Acaricidal Control of Citrus Rust Mite, 2017

Feeding by citrus rust mite (CRM) results in fruit russetting and bronzing that causes grade reduction in the fresh fruit market, and reduced juice yield and quality if injury is severe. This trial was conducted at the Southwest Florida Research and Education Center in Immokalee Florida on 6-yr-old ‘Hamlin’ orange trees grafted to US 802 root stock planted on double-row beds with a row spacing of 18 ft and a tree spacing of 8 ft (302 trees per acre). An RCB design was used to assign four replications of each of eight treatments and an untreated check to eight tree plots within rows separated by an untreated buffer row. Applications to both sides of the trees were made 8 Jun 2017 using a Durand Wayland AF100-32 air blast speed sprayer operating at 1.9 mph and 300 psi with three (4, 4, 4) John Beane Ceramic nozzles on each side to deliver 100 gpa. Two random fruit from each of six centrally located trees in each plot were sampled 1 day before treatment and then weekly from 13 Jun to 2 Aug, 5 to 55 DAT using a 14x Bausch & Lomb Hastings triplex hand lens. A ‘lens field’ of approximately 1.0 cm diameter was viewed on two partially shaded areas of each sampled fruit, and the mean number of mites per two lens field was reported. Data were subjected to ANOVA with means separated by LSD (P = 0.05).

CRM density prior to treatment averaged 8.65 mites per lens field. All treatments reduced the number of CRM found from 5 through 19 DAT (Table 1). At 19 DAT, CRM numbers on trees treated with Voliam Flexi, Harvanta, and Purespray were statistically lower than the untreated check, but not different from each other, indicating that the Voliam Flexi and Harvanta had not added to the activity of Purespray alone. A similar trend was seen at 33 DAT, so sampling in the Voliam Flexi and Harvanta plots discontinued. At 46 DAT, no further CRM suppression was noted on trees treated with Purespray alone, and fewer mites were seen on Minecto Pro trees compared with 5.5 oz rate of 3106 + AB, with the other rates not being statistically different from either the Minecto Pro or 5.5 oz rate. At 55 DAT, no treatment was different from the untreated and the trial was terminated.

No phytotoxicity was observed. This research was supported by industry gifts of pesticide and research funding.