Alex Stone, Oregon State University
This article is part of the Phil Foster Ranches Disease Management System Description
|Strategies and tools||Implementation details|
|I. System design|
|Landscape and field design||Farm has ranches at two locations with different temperature and moisture regimes (Santa Ana has insufficient water). Fields designed with aspect and airflow in mind. Rows oriented N-S whenever possible.|
|Resistant/resilient germplasm||Whenever possible, varieties selected for disease resistance.|
|Rotation||Crop rotation rules (Table 2).|
|Pathogen exclusion||Use of disease-free planting materials. Disease-destructive composting methods. Equipment sanitation.|
|II. Soil building for disease management|
|Soil quality (soil physical, chemical, and biological properties)||Organic amendments, cover cropping and reduced tillage improve soil physical properties (suppress soil moisture-related diseases) and soil biological properties (suppress damping-off).|
|Organic residue decomposition||Time, tillage, and irrigation speeds up crop residue decomposition before direct-seeded, susceptible crops such as onion, sweet corn, bean.|
|Nitrogen supply matched to crop need||Much crop N supplied by OM mineralization; relatively low quantities of supplemental fertilizer N applied as appropriate for each crop.|
|III. Cultural strategies|
|Drying of foliage and fruit||A. Drip irrigation: to avoid foliar and fruit wetting. B. Wide plant spacing: for crops such as lettuce and tomato to reduce humidity. Pruning in tomatoes. C. High tunnels to shed rain and prevent dew. D. Black plastic to prevent fruit/soil contact in peppers and cucumbers.|
|Overhead irrigation||On drip-irrigated peppers and carrots: eliminates the need for at least one sulfur spray targeted at powdery mildew.|
|Crop stress||Insect and weed pests controlled to minimize crop stress and wounding. Crops appropriately fertilized to avoid fertilization-induced diseases.|
|IV. Diagnosis, monitoring, recordkeeping, and decision-making|
|Disease diagnosis||No guessing: good samples are regularly provided to extension professionals for lab diagnosis.|
|Crops scouting||Scouting for disease occurs 2-3 times weekly. Rapid response to first symptoms (eg. downy mildew in onions, Septoria in celery).|
|Recordkeeping||Scouting records include disease onset, incidence and severity.|
|Data-based management decisions||Location of soilborne diseases used for rotation planning. Thresholds for disease management materials are developed from monitoring records. Records of timing of disease initiation used to time preventive applications.|
|V. Supplemental inputs|
|Inputs||Pesticides are appplied to very few crops (examples: sulfur for powdery mildews, Regalia for downy mildew of cucumber). Goal is to learn when and why diseases start so materials can be applied preventively.|
|Temporal Rotation: Soilborne Disease Management|
|Alliums: 5 years out||Always||Control of Fusarium basal rot and pink root of onions||Effective for pink root but only somewhat effective for Fusarium basal rot. Corn is alternate host for pink root.|
|Lettuce: 2-4 years out||Always||Controls Sclerotinia lettuce drop (2 yrs), and Anthracnose of lettuce (4 yrs)||Prickly lettuce is alternative host for Anthracnose, so this rotation is not 100% effective.|
|Solanaceae: 3-4 years out||Always||Helps manage Phytophthora root rot of pepper||Not effective for Verticillium wilt of potato|
|Cucurbitaceae: 3 years out||Always||Controls diseases such as angular leaf spot||Not effective for Verticillium wilt of melon and watermelon|
|Brassicaceae: 2 years out||Always||Controls clubroot||Effective in combination with soil pH>7.2|
|No successive planting of the same crop family||Almost always||(a) Beet cyst nematode vs. brassicas and the chard family. We try to keep these plant families out of the SJ block that has cyst nematode; (b) Fusarium root rots|
|No successive planting of the same crop||Always||Controls Septoria of celery||Effective for Septoria|
|No successive planting of monocots||Always||Reduces risk of diseases that affect grasses/cereals and alliums (e.g. Phoma terrestris, pink root of onion http://ipm.ucanr.edu/PMG/r584100711.html)||Likely helpful|
|Specific Disease-Suppressive Pre-Crop Rotation: Soilborne Disease Management|
