California Red Scale Workshop Provided Insights Into Scale Issues

On September 30, an in-depth workshop was held at the UC ANR Lindcove Research and Extension Center to discuss the biology and management of California red scale.  Twenty seven participants spent the day viewing scales under microscopes and learning about Aphytis and Comperiella wasps.  The hot topic (literally) this year, above and beyond the usual complexities of managing scale, was the much higher than average accumulation of heat units.  Normally there are about 4 generations of scale per year in the San Joaquin Valley, but this year a 5th generation is developing.  This is the third year in a row that temperatures have been above the 30 year average.  We also discussed the fact that systemic neonicotinoid insecticide use is becoming very common place and repeated use of the systemic neonicotinoids results in a build up of scale on the wood that is difficult to control with natural enemies or insecticides.  So, the combined problems of scale build up due to changes in insecticide use patterns and high average daily temperatures have resulted in outbreaks of California red scale in the San Joaquin Valley.