Examination of the significance of sugarcane rust mite (Abacarus sacchari) on sugarcane

The sugarcane rust mite, Abacarus sacchari Channabasavanna (Actinedida: Eriophyidae), was discovered on sugarcane in Canal Point, FL in September 2007. Though first observed in Belle Glade, FL on sugarcane in 1983, it was originally identified as Abacarus officinari Keifer. Described from Asian specimens, A. sacchari has now been recorded from Africa, Australia, India, Costa Rica, Venezuela, Brazil and Florida. Feeding by these mites results in an orange to rusty reddish-brown to purple discoloration on the underside of leaves that was originally masked by an outbreak of orange rust, Puccinia kuehnii. The orange symptom color is similar to that of orange rust, but the A. sacchari feeding symptom is more uniformly distributed over the leaves and does not result in the raised pustules characteristic of rust. Damage symptoms are variety specific. Beyond the range in discoloration among varieties, symptoms can be restricted to the mid vein, leaf blade, or spread across the leaf surface by variety. Significant differences in photosynthetic components were observed between sugarcane with and without A. sacchari. Leaves damaged by mite feeding displayed reduced photosynthesis associated with reduced chlorophyll content, transpiration, and stomatal conductance, but elevated intercellular CO2 concentrations.