Controlling Thrips

By John Hefner

Thrips are very active, slender, brownish-yellow insects that upon closer examination appear to be tiny, hopping, wood splinters inside the buds and blooms of roses.  Thrips have rasping and piercing-sucking mouthparts.  They rasp the cells causing a wound which oozes sap. The thrips then draw the juices from the damaged cells.

Their life cycle is dependent upon temperature. In cooler temperatures, the life cycle can be a month; in warmer temperatures, it may take as little as fourteen (14) days.  They hide inside the unfurling buds and the resulting damage may make it impossible for the bloom to open beyond the bud stage.

Upon observation, you will notice the edges of light-colored roses turning brown since they seem to favor lighter colored roses.  They may be present in darker colored roses but they are more difficult to detect.  Since they are capable of flying, they are easily transported by wind and other garden chores such as cutting grass.

Since control is difficult, diligence will be necessary to be effective.  Some controls  will be more effective than others depending on the methods used.  It may be helpful to eliminate hosts by removing weeds and debris from the beds and other surrounding areas.  Removing damaged buds and blooms may partially provide control, however, to control them an insecticide seems to be the best alternative.  For years, the preferred method was to mist the blooms daily with Orthene, however, unless care is used, beneficial insects may also be eliminated.

Newer control insecticides called “biologicals” have proven to be more effective and ecologically friendly.  Conserve SC and Botanigard, both “biologicals”, target insects with either fungal or bacterial action.  The insects are infected and spread the infection to eggs and other members of the population.

Since control is difficult, my suggestion is to choose a program that provides each rosarian within the comfort level desired. There are many related searches that will provide additional information.