ABSTRACT

Plant disease diagnosis is a process that begins when a plant problem is first noticed at a field, garden, nursery, or greenhouse. A home gardener, farmer, or county agent observes the damaged plant(s) and the entire field and notes the obvious visible symptoms and signs. The distribution of the damage should be documented. Scattered or clumped distribution of the plant problem is often characteristic of a biotic disease whereas a row or obvious spray pattern is often indicative of pesticide injury or a cultural problem (Chapter 32). When entire fields or sections of fields are damaged with symptoms of uniform age, the problem is often due to an abiotic factor related to weather such as freeze, frost, or drought injury (Chapter 23). Information should be gathered on the history of the problem and site or planting area. All recent pesticide or fertilizer application dates and rates of application should be noted. Insect injury should be considered.