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Pythium species P. aphanidermatum P. irregulare P. mastophorum P. polymastum P. sulcatum P. ultimum P. uncinulatum P. violae Reported row crop hosts bean, beet, cabbage, carrot, cauliflower, cucumber, eggplant, lettuce, melon, onion, parsley, pea, pepper, potato, radish, spinach, sweet potato, tomato, watermelon asparagus, basil, bean, beet, Brussels sprouts, cabbage, carrot, cauliflower, celery, cilantro, cucumber, eggplant, endive, lettuce, melon, onion, parsley, pea, pepper, potato, radish, spinach, sweet potato, tomato, watermelon celery, parsley broccoli, cabbage, cauliflower carrot( infects other crops but causes few symptoms) bean, beet, Brussels sprouts, cabbage, carrot, cauliflower, celery, cilantro, cucumber, eggplant, endive, leek, lettuce, melon, onion, pea, pepper, potato, radish, spinach, sweet potato, tomato, watermelon lettuce carrot( infects other crops but causes few symptoms) Table 2. Examples of Pythium pathogens with broad vs. narrow host ranges "Fertigation delivers fertilizer to active roots. As long as irrigation is managed to deliver only needed water, fertigation can be a highly efficient method of fertilization." Continued from Page 15 Disease Development Development of Pythium diseases is straightforward. Initial inoculum is almost always linked with infested field soils and associated soil water. Pythium is a soilborne pathogen that resides in the soil primarily as dormant resting structures. Pythium inoculum is not seedborne or airborne. For Pythium to become active, grow, and produce those swimming zoospores, the soil must be wet for prolonged periods. Once susceptible seed, seedlings, and other plant parts are in close contact with Pythium inoculum, infection can take place and disease will be initiated. If wet soil conditions persist and temperatures are optimum for the pathogen, disease losses can be significant. Diagnostic Considerations Pythium is not the only soilborne pathogen that causes seedling damping-off and root rots of row crops. On spinach, damping-off and root rot can be caused by both Pythium and Fusarium; visually, one cannot distinguish between the symptoms caused by these two pathogens. Pythium and Phytophthora pathogens both cause dark, discolored roots of lettuce and cannot be differentiated in the field. Cauliflower transplants are susceptible to both Pythium and Rhizoctonia pathogens, both of which caused the roots to become Pythium plant pathogens can grow very rapidly. Pictured here are three-day-old cultures of Pythium, Phytophthora, Fusarium and Verticillium. The diameter of the petri dish is 85 mm. 16 Progressive Crop Consultant March / April 2021
NAVEL ORANGEWORM MANAGEMENT discolored. Precise and accurate diagnosis of Pythium diseases will therefore require lab-based tests and assays. Managing Pythium Controlling diseases caused by Pythium requires the implementation of IPM practices. Site selection: Choose to plant in fields that do not have a history of Pythium problems and have well-draining soils. Crop rotation: If Pythium is an issue, avoid planting the same susceptible crop in the infested field. Rotate to crops that are not known to be susceptible to the Pythium species present at that location. However, remember that some Pythium species have very broad host ranges (Table 2). Irrigation management: Because the Pythium pathogen is so strongly dependent on wet soil conditions, carefully schedule and limit irrigations to prevent overwatered, saturated soils. Time of planting: In some cases, moving the planting date to a different time of year may help reduce losses to Pythium. For example, depending on the Pythium species of concern, planting the crop in the warmer, drier summer may be preferred to seeding the crop in the cooler, wetter spring. Fungicides: Plant seed treated with a fungicide that is active against Pythium. Note that the fungicides used to control Rhizoctonia or Fusarium have no effect on Pythium. For some crops, applying fungicides to the emergent crop may provide additional protection. The repeated use of products having the same mode of action can result in Pythium isolates that are insensitive (=resistant) to those products; therefore, IPM strategies will require that thought be given to deploying different fungicides. Resistant or tolerant cultivars: Unfortunately, there do not appear to be any row crop cultivars that have genetic resistance to Pythium. Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com INCORPORAT ED INSECT PHEROMONE & KAIROMONE SYSTEMS Your Edge – And Ours – Is Knowledge. trece.com CIDETRAK ® NOW MESO • Turned on 24-7 • No maintenance/No second guessing • Full season results • More Pheromone distribution ® — Joe Coelho, Maricopa Orchards Joe’s IPM Program LEARN MORE © 2021, Trécé Inc., Adair, OK USA • TRECE, PHEROCON and CIDETRAK are registered trademarks of Trece, Inc., Adair, OK USA • TRE-1882, 1/21 March / April 2021 www.progressivecrop.com 17
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Page 32 and 33: Continued from Page 31 study (Figur
Page 34 and 35: Diamondback moth larva and adult (p
Page 36 and 37: Vegetable Growers Express Impressio
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Page 41 and 42: References Biofertilizers Market Si
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