In commercial fruit farms and ornamental tree nurseries, producers generally use integrated pest management tactics, including pesticide treatments, to control a variety of insect and plant disease pests (Beckerman, 2018; Braman et al., 2015). Pesticide applications are still a primary approach to ensure the yield and quality of fruits and ornamental plants (UMass Extension, 2018; Zhu et al., 2011a). For fruit production in the Midwestern United States, apple and peach need to be sprayed more than 10 times during the growing season, while blueberry and black raspberry need to be sprayed five to seven times, according to the Midwest Fruit Pest Management Guide (Beckerman, 2018). For apple production alone, 7.28 to 10.05 million pounds of pesticide active ingredients were used annually during 1990 to 2008 (Fernandez-Cornejo et al., 2014). In 2009, a total of 3.89 million pounds of pesticide active ingredients were applied on nursery and floriculture crops in California, Florida, Michigan, Oregon, Pennsylvania, and Texas (U.S. Department of Agriculture/National Agricultural Statistics Service, 2011).
In the United States, codling moth (Cydia pomonella) is the most serious pest in apple fruit (Beckerman, 2018), and oriental fruit moth (Grapholita molesta) is one of the most damaging pests in peach fruit (Brunner and Rice, 1993). Spotted wing drosophila (Drosophila suzukii) has been a serious pest of blueberry and black raspberry over the past 10 years (Fulcher et al., 2015). Potato leafhopper (Empoasca fabae) is a severe pest of maple trees in the Eastern United States (Frank et al., 2013). Aphids, including several genera, are one of the insects feeding on birch in Ohio (Division of Forestry, Ohio Department of Natural Resources, 2018). Insecticide treatments are the primary method for controlling these insect pests.
Apple scab (Venturia inaequalis) is a serious disease of apple and crabapple worldwide, leading to the greatest loss in apple yield among the apple diseases (Ellis, 2008). Powdery mildews are common foliar diseases on apple, peach, and dogwood trees (Blake et al., 2016; Ellis, 2016a; Witte et al., 2000). Brown rot (Monilinia fructicola) is the most serious disease for peach under warm and humid conditions (Hartman, 2007). Mummy berry (Monilinia vaccinia-corymbosi) is one of the most serious fruit diseases, and phomopsis (Phomopsis vaccinii) is the most common canker disease for blueberry (Anco and Ellis, 2011; Fulcher et al., 2015). Anthracnose (Elsinoe veneta) is an extremely serious disease of black raspberry in the United States (Ellis, 2016b). Treatments of fungicides are the primary tactics for controlling these diseases.
For applying pesticides on fruit farms and ornamental nurseries, the most used spray equipment are radial air-assisted sprayers (Zhu et al., 2017). These sprayers deliver pesticides at a constant rate, and they are usually configured and operated to apply pesticides to the entire field regardless of the absence of plants in rows, plant structure conditions, and plant growth stage, resulting in plants being under- or over-sprayed (Zhu et al., 2008). At the same time, a significant portion of the spray drifts to nontarget areas (Zhu et al., 2006b), which wastes pesticides, contaminates the environment, and exposes applicators, workers, and other people to pesticides, while increasing the costs of production. Many spray methods have been evaluated for improving application efficiency of pesticides in fruit farms and ornamental nurseries (Jeon and Zhu, 2012; Stover et al., 2003; Zhu et al., 2006a, 2006b, 2011b).
A laser-guided variable-rate intelligent sprayer was developed to increase the application efficiency of pesticides and foliar products in fruit farms and ornamental nurseries (Chen et al., 2012; Shen et al., 2017). The intelligent sprayer system uses a sensor to control pesticide application rate by adjusting the spray output of each nozzle based on the presence, structure, and foliage density of the crop, and the travel speed in real time. Chen et al. (2013a) reported that the intelligent spray system reduced spray volume from 47% to 73% at three different phenological stages of apple, compared with a conventional sprayer. Fessler et al. (2020) also reported that spray volume could be reduced between 59% and 83% after an air-assisted trailer sprayer was retrofitted with the laser-guided variable-rate control system in a commercial 8-year old Malus domestica ‘Golden Delicious’ apple orchard. No difference was found in spray coverage on sterling silver linden (Tilia tomentosa) and northern red oak (Quercus rubra) trees in ornamental nurseries between intelligent and conventional spray systems (Zhu et al., 2017), while the intelligent system reduced spray volume and drift to nontarget sites (Chen et al., 2013b).
Manandhar et al. (2020) reported that using an intelligent sprayer in Ohio apple orchards could reduce pesticide costs by 60% to 67%, with cost savings between $1420 and $1750 per ha. Within 1 to 4 years of using the intelligent sprayer in these apple orchards, the cost savings for a 4- to 20-ha apple orchard was estimated to equal the investment of the sprayer. However, to make the technology more versatile, its efficacy must be validated in complying with complex canopies of nursery and orchard crops under different environmental conditions, and it must be included in the integrated pest management (IPM) programs in the future.
The hypothesis of this research was that use of the laser-guided variable-rate intelligent sprayer under commercial fruit and ornamental nursery tree production conditions would significantly reduce pesticide volume needed to control insect pests and diseases. Thus, the objective was to evaluate efficacy of intelligent and conventional spray technologies for controlling insect and disease pests in a commercial fruit farm and two ornamental nurseries, while comparing pesticide use by the different spray technologies.
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