UC IPM: UC Management Guidelines for Thrips on Bermudagrass Seed Production

UC Pest Management Guidelines

Bermudagrass Seed Production

Thrips

Scientific Names: Chirothrips falsus and C. mexicanus

(Reviewed 1/07, updated 1/07)

In this Guideline:

Description of the pests
Damage
Management

DESCRIPTION OF THE PESTS

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/Acre

R.E.I.+

P.H.I.+

(trade name)

(hours)

(days)

When choosing a pesticide, consider information relating to the impact on natural enemies and honey bees and the environment.

ACEPHATE

(Orthene) 75S

1.33 lb

MODE OF ACTION: An organophosphate (Group 1B)¹ insecticide.

COMMENTS: Available for use under a 24(c) registration. Do not feed crop residue to livestock or allow animals to graze treated areas. Do not apply this product through any type of irrigation system.

Restricted entry interval (R.E.I.) is the number of hours from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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.

Modes of action are important in preventing the development of resistance to pesticides. 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. 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 is assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

UC IPM Pest Management Guidelines: Bermudagrass Seed Production
UC ANR Publication 3472
Insects and Mites
E. T. Natwick, UC Cooperative Extension, Imperial Co.
M. D. Rethwisch, UC Cooperative Extension, Riverside Co.

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