A common insect found on seedlings is the thrip (Order Thysanoptera). Don't be deceived by appearances. Though these tiny yellow insects are about the size of an apostrophe, they can cause heavy physical damage to your plants and transmit viruses. The easiest way to manage thrips is to keep them from getting into your plants in the first place. This means checking any plants that you bring home carefully for signs of thrips. To check for thrips, carefully check the underside of the leaves, a tiny (approximately the size of an ",") yellow or brownish slender insect without visible legs or wings. Thrips prefer young, soft tissue and flowers. Pollen is a favorite treat, but they are also found along vein ridges. Even if you see only a single thrip, be sure to treat all the plants in the flat. For every thrip you see there are at least a dozen you don't.
|Thrip damage on potato leaves. Notice a group of yellow thrips circled in red.|
If no thrips are visible you can also look for thrip damage. Thrips have sucking mouthparts; they pierce the leaf and suck out all the juices in a cell. This will cause leaf cells to die, making young leaves grow in funny shapes and older leaves to have brown patches with a speckled appearance.
|A young misshapen pepper leaf. The thrip damage has killed the cell at the end (red circle) and the leaf can't expand properly.|
To treat for thrips you can use biological controls, such as the predator mites found in Thripex (http://www.koppert.com/pests/thrips/), insecticides, a simple soap solution. If you use soap be sure to douse the plant (preferably dip them in a bucket) to make sure that all the nooks and crannies in the plant have been treated. If you'd like to know more about thrips or insecticides you can use? Check out this information sheet from UC Davis: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7429.html
|Thrip on pepper flower.|