grass in later mowings.

This article originally appeared in the May 6, 1992 issue, p. 71.

Using "Ortho Home Orchard Spray" During the Bloom Period

With increased Federal regulation of pesticides, the range of pesticide products available to homeowners at retail outlets such as garden centers and nurseries is narrower than a few years ago. With fewer choices, it's especially critical that homeowners read the labels on these products with great care in order to avoid misuse.


Pansies (Viola x wittrockiana) are familiar to most gardeners. Their variety and versatility make them a welcome addition to borders, patio containers, hanging baskets, window boxes, and flower beds. Many people are attracted to the faces (blotches) common with many varieties. Non-blotched forms are also available. Color selection is another attractive feature. Pansies are available in every color of the rainbow. They offer some of the best shades of blue found in annual flowers. Most have color combinations of 2 or 3 different colors or various shades of the same color.

Blossom Removal On Strawberries

In order to establish a productive strawberry planting, proper care after planting is essential. During the first growing season, all the blossoms should be removed from June-bearing strawberries. If the berries are allowed to develop, they will reduce plant growth, runner production, and next year's crop. Check the plants once a week and remove the blossoms by pinching or cutting. Flower production should cease by early July.

Giant Water Bugs

One of the largest insects commonly encountered in Iowa is the giant water bug. These moderately common aquatic insects live in lakes, ponds and quiet streams, but they are strong fliers, they are attracted to lights, and consequently, often are found a considerable distance from water. They may be found in the yard or street under a street lamp, or they may have crawled by accident into the house or other building.

Weed Control in the Home Garden

There are three basic methods to control weeds in the home garden -- cultural methods (hoeing and hand weeding), the use of mulches, and application of herbicides.

Chemical weed control is an easy and effective way to control weeds in agricultural crops. Unfortunately, there are several problems involved when using these materials in the home garden.