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How to Manage Pests

UC Pest Management Guidelines


Western spotted cucumber beetle.

Dry Beans

Cucumber Beetles

Scientific names:
Western spotted cucumber beetle: Diabrotica undecimpunctata undecimpunctata
Western striped cucumber beetle: Acalymma trivittatum

(Reviewed 8/07, updated 12/08)

In this Guideline:


DESCRIPTION OF THE PESTS

Cucumber beetles are frequently abundant in bean/pea fields, but damage is usually insignificant. The western spotted cucumber beetle is green, 0.25 inch long, and has eleven black spots on its wing covers. The whitish worm-like larvae feed on roots of corn and sweet pea as well as on grasses. When surrounding areas dry up, adults swarm into the field. A close relative, the western striped cucumber beetle, is yellowish and has three black lines down its back. The larvae live in the soil where they feed on roots, but adults are foliage and flower feeders.

DAMAGE

Cucumber beetles defoliate bean foliage and may damage bean flowers and buds.

MANAGEMENT

Specific treatment thresholds have not been established for these foliage feeders. Start inspecting plants for cucumber beetle damage along with other pests and their damage when the crop emerges. Continue looking through the vegetative growth and flower bud to bloom period. Late-season infestations are insignificant. If damaging numbers are encountered during mid-season and excessive foliage loss may reduce crop production, a treatment may be warranted.

Common name Amount/Acre** R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
When choosing a pesticide, consider information relating to the impact on natural enemies and honey bees and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. CARBARYL*
  (Sevin) 80S 1.25 lb 12 see comments
  (XLR PLUS) 1 qt 12 see comments
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: May result in outbreak of spider mites. Do not use on lentils in California. XLR Plus formulation is the least toxic to honey bees when direct application to bees is avoided and the spray residues have dried. Apply from late evening to early morning when bees are not foraging. Do not apply within 14 days of grazing or harvest for forage, within 3 days of harvest of fresh beans or peas, and within 21 days of harvest of dried beans, peas, seed, or hay.
 
B. MALATHION Label rates see label see label
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Highly toxic to honey bees. Do not apply when bees are present.
 
** Mix with sufficient water to obtain full coverage.
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) 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 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). For additional information, see their Web site at http://www.irac-online.org/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Dry Beans
UC ANR Publication 3446
Insects and Mites
L. D. Godfrey, Entomology, UC Davis
R. F. Long, UC Cooperative Extension, Yolo County

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