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Heping Zhu, James Altland, Richard C. Derksen and Charles R. Krause

Spray deposition and coverage at different application rates for nursery liners of different sizes were investigated to determine the optimal spray application rates. Experiments were conducted on 2- and 3-year-old ‘Autumn Spire’ red maple (Acer rubrum) liners. A traditional hydraulic sprayer with vertical booms between tree rows was used to apply the spray applications. Application rates were 10, 20, 30, and 40 gal/acre for the 2-year-old liners and were 20, 40, 60, and 80 gal/acre for the 3-year-old liners. Nylon screens were used to collect spray deposition of a fluorescent tracer dissolved in water, and water-sensitive papers were used to quantify spray coverage inside canopies. Spray deposition, coverage, and droplet density inside both 2- and 3-year-old liner canopies increased as the application rate increased. The minimum rates to spray 6.6-ft-tall, 2-year-old ‘Autumn Spire’ red maple liners and 8.7-ft-tall, 3-year-old liners were 20 and 40 gal/acre, respectively. An exponential equation was derived from these results to estimate the spray application rate required for different tree liner heights and to minimize excessive chemical use in rapidly growing tree liners.

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Jonathan M. Frantz, Dharmalingam S. Pitchay, Glen Ritchie and Heping Zhu

Nitrogen (N) is often supplied to plants in excess to minimize the possibility of encountering N deficiency that would reduce the plant quality due to leaf chlorosis and necrosis. This is not only costly, but it can reduce the quality of plants, predispose the plants to biotic stress such as Botrytisgray mold, and extend the production cycle. Several tools can be used to identify N deficiency in plants, and most are based on chlorophyll reflectance or transmittance. While sensitive when plants are experiencing N deficiency, spectral signals can saturate in an ample N supply and make it difficult to discern sufficient and supra-optimal N nondestructively. Three diverse ornamental species (begonia, Begoniacea×tuberhybrida; butterflybush, Buddlejadavidii; and geranium, Pelargonium×hortorum) were grown with a broad range of N supplied (1.8 to 58 mm) in three separate studies that resulted in a range of 1.8% to 6% tissue N concentration. Using a spectroradiometer, we measured reflectance from the whole plants twice over a period of 3 weeks. A first-derivative analysis of the data identified six wavebands that were strongly correlated to both begonia and butterflybush tissue N concentration (r 2 ∼ 0.9), and two of these also correlated well to geranium N concentration. These wavebands did not correlate to chlorophyll peak absorbance, but rather blue, green, red, and far-red “edges” of known plant pigments. These wavebands hold promise for use as a nondestructive indicator of N status over a much broader range of tissue N concentration than current sensors can reliably predict.

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Liming Chen, Matthew Wallhead, Michael Reding, Leona Horst and Heping Zhu

Laser-guided variable-rate intelligent spray technology is designed to significantly reduce pesticide use with a positive impact on the environment. However, there have been no reports on applying this technology to commercial fruit farms. Comparative experiments of intelligent variable-rate and conventional constant-rate spray applications for pesticide use and pest control were conducted at a fruit farm in Ohio during two consecutive growing seasons. Apple (Malus pumila), peach (Prunus persica), blueberry (Vaccinium section Cyanococcus), and black raspberry (Rubus occidentalis) were used for the tests. Pest severity of codling moth (Cydia pomonella), oriental fruit moth (Grapholitha molesta), scab (Venturia inaequalis), and powdery mildew (Podosphaera leucotricha) in apple; oriental fruit moth, brown rot (Monilinia fructicola), and powdery mildew (Podosphaera pannosa) in peach; spotted wing drosophila (Drosophila suzukii), mummy berry (Monilinia vaccinii-corymbosi), and phomopsis (Phomopsis vaccinii) in blueberry; and anthracnose (Elsinoe veneta) in black raspberry were assessed. There was equal severity of pests between intelligent and conventional spray applications, whereas the intelligent spray reduced pesticide use by 58.7%, 30.6%, 47.9%, and 52.5% on average for apple, peach, blueberry, and black raspberry, respectively. These results illustrate that intelligent spray technology is more environmentally friendly than conventional standard spray technology and equally or more effective for control of insect and disease pests in fruit production.