California red scale season has started in the SJV.

Mar 13, 2024

Based on traps placed at LREC citrus blocks, California red scale season began with Biofix on March 10. Pest Control Advisors in Kern, Tulare, and Fresno County reported that they have seen activity, but the numbers have been low. If you haven't caught fliers on the traps yet, you are likely to catch some this week.

CRS Male

Figure. CRS male. Note the CRS has feathery antennae and a brown band through the waist.

What is CRS Biofix?

CRS Biofix is the start of California red scale activity for this season. As weather warms up and heat units are accumulated above the lower developmental threshold of this insects, overwintering females start producing crawlers which develop. Males' complete development and fly to find third instar females to mate. Mated females then produce crawlers which is the First Generation of Crawlers, observed 550-degree days after the biofix.

 What do males on the trap cards mean for management?

Pest control advisors have long used pheromone cards to monitor males and degree days to predict successive life event (crawler emergence) for timely management of CRS. Trap numbers may be different depending on the management choice.


CRS pheromone trap

Figure. 2. Pheromone card. To estimate number of males/trap, count the insects inside square boxes and multiply by 5. 

 IGRs and mating disruption – few male scales on the card as these options affect males more than it does females. You may have lower males on card but have high CRS populations.

    • Aphytis and Movento – Aphytis targets third instar females, thus affecting females more than it does to males. Also, Movento controls CRS on twigs but not on wood. If Aphytis or Movento or both are used, you may see higher males. If Movento was used, check the inner canopy branches, top of the tree for CRS patches.


Citrus entomology group will monitor degree days for four counties and update it biweekly on ucanr website

Stay tuned for updates.

By Sandipa Gautam
Author - Cooperative Extension Area Citrus IPM Advisor