Pests and Pest Control
Thrips are the tiny insects that scar our light colored rose petals with their annoying habit of scratching open the surface of cells and feeding on the cell contents. This results in brown edges on white petals and disfigurement on petals of all colors. I would rather hear fingernails on a blackboard. Even their name is annoying. Thrips is singular and plural. One annoying little insect is still a thrips; it is not a thrip! At least most irregular nouns have the decency not to end in an "s"
Thrips are relatively primitive insects, having incomplete metamorphosis and rasping-sucking mouthparts. Adult thrips have strange, feather-like wings that carry them from flower to flower where they feed on both pollen and plant sap, as described. The most commonly seen species in roses is the Western Flower Thrips, known in much of the world as the "California Curse" since we have exported this creature to most parts of this country and many of the countries around the world. In addition to its other bad characteristics, it spreads some important diseases; the most important of which is tomato spotted wilt virus. Fortunately this is not a problem in roses.
Once adult female thrips have ruined a potential Queen of Show, they lay their eggs in the damaged flower where they quickly hatch and add insult to injury. These young thrips look much like their parents except they are lighter in color and lack wings. Once they have completed their development in a week or so, they drop to the ground and complete their transformation into winged adults in the soil. The whole process from adult to adult can be completed in as few as 14 days in warm periods.
Thrips are not without a long list of enemies besides rosarians and other gardeners. A tiny black and white bug called a minute pirate bug, or Orius, finds thrips a delicacy and especially enjoys them raw, skewered on their needle-like mouthparts which they use to suck the thrips contents down before casting off the empty shell. Ladybugs, lacewings and big-eyed bugs are other general predators that feed on thrips. The thrips family does have one redeeming member, the Six-Spotted Thrips, a cannibal of the thrips world that will feed on their fellow Western Flower Thrips as well as two-spotted spider mites. These good guys are easily identified by the six distinct black spots, three on each wing.
To keep thrips from taking over the rose garden, the beneficial insects just mentioned usually need some help. One very important thing rosarians can do to reduce thrips populations is to remove spent blooms from the plant promptly and to destroy them along with the thrips inside. A covered trash can or sealed black plastic bag placed in the sun is a fitting end for these little devils. Insecticides such as Orthene® or Mavrik® are good at controlling thrips, as are a few others. If you use these products, do so with caution and read and follow label directions.
Once adult female thrips have ruined a potential Queen of Show, they lay their eggs in the damaged flower where they quickly hatch and add insult to injury. These young thrips look much like their parents except they are lighter in color and lack wings. Once they have completed their development in a week or so, they drop to the ground and complete their transformation into winged adults in the soil. The whole process from adult to adult can be completed in as few as 14 days in warm periods.
Thrips are not without a long list of enemies besides rosarians and other gardeners. A tiny black and white bug called a minute pirate bug, or Orius, finds thrips a delicacy and especially enjoys them raw, skewered on their needle-like mouthparts which they use to suck the thrips contents down before casting off the empty shell. Ladybugs, lacewings and big-eyed bugs are other general predators that feed on thrips. The thrips family does have one redeeming member, the Six-Spotted Thrips, a cannibal of the thrips world that will feed on their fellow Western Flower Thrips as well as two-spotted spider mites. These good guys are easily identified by the six distinct black spots, three on each wing.
To keep thrips from taking over the rose garden, the beneficial insects just mentioned usually need some help. One very important thing rosarians can do to reduce thrips populations is to remove spent blooms from the plant promptly and to destroy them along with the thrips inside. A covered trash can or sealed black plastic bag placed in the sun is a fitting end for these little devils. Insecticides such as Orthene® or Mavrik® are good at controlling thrips, as are a few others. If you use these products, do so with caution and read and follow label directions.
