Sex ratio dynamics of the field population of the sugarcane rust mite Abacarus sacchari (Acari: Eriophyidae)

Sugarcane in southern Florida suffers from sugarcane rust mite (SRM) infestations, Abacarus sacchari, from summer to early fall. The mite's sex ratio is important in understanding the mite's demography and population dynamics. This is the first report on the sex ratio of the field population of the SRM. The objectives of the study were to determine the sex ratio of the SRM and the factors that affect any changes in the sex ratio. To determine the sex ratio, mites were sampled from a sugarcane canopy each month over a 12-month period and the sex ratio was expressed as the proportion of females to the total number of sexed mites. The population density and aerial mites were monitored weekly for 8 and 6 months, respectively. The total number of sexed mites from the sugarcane canopy was 27 941 mites, while 2 248 airborne mites were recorded. The result showed that the sex ratio of the SRM in the canopy was dynamic during the study, with a female bias more common than a male bias among the samples, which ultimately resulted in a slightly female bias. An obvious change from a female bias to a male bias occurred simultaneously with the increased mite density and dispersal. The factors affecting the oscillation of the sex ratio are discussed.