Extension News

Ask the ISU Garden Experts: Snap Beans, Orange Grass and Holes in Roses

Note to media editors: Got gardening questions? Call the Hortline at (515) 294-3108, Monday-Friday from 10 a.m. to noon and 1 to 4:30 p.m., or e-mail us at hortline@iastate.edu. For more gardening information, visit us at Yard and Garden Online, http://www.yardandgarden.extension.iastate.edu

7/16/2009

How late can I plant snap beans?

Snap beans are warm-season vegetables and should be planted after the danger of frost is past. In central Iowa, it’s usually safe to begin planting snap beans in early May. If harvested frequently, plants should produce well for several weeks. The last practical date for planting snap beans is Aug. 1.

The grass beneath one of my trees has turned brownish orange. Why?

Greenbug aphids may be responsible for the brownish orange color of the turfgrass. Greenbug aphids feed only on plants of the grass family (Kentucky bluegrass, corn, sorghum, etc.). Greenbugs live on the grass blades and feed on sap from the plant. As they feed they inject a toxin that causes an orange to brownish orange discoloration. Feeding damage is most severe and damage is usually first noticed in the shade beneath trees or shrubs and next to buildings.

Greenbug aphids are quite small, but can be seen with the naked eye. The aphids are typically found on blades of grass pulled from the outer edge of the discolored area. The aphids are light green in color. Forty or more aphids can be found on a single blade of grass.

Vigorous, healthy turfgrass is able to withstand some greenbug aphid feeding. Treatment may be necessary if the grass is stressed because of poor growing conditions or the brownish orange discoloration is extensive. Greenbug aphids can be controlled with insecticidal soap or chemical insecticides such as malathion. Spot treat only the infested area and a small buffer beyond.

There are round holes in the foliage of my roses. What is responsible for the damage?

Leafcutting bees are probably responsible for the holes in the rose foliage. Leafcutting bees resemble honey bees, but are often darker in color. Female leafcutting bees make nests in rotted wood or the stems of plants. The sides of the nesting cavities are lined with round pieces of foliage. After lining the cavities with leaf discs, pollen and nectar are placed in the nest cells to serve as food for the immature bees.

Leafcutting bees may remove discs of foliage from many plants. However, they prefer rose, green ash, redbud, lilac, and Virginia creeper. Holes in the leaves are typically one-half inch or less in diameter. The cuts are clean, as if they were “punched out” with a paper punch.

Leafcutting bees are beneficial pollinators. Damage to roses and other plants is usually minor. Control efforts are rarely justified or necessary.

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Contacts :

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

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