Thrips are small, winged insects; some are benign, others feed on our landscape plants. Because thrips are particularly attracted to flower buds, they can hide inside and you won't be aware of an infestation until the plant begins to show symptoms. These symptoms include distorted leaves with brown scars and scarred petals. The best method of controlling thrips is the prompt removal of any infested parts of the plant.
Verbena, 'Tapien Lavender'
The International Society for Horticulture Science published a study in which four verbena cultivars were monitored for thrip infestation. The results of the study showed that the Western flower thrips preferred the Tapien Lavendar cultivar almost eight times more than the other three. If you are growing this cultivar of verbena, consider either moving it away from your other ornamentals and sacrifice it as a lure for the insect, or removing it from the garden altogether.
Petunias are another plant that is used by scientists in their efforts to find an effective control agent for the Western flower thrips. These insects are particularly attracted to the color blue, so the blue varieties of petunia, such as Super Blue Magic, Blue Carpet and Cascade Blue have a higher incidence of infestation.
Thrips are a common problem in the rose garden. The damage is cosmetic, and to a rosarian, that can be devastating. Roses are generally grown for their beauty and anything that mars that needs to be dealt with. Evidence of infestation includes buds that don't open or partially open and appear brown and nibbled on. Removal of infested areas of the plant is necessary. For more extensive control, contact your local cooperative extension for advice on what works well in your area.