Deposition aids, nozzle selection and carrier volume on canopy deposition and management of Cercospora leaf spot in sugarbeet (Beta vulgaris L.)

Abstract

Cercospora leaf spot (CLS; Cercospora beticola Sacc.) is an economically devastating disease of sugarbeet (Beta vulgaris L.) in many regions worldwide. Field experiments evaluated the potential of InterLock deposition aid (MVO) and carrier volumes of 115, 235, 350, and 470 L ha−1 for improved CLS management with mancozeb (Manzate Pro-Stick) under moderate CLS intensity. Adding MVO to mancozeb did not reduce disease accumulation or improve yield or sugar quality more than mancozeb alone. Increased carrier volume did not affect disease progression but had a neutral effect on profit margin. Additional field experiments investigated the effect of MVO on spray deposition by analyzing Rhodamine WT recovery from leaves. Using MVO with mancozeb did not improve canopy deposition compared to mancozeb alone, regardless of the nozzle or carrier volume tested. Canopy deposition was improved using Hardi® ISO injet™ nozzles compared to Teejet® XR110 and Teejet® AI3070® nozzles. A quadratic relationship between dye recovery and carrier volume (R2 = 0.2871 p=<0.0001) was found; applications using a carrier volume of 350 L ha−1 improved deposition compared to 115 and 235 L ha−1. While MVO did not improve CLS management when mixed with Manzate Pro-Stick, nozzle selection did influence canopy deposition, and effects on CLS development require further investigation. In this study, increased carrier volume was not beneficial in limiting disease progress but incurred no economic penalty. Given the generally positive correlation between fungicide efficacy and the quality/degree of spray coverage, increased carrier volume should still be considered a best practice in disease management at the carrier volumes tested.