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Dharmalingam S. Pitchay, John Gray, Jonathan M. Frantz, Leona Horst and Charles Krause

Geranium (Pelargonium ×hortorum) typically follows the C3 metabolic pathway. However, it switches to CAM metabolism under certain abiotic stress environments. This switch may affect the nutritional requirement and appearance of visible deficiency symptoms of these plants. Because potassium (K) plays a key role in stomatal function, K-deficiency was studied in geranium. Plants were grown hydroponically in a glass greenhouse. The treatments consisted of a complete, modified Hoagland's solution with millimolar concentrations of macronutrients, 15 NO3-N, 1.0 PO4-P, 6.0 K, 5.0 Ca, 2.0 Mg, and 2.0 SO4-S and micromolar concentrations of micronutrients, 72 Fe, 9.0 Mn, 1.5 Cu, 1.5 Zn, 45.0 B, and 0.1 Mo, and an additional solution devoid of K. It took longer to develop the classic K deficiency symptoms than other bedding plant species commonly require. The K-stress plants' dry weight was 10% and 37% of control at incipient and advanced stage, respectively. When portions of geranium leaves were covered, symptomology on leaves with K stress developed rapidly (within 2 days) compared to the uncovered portion of the leaf blade. Control plants contained an abundance of marble-shaped K crystals in the adaxial surface of leaf mesophyll, but were lacking in the K-deficient plants. Geranium is more prone to K stress during short days than long days and an additional supply of K would be needed for normal growth in short days.

Open access

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.