Description of the Pest
Thrips are small, slender insects with mouthparts developed primarily for sucking and rasping. The adults measure about 0.04 inch (1 mm) in length and have two pairs of fringed wings, carried lengthwise over the back.
Damage
Western flower thrips is both a beneficial insect (it feeds on spider mites) and a pest (it can damage flowers and shoot tips during the early growth stages or occasionally, if populations are severe, immature fruit). Both the young and adults cause damage by rasping and puncturing surface cells. This results in a silvering, and sometimes deformation, of the leaves: edges of leaves tend to curl downward.
Management
Discing weeds before they flower can lessen attraction of the field to thrips. Do not disc after weeds have flowered, as thrips will move to crop plants. Monitor with yellow or blue sticky traps placed in field from seedling through flowering period to determine the magnitude of the thrips population. Be sure to determine that thrips-related damage is occurring and consider treating only if the population is causing serious damage to shoot tips, flowers, or fruit. Unnecessary treatments can cause spider mite buildup.
Organically Acceptable Methods
Weed management and sprays of the Entrust formulation of spinosad are acceptable in an organically certified crop.
| 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 the label of the product being used. | ||||
| A. | SPINETORAM | |||
| (Radiant SC) | 5–10 fl oz | 4 | 1–cucumbers 3–other cucurbits |
|
| MODE-OF-ACTION GROUP NUMBER1: 5 | ||||
| B. | SPINOSAD | |||
| (Entrust)# | 2–2.5 oz | 4 | 1–cucumbers 3–other cucurbits |
|
| (Success) | 6–8 fl oz | 4 | 1–cucumbers 3–other cucurbits | |
| MODE-OF-ACTION GROUP NUMBER1: 5 | ||||
| COMMENTS: Do not apply more than 0.45 lb a.i. spinosad/acre per season. Rotate with an insecticide that has a different mode of action. | ||||
| C. | METHOMYL* | |||
| (Lannate SP) | 0.5–1 lb | 48 | See comments | |
| (Lannate LV) | 1.5–3 pt | 48 | See comments | |
| MODE-OF-ACTION GROUP NUMBER1: 1A | ||||
| COMMENTS: For use on cucumbers, melons and summer squash only. PHI is 1 day when 0.5 lb or less for 90SP or 1.5 pt or less for LV formulations is used; when more than 0.5 lb (90SP) or 1.5 pt (LV) is used, PHI is 3 days. | ||||
| D. | DIMETHOATE | |||
| (Dimethoate) 2.67 EC | Melons: 1.5 pt | 48 | 3 | |
| Watermelons: 0.75–1.5 pt | 48 | 3 | ||
| (Dimethoate 400) 4EC | Melons: 1 pt | 48 | 3 | |
| Watermelons: 0.5–1 pt | 48 | 3 | ||
| MODE-OF-ACTION GROUP NUMBER1: 1B | ||||
| COMMENTS: Only labeled for use on melons and watermelons. Highly toxic to honey bees. | ||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) 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 two intervals is the minimum time that must elapse before harvest. |
| # | Acceptable for use on organically grown produce. |
| 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). |
| * | Permit required from county agricultural commissioner for purchase or use. |