Infection of the Citrus Red Mite with Virus in Central and Southern California123

Abstract

Fifty-one citrus groves in 9 counties were sampled at regular intervals from February 1966 to May 1967 to determine populations of Panonychus citri (McGregor) and the presence of a noninclusion virus to which it is subject. Diseased mites were found on navel and Valencia oranges, lemon, grapefruit, mandarin, and lime. Incidence of the virus was noticeably higher in samples from central California than from other districts. High incidence of the disease was correlated with high density of mites. Invariably, epizootics succeeded large populations. Collecting mites with a vacuum insect net from groves of continuously low population revealed light infections in a large percentage of samples. Diseased mites were found in 82% of the groves sampled by this method and by brushing mites from leaf samples. Data suggested that the virus is in an occult state until conditions are suitable for infection. Three methods of diagnosing infection were used simultaneously, but none of them revealed infection in all populations; thus, better diagnostic criteria are needed.