DEVELOPMENT AND EVALUATION OF A PRECISION HERBICIDE APPLICATOR FOR SPOT APPLICATION OF DICHLOBENIL TO CONTROL HAIR FESCUE IN WILD BLUEBERRY FIELDS

Abstract

Hair fescue (Festuca filiformis) is the pest of greatest concern for the Nova Scotian wild blueberry (Vaccinium angustifolium Ait.) industry given its rapid spread and lack of effective treatment options. Hair fescue has rapidly spread from 2001 when it was found in only 7% of wild blueberry fields to now having a presence in over 75% of fields throughout the province. Pronamide is currently the only widely employed treatment, making it vulnerable to herbicide resistance. Dichlobenil is a group 29 herbicide registered in wild blueberry though, it has had little implementation for managing hair fescue despite its labeled use for perennial grasses. This study began by exploring the effect of dichlobenil on hair fescue at three rates (4400, 5700, and 7000 g a.i. ha-1). Results demonstrate a similar treatment effectiveness to pronamide and produced significantly greater wild blueberry yields than pronamide at the highest label rate. The study then explored the effect of spot versus broadcast applying dichlobenil. It concluded that there were limited differences between the methods and that spot application could be an important option in reducing dichlobenil product costs which can be as high as $1800 ha-1. Once the efficacy of dichlobenil had been realized, the third study was to develop a precision spot applicator for granular agrochemical. This design retrofitted a Valmar 1255 Twin-Roller so that individual boom sections could be controlled based on the input from a predeveloped prescription map. Modifications included the development of custom valves for controlling product application, a custom control box for reading and sending control signals and various minor alterations to the blower fans, hosing, deflector plates and venturi. In field testing the system, it was determined that the novel applicator had an accuracy, precision, sensitivity, and specificity of 95%, 91%, 99%, and 91% respectively. With the system performing well, the final study calculated the economic benefits of the applicator. The analysis demonstrated that the system reduced per hectare application costs by 62.5% over broadcast application. This resulted in a breakeven point of 47.58 applied hectares after accounting for all costs related to the system.