A few exceptions include Phytophthora root rot problems on noble fir in Christmas tree plantations or Port Orford cedar forest trees. Hill crests or steeply sloped areas are unlikely places to find Phytophthora diseases. Zoospores are attracted to the roots and begin the infection process.ĭiseased plants generally are in the lower areas of a field, where excess rain or irrigation water accumulates. During such events, this organism can produce swimming spores (zoospores). Excess water or poor drainage allows roots to become flooded for extended periods. Phytophthora diseases can be found on cranberries growing in low bogs near the coast or in the mountains on trees growing several thousand feet above sea level. Anywhere significant quantities of water collect, accumulate, or flow, Phytophthora spp. Flooded or saturated soils are not favorable to plant growth and can predispose plants to infection. They thrive, grow, reproduce, and infect plant roots in water, saturated soil, and along river banks and ponds. Phytophthora organisms are commonly referred to as water molds. These factors can be observed in flat open areas, undulating fields, sloped nursery container yards, or even in the greenhouse. The two main factors to look for when diagnosing Phytophthora-caused plant problems are the pattern of diseased plants and water drainage. 2, 3 Plant samples can also be taken to a laboratory for traditional or “high tech” tests to confirm the presence of this fungus-like organism. Knowing the biology of the Phytophthora organism and conditions that favor its development also helps the diagnosis. The evidence is in the field characteristics, field history, and symptoms of the affected plants. Time spent collecting all the information for an accurate diagnosis will aid management efforts in the long run.Ĭertain lines of evidence can quickly lead you toward (or away from) a Phytophthora disease diagnosis. 10 A wide variety of cultural and chemical controls can be implemented for Phytophthora problems. Although Phytophthora is a recognized disease problem in the Pacific Northwest, it has been misdiagnosed in the field half the time in Oregon. The first step in managing any of the several diseases caused by Phytophthora spp. Pscheidt, Extension Plant Pathology Specialist, OSU Aegerter, UC Cooperative Extension San Joaquin County (powdery mildew on field-grown tomatoes) Acknowledgement for Contributions to Diseases Stapleton, UC IPM and Kearney Agricultural Research and Extension Center, Parlierī.J. Miyao (emeritus), UC Cooperative Extension Yolo County Davis (emeritus), Plant Pathology, UC Davis UC IPM Pest Management Guidelines: Tomato In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action Group number for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number. Fungicides with a different group number are suitable to alternate in a resistance management program. Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. The longer of these two intervals is the minimum time that must elapse before harvest may take place. Preharvest interval (PHI) is the number of days from treatment until harvest can take place. Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. MODE OF ACTION GROUP NAME (NUMBER 1): Multi-site contact (M3) MODE OF ACTION GROUP NAME (NUMBER 1): Multi-site contact (M5) MODE OF ACTION GROUP NAME (NUMBER 1): Quinone outside inhibitor (11) + Dimethylation inhibitor (3) Do not alternate or tank mix with fungicides to which resistance has developed in the pathogen population. Make no more than 2 sequential applications before alternating with fungicides that have a different mode of action. MODE OF ACTION GROUP NAME (NUMBER 1): Quinone outside inhibitor (11)ĬOMMENTS: Apply at 5- to 7-day intervals. MODE OF ACTION GROUP NAME (NUMBER 1): Cinnamic acid (40) MODE OF ACTION GROUP NAME (NUMBER 1): Quinone outside inhibitor (11) + cyanoacetamide-oximes (27) Always read the label of the product being used. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. The following are ranked with the pesticides having the greatest IPM value listed first-the most effective and least likely to cause resistance are at the top of the table. Not all registered pesticides are listed. Pesticide precautions Protect water Calculate VOCs Protect bees
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