Damage to spinach by the crown mite—Tyrophagus dimidiatus (Hermann) — was first observed to be of economic importance during the spring of 1949 in the Santa Clara Valley. Since that outbreak the mite has caused periodic damage to fall and spring planted spinach in most areas, but is more destructive in the coastal growing regions.

The above progress report is based on Research Project No. 1275-G2.

The mites mentioned in the above report were identified by Dr. F. M. Summers, Entomology Department, University of California, Davis; Dr. H. H. J. Nesbitt, Carleton College, Ontario, Canada; and Dr. E. W. Baker, U. S. Department of Agriculture, Washington, D.C.