Annuals, Perennials, and Bulbs: Thrips

Problem
Flower buds turn brown and die before they open. There are often silvery white streaks on the leaves. Flowers that have opened are often streaked and distorted. If the flower buds are peeled open, tiny (1/20 inch) insects resembling brown or straw-colored wood slivers can be seen moving around at the base of the petals.

Analysis
Several species of this common insect pest attack garden flowers. Thrips are found in protected parts of the plant, such as the insides of flower buds, where they feed by rasping the soft plant tissue, then suck the released plant sap. The injured tissue dies and turns white or brown, causing the characteristic streaking of the leaves and flowers. Because thrips migrate long distances on wind currents, they can quickly infest widespread areas. In cold climates, thrips feed and reproduce from spring until fall. With the onset of freezing weather, they find sheltered areas such as grass clumps and hibernate through the winter. In warm-weather climates, thrips feed and reproduce all year. These pests reach their population peak in late spring to midsummer. They are especially troublesome during prolonged dry spells.

Solution
Thrips cannot be eliminated completely, but they can be kept under control. Spray infested plants with an insecticide containing acephate. Spray 2 or 3 times at intervals of 10 days as soon as damage is noticed. Make sure your plant is listed on the product label. Repeat the spray if reinfestation occurs. Pick off and destroy old, infested flowers.