Thrips

Description:
For such tiny little bugs, thrips sure can do substantial damage. They are about 1/20 in. long and are difficult to see. They generally hide and feed in the buds of flowers and young foliage but may be found on the undersides of leaves. Thrips thrive during hot, dry weather; so, watch for them during summer months.

Damage:
Thrips are not gentle feeders. They tear at the plant tissue as they eat, scraping the chlorophyll away. Greenhouse thrips cause leaves to appear speckled or yellowed, much like mites do, but without the presence of webbing. Flower thrips are the most common species. They do their damage before the buds ever open causing the flowers to appear twisted, stunted, deformed, or to not open at all.

Prevention:
Thrips like things hot and dry so keep susceptible plants well watered and cool if possible. Some target plants include azaleas, roses, indoor plants, greenhouse plants, cacti, and annual flowers. Every so often rinse the leaves of these plants to discourage thrip populations.

Management:
Mild Infestations: Thrips are attracted to the color yellow and can be trapped on yellow sticky cards. You can buy traps or make you own using yellow posterboard coated with petroleum jelly. For edible plants, lightly sprinkle diatomaceous earth or garden sulfur on the undersides of foliage to kill thrips. For other plants, use insecticidal soap or horticultural oil. Always follow label directions.

Severe Infestations: When populations are high you can hit thrips with chemical pesticides. Acephate (Orthene) is an effective systemic against greenhouse (foliage feeding) thrips but not flower thrips. Systemics do not translocate to flower parts. Growers often add sugar to the pesticide solution, 1 pound sugar for 100 gallons of solution. The sugar is thought to entice the thrips from their hiding place, exposing them to the chemical. There is no solid proof this works, but it is a widely practiced method and it will not hurt the plants.