Air-blast sprayers are routinely used to apply pesticides in commercial peach orchards, with growers using both conventional air-blast and ultrasonic sensor driven models. Even with advanced spray technologies, there are still concerns with the amount of chemicals used and lost to drift. Our study evaluated a LIDAR-based variable rate sprayer system in three experimental peach orchards for pest and brown rot disease control, spray volume output, spray coverage, and spray drift. A single 378 L air-blast sprayer was used for both , the conventional air-blast and the Intelligent Sprayer (iSprayer) treatments. Treatments were started at the phenological stage of bloom and continued through final swell. The iSprayer treatment was as effective in controlling pests and brown rot disease as the conventional air-blast treatment. Compared to the conventional air-blast treatment, the iSprayer treatment reduced the spray volume (liter/hectare) in cultivar ‘PF23’ by 71% at bloom, 62% at pit hardening and 55% at final swell, respectively. For ‘Juneprince’ the spray volume reduction was 50% at bloom, 40% at pit hardening, and 13% at final swell, respectively. Spray drift was significantly (P<0.05) reduced only at bloom in the iSprayer treatment. Spray coverage was increased by 50.13% and 26.67% in the iSprayer treatment at bloom and pit hardening, respectively, but not at final swell. Our results show that the iSprayer maintained pest and disease control efficacy in peach orchards, while reducing spray volume and drift compared to the conventional air-blast treatment.

In this study, we investigated whether fungicide-induced mutagenesis previously reported in Monilinia fructicola could accelerate genetic changes in field populations. Azoxystrobin and propiconazole were applied to nectarine trees at weekly intervals for approximately 3 months between bloom and harvest in both 2013 and 2014. Fungicides were applied at half-label rate to allow recovery of isolates and to increase chances of sublethal dose exposure. One block was left unsprayed as a control. In total, 608 single-spore isolates were obtained from blighted blossoms, cankers, and fruit to investigate phenotypic (fungicide resistance) and genotypic (simple-sequence repeat [SSR] loci and gene region) changes. In both years, populations from fungicide-treated and untreated fruit were not statistically different in haploid gene diversity (P = 0.775 for 2013 and P = 0.938 for 2014), allele number (P = 0.876 for 2013 and P = 0.406 for 2014), and effective allele number (P = 0.861 for 2013 and P = 0.814 for 2014). Isolates from blossoms and corresponding cankers of fungicide treatments revealed no changes in SSR analysis or evidence for induced Mftc1 transposon translocation. No indirect evidence for increased genetic diversity in the form of emergence of reduced sensitivity to azoxystrobin, propiconazole, iprodione, and cyprodinil was detected. High levels of population diversity in all treatments provided evidence for sexual recombination of this pathogen in the field, despite apparent absence of apothecia in the orchard. Our results indicate that fungicide-induced, genetic changes may not occur or not occur as readily in field populations as they do under continuous exposure to sublethal doses in vitro.

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