Description of the Pest
Thrips may be abundant on bermudagrass florets and leaves. Adult Chirothrips are small, black insects about 0.04 inch long with two pairs of narrow wings that are fringed with hairs. Immature thrips are wingless and whitish to yellowish in color. To distinguish these thrips from beneficial thrips species, use a hand lens. Beneficial thrips include the western flower thrips, Frankliniella occidentalis, which is a larger insect than the Chirothrips spp. and varies in color from clear yellow to a dusky yellowish brown with darker pigmented areas on the segments of the abdomen. Another beneficial thrips, sixspotted thrips, Scolothrips sexmaculatus, has dark spots on its light-colored wings.
Chirothrips adults emerge continuously throughout the warm months. Adults and immatures may be found in bermudagrass at any time during spring and fall seed-production seasons. Eggs are deposited in plant tissue and hatching occurs in about 5 days; the immature stages take about 5 to 7 days to complete development.
Damage
Thrips are most noticeable and of greatest concern during spring and fall seed-production seasons when plants are in bloom. Their feeding in florets can reduce seed set.
Management
Good weed management in and around bermudagrass fields as well as along ditchbanks and roadways will help to keep thrips populations from building up. Monitor seed fields for thrips when florets are developing and continue through the seed set period. No threshold is established, but treat when thrips buildup is observed.
| Common name | Amount per acre | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide’s properties and application timing. Always read label of product being used. | ||||
| A. | ZETA-CYPERMETHRIN* | |||
| (Mustang) | 3-4.3 oz | 12 | 7 | |
| MODE OF ACTION GROUP NUMBER1: 3 | ||||
| COMMENTS: Efficacy trials pending, but experience with similar products has shown pyrethrins to be effective. | ||||
| B. | CYFLUTHRIN* | |||
| (Baythroid XL) | 2.6-2.8 oz | 12 | 0 | |
| MODE OF ACTION GROUP NUMBER1: 3 | ||||
| COMMENTS: Efficacy trials pending, but experience with similar products has shown pyrethrins to be effective. | ||||
| ‡ | Restricted entry interval (REI) is the number of hours from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest. |
| * | Permit required from county agricultural commissioner for purchase or use. |
| 1 | Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). |