Upon hatching in spring, the small worms migrate to dahlias and bore into the lower stem. Keep the areas near the garden free of weeds and grasses, and remove or thoroughly cover plant material remaining in the garden in the fall. In severe problem areas it may be necessary to apply an insecticide to the lower stem and around the plant base weekly during June. Thrips are found in open flowers but also may damage opening buds if the insects are abundant. They are likely to be most troublesome if the weather is hot and dry.
Injured areas turn white and then dry up.
Buds become distorted. Products listed in this publication are for the convenience of the reader, and are not intended as an endorsement. Use all chemicals according to manufacturer's recommendations, and follow all safety precautions to prevent pollution, or damage to humans, plants and animals. Kenneth R. Bolen, Director of Cooperative Extension, University of Nebraska, Institute of Agriculture and Natural Resources.