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California Red Scale Degree Days

California Red Scale Degree Days

2023 CRS degree day updates.

County DD as of November 15 Next life event CRS
Kern 4389 5th generation flight this week. 
Tulare 4478 5th generation male flight. 
Fresno 4117 4th generation crawlers have emerged.  
Madera 3757

Expect forth generation crawler emergence in coming weeks if the weather remains warm.

Pheromone traps are used to monitor California red scale (CRS) male flight activity. Following the biofix (first male flight) degree days (DD) are used to predict when the crawler emergence or when next generation flight takes place. Degree days for CRS are heat units accumulated above the lower developmental threshold (LDT) of CRS.

LDT for California red scale = 53 F

Degree days from Biofix to crawler emergence = 550 DD

Degree days for the second generation flight = 1100 DD

Degree Days for the second generation crawler = 1650 DD

Degree days for the 3rd generation flight = 2200 DD

Degree days for the third generation crawler = 2750 DD. 

Higher average daily temperatures mean faster accumulation of degree days, hence faster development of insects. 

This page updates current degree days for Kern, Tulare, Fresno, and Madera counties.

Low daily average temperatures in California during early spring has delayed CRS season in the valley. Biofix in all counties came ~4 weeks later (Biofix in earlier years has been March 1st week). Click here for an article. 

California red scale pest memos for 2023 season

May memo

July memo

End of the season memo