California red scale (CRS) development continues to run well ahead of normal across the San Joaquin Valley, creating a significant risk of missed treatment windows if management decisions rely solely on calendar dates.
Current Situation:
Current degree-day accumulations indicate that Kern, Tulare, and Fresno Counties have reached approximately 1,906, 1,924, and 1,633 DD, respectively. As a result, third-generation male flight is beginning this week in Kern and Tulare Counties, while second-generation crawler emergence is underway in Fresno County. Stay updated on current degree days at California Red Scale Degree Days | Lindcove Research and Extension Center
| County | Current Degree Days (DD) | Current CRS Life Stage | What you may find in field and recommended action |
|---|---|---|---|
| Kern | 1,906 DD | Third-generation male flight beginning | All life stages present/overlapping 2nd and 3rd generation. Check pheromone traps to confirm peak flight. Use DD models to predict third generation crawler emergence time insecticide applications accordingly. |
| Tulare | 1,924 DD | Third-generation male flight beginning | Check pheromone traps to confirm peak flight. Use DD models to predict third generation crawler emergence time insecticide applications accordingly. |
| Fresno | 1,633 DD | Second-generation crawler emergence underway | Monitor crawler activity closely using double-sided tape or twig inspections. Target susceptible crawler stage if treatment thresholds are reached. Continue monitoring for transition into third-generation flight. |
This season remains substantially ahead of both recent years and long-term historical averages. Warm spring temperatures accelerated CRS development, and every generation to date has occurred earlier than expected. If current summer temperatures persist, the fourth generation may begin by August or early September, potentially allowing CRS populations to complete a fifth generation in the San Joaquin Valley, an occurrence not previously documented under typical conditions.
Management Considerations:
Do not rely on traditional calendar-based application schedules this season. Instead:
- Monitor pheromone trap activity regularly, use DD models for predicting crawler emergence and confirm by sampling for white spots or crawler tapes.
- Prioritize scouting in known hotspot blocks.
- Align treatment timing with field observations and degree-day models. For treatment guidelines visit California Red Scale and Yellow Scale / Citrus / Agriculture: Pest Management Guidelines / UC Statewide IPM Program (UC IPM)
Timely Action Matters:
Missing crawler emergence periods can reduce treatment efficacy and allow populations to build rapidly during summer. With the possibility of an additional generation this year, effective monitoring and timely decision-making will be critical to maintaining season-long control. Stay vigilant, 2026 is proving to be an unprecedented CRS year.