|Broccoli crop before crops susceptible to Verticillium||Tried and abandoned||Broccoli pre-crops have been shown to suppress Verticillium wilt in subsequent crops||Seems ineffective against Verticillium wilt of watermelon. Multiple crops of broccoli before watermelon has been recommended but neither tried nor practical
|Oat or sudangrass crop before crops susceptible to Verticillium||Tried and abandoned||Oats and Sudan are non-hosts of Verticillium: avoids further inoculum increase||Ineffective against Verticillium wilt on all susceptible crops|
|Spatial Rotation: Airborne Disease Management|
|Widely separate successive crop blocks from each other (spatial rotation)||Almost always: for specific crops and time periods||Wind-spread disease propagules contact close targets more often than targets further away||Seems to be helpful for crops with a significant susceptibility to an endemic wind-spread disease: garlic rust, downy mildew of cucumber|
|Plant crops on different ranches (different climates), seasonally||Always, for specific crops||Weather-susceptible diseases may be reduced or encouraged by temperature, humidity and rainfall||Seems to be helpful for crops with a known susceptibility to an endemic wind-spread disease: powdery mildew of carrot and fennel, garlic rust, downy mildew of lettuce and onion|
|Plant successive blocks of the same crop upwind||Always, for specific crops||Wind and rain-spread disease propagules may be blown away from younger blocks||Seems to be helpful for crops with a known susceptibility to an endemic wind-spread disease: powdery mildew of carrot and fennel, downy mildew of lettuce and onion|
|Environment-based Rotation: Soilborne Disease Management|
|Avoid high-risk disease environments||Always, for specific crops and diseases||Avoid planting potatoes and red onion into warm soils to minimize Verticillium wilt and Fusarium basal rot, respectively; avoid planting beets into cool soils to avoid damping off||Somewhat effective|
Figure. 1. Highest disease severity score observed each year for Phytophthora root rot of pepper. From scouting records, Phil Foster Ranches, 1990’s-2014. Scoring scale ranged from 1 (very light damage, very few plants) to 5 (heavy damage, many plants).
Figure 2: Highest disease severity score recorded each year for anthracnose of lettuce. From scouting records, Phil Foster Ranches, 1998-2014. Scoring scale ranged from 1 (very light damage, very few plants) to 5 (heavy damage, many plants). Anthracnose occurs only in Santa Ana and only in the earliest lettuce plantings (plantings 1-3).
Figure 3: Spinach yield at Phil Foster Ranches, 1994-2014. PFR adopted new downy mildew resistant varieties as they became available. Resistant varieties increased yields for one to several years, after which the pathogen overcame the resistance and yields declined. PFR ceased growing spinach in 2012.
Figure 4: Severity of Verticillium wilt at Phil Foster Ranches 1997-2014.
Figure 5: Watermelon yield at Phil Foster Ranches, 1997-2014.
Figure 6: Cantaloupe yield at Phil Foster Ranches, 1997-2014.
Figure 7: Highest disease severity score recorded each year for Fusarium basal rot of onion. From scouting records, Phil Foster Ranches, 1997-2014. Scoring scale ranged from 1 (very light damage, very few plants) to 5 (heavy damage, many plants).
Figure 8: Red onion yield at Phil Foster Ranches, 1997-2014.
Figure 9: Cucumber yield at Phil Foster Ranches, 1994-2014.
Figure 10: Pepper Yield at Phil Foster Ranches, 1994-2014.
Figure 11a: The highest number of sulfur applications to a pepper planting (for powdery mildew; later plantings typically receive more applications than earlier plantings) per year at Phil Foster Ranches, 2002-2015. Pepper powdery mildew is controlled by sulfur applications initiated before pathogen infection (see 11b).
Figure 11b: Date of the first sulfur spray each year for control of powdery mildew of pepper at Phil Foster Ranches, 1995-2013.
Figure 12: Lettuce yield at Phil Foster Ranches, 1994-2014.
Figure 13: Celery yield at Phil Foster Ranches, 1994-2014.
Figure 14: Garlic yield at Phil Foster Ranches, 1994-2014. The yield target of 400 boxes per acre is rarely achieved as rust suppresses yield.
Figure 15: Average number of annual sulfur applications to a garlic planting for the control of garlic rust. Despite these applications, rust continues to suppress garlic yields.
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