Evaluation of Foliar Miticides for Management of the Sugarcane Rust Mite in Sugarcane, 2017 Open Access

Sugarcane rust mite infestations have been detected in Florida sugarcane since 2007; however, no miticides have been registered for management purposes. In response to this need by the local sugarcane industry, the efficacy of miticides for control of the sugarcane rust mite in sugarcane was evaluated in a commercial field of variety ‘CPCL 05-1102’ (1st stubble) near Belle Glade, FL. Three foliar miticides and an untreated check were assessed in an RCB design with four blocks and one replicate of each treatment per block. Plots were four rows wide (5-ft row spacing) and 40 ft long with 10-ft alleys separating each plot. Prior to miticide application, 20 plants were randomly selected from the middle two rows and injury was recorded on the top visible dewlap (TVD) + 1 and TVD + 3 leaves. Because sugarcane rust mites are difficult to examine in the field, a visual symptomatic rating was developed for injury symptoms: (0) no discoloration of the leaf tissue, (1) light discoloration of <25% leaf tissue area, (2) moderate discoloration on 25–75% of leaf tissue area, and (3) >75% heavy discoloration throughout leaf tissue area. Miticide sprays were applied to the foliage on 18 Aug 2017 using a tractor propelled, high clearance four-row spray boom with 13 nozzles spaced 18 inches apart calibrated to deliver 10 gpa at 40 psi. Treatments were delivered to the boom using a pressurized system with portable CO₂ tanks. Injury was rated on a scale of 0–3 at 5, 12, and 19 DAT. Data were analyzed using linear mixed models (PROC GLIMMIX, SAS Institute) with treatment, sampling date, and the treatment by sampling date interaction as fixed effects. The SPLICE and SPLICEDIFF options were used to compare sugarcane rust mite injury ratings as affected by treatment on each date. Means were separated using Tukey’s HSD (α = 0.05).

Differences in sugarcane rust mite injury ratings were detected among treatments (F = 17.8, P < 0.001, Table 1) and sampling dates (F = 61.6, P ≤ 0.001). The treatment by sampling date interaction was also significant (F = 8.2, P < 0.001). Injury ratings pretreatment and 5 DAT did not differ (P > 0.05), ranging from 1.3 to 1.4, and 1.3 to 1.5, respectively. Plots treated with the three miticides exhibited reductions in leaf injury ratings compared with the untreated check. Injury ratings in the treated plots averaged 0.8 to 0.9 12 DAT and 0.5 to 0.6 19 DAT compared with 1.3–1.7 in the untreated check.

This research was partially supported by industry gifts including field sites and products.