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Do Rotations Matter within Disease Management Programs?

Alan A. MacNab1and Thomas. A. Zitter2

1Penn State University, University Park, PA; 2Cornell University, Ithaca, NY


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This page has been updated and moved to: https://www.vegetables.cornell.edu/pest-management/disease-factsheets/do-rotations-matter-within-disease-management-programs/ As agricultural land becomes more scarce, existing farms become more specialized, and land closest to roadside markets increases in value, in part due to the advertisement-value of growing some crops where they can be seen and/or harvested by customers, an increasing number of farmers are considering shorter rotations for some of their plantings. Indeed, it can be very tempting to shorten rotations.

What would happen if one were to ignore rotations, that is, if one were to plant the same crop in the same field year after year? This was done in Penn State research fields for both tomatoes and for muskmelons. The results are summarized below in Table 1 (tomato early blight) and Table 2 (muskmelon/cantaloupe Alternaria blight).

Table 1. Defoliation associated with Alternaria early blight on tomatoes after growing tomatoes in the same field for 1, 2, 3, and 4 successive years).

Successive Years % Defoliation when
5% Fruit were Ripe
Year 1 3
Year 2 30
Year 3 74
Year 4 70


Table 2. Date when Alternaria blight first appeared on muskmelons (cantaloupes) for successive years after muskmelons were grown repeatedly in the same field (from 1977 through 1981).

Successive Years Years Grown First Date when Alternaria
Blight was first observed
# Days before
August 8
# Days after
June 1
Year 1 0 August 8 0 69
Year 2 1 August 3 5 64
Year 3 2 July 29 10 59
Year 4 3 July 25 14 55
Year 5 4 July 18 21 48

The results provide a clear indication of the value of rotations relative to diseases caused by pathogens that can survive either in soil or in association with refuse from diseased plants. Many vegetable diseases are in this category.

Traditional wisdom and common-sense, combined with results such as those presented in tables above, tell us that rotations are important. Interpretation of results from various field, greenhouse