KAC Citrus Entomology
University of California
KAC Citrus Entomology

Insecticide Resistance Monitoring

Organophosphate and Carbamate Bioassay

Esterase test of scales
Scales that have resistance to the organophosphate (Lorsban, Supracide) and carbamate (Sevin) insecticides block those insecticides by producing more esterase enzymes.  We can measure the amount of esterase enzymes in their bodies using this colorimetric test.  The darker the color in the well, the more enzymes and the more resistance that scale has.  We use this to monitor for resistance.  Many populations of red scale in the San Joaquin Valley  have resistance to this group of insecticides. 

Esteem Resistance Bioassay

Esteem bioassay
To test for Esteem resistance, we circle the first instar scales and dip the fruit in a concentration of Esteem that should kill them all (10 ppm).  We are finding some sites with as much as 40% survival of that concentration, suggesting that resistance is starting to develop.

Contact Us for Esteem or Organophosphate Resistance Testing of your California Red Scale

The Citrus Entomology Lab is accepting samples of red scale-infested fruit for insecticide resistance assays.  We need a grocery bag full of scale-infested fruit (at least 50 pieces), a map of the location, and the pesticide history of the block to run the test.  This test is best done during July-October when the fruit is green.  If you have one or more orchards that you would like to have tested, please contact Greg Montez at 559-646-6597 or gregm@uckac.edu

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