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How to Manage Pests

UC Pest Management Guidelines


Chrysanthemum Leafminer

Scientific name: Chromatomyia (=Phytomyza) syngenesiae

(Reviewed 1/07, updated 6/09)

In this Guideline:


Adults are small black to gray flies with yellow markings. Females puncture leaves to feed on plant sap and lay eggs within the leaf tissues. After 2 to 4 days eggs hatch and larvae feed between the upper and lower surface of the leaves, making distinctive winding, whitish tunnels or mines that are often the first clue that leafminers are present. Larvae emerge from the mines and pupate on the leaf surface or, more commonly, in cracks in the soil. Many generations occur each year and the entire life cycle can be completed in less than 3 weeks when the weather is warm.


The primary damage caused by the chrysanthemum leafminer is the mining of the leaf by the larvae. When infestations are severe, the plant's photosynthetic capacity is reduced and there is a reduction in crop yield.


Chrysanthemum leafminer is usually kept in control by naturally occurring parasites and does not require any additional control efforts. All precautions should be taken to ensure that the parasites are not killed by pesticide sprays applied for other pests. In cases of severe infestation, a treatment may be warranted.

Biological Control
Biological control normally keeps leafminers in check, but outbreaks may occur following the disruption of their parasites with broad-spectrum insecticides. These leafminers are attacked and effectively controlled by an eulophid wasp (Chrysacharis ainsleii) as well as other species in the Diglyphus, Haltocoptera, and Opius genera.

Organically Acceptable Methods
Biological controls and sprays of the Entrust formulation of spinosad are acceptable for use on organically certified crops.

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 natural enemies and honey bees and to the environment. Not all registered pesticides are listed. Always read label of product being used.
CROP'S VEGETATIVE STAGE (from cut back through August)
  (Supracide) 25WP 4 lb 3 days see comments
  COMMENTS: Do not apply after buds begin to form. Do not exceed a total of 8 applications/crop cycle.
  (Entrust)# 1.5–3 oz 4 2
  (Success) 4.5–6 fl oz 4 2
  COMMENTS: Do not apply more than 7.5 oz of Entrust or 22.5 fl oz of success per acre/crop or make applications less than 7 days apart.
+ 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.
# 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). For additional information, see their Web site at http://www.irac-online.org/.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Artichoke
UC ANR Publication 3434
M. A. Bari, Artichoke Research Foundation, Salinas
E. T. Natwick, UC Cooperative Extension, Imperial County
Acknowledgment for contributions to Arthropods:
W. E. Chaney, UC Cooperative Extension, Monterey County
W. L. Schrader, UC Cooperative Extension, San Diego County
L. Handel and T. K. Shannon, Kleen Globe, Inc., Castroville, CA

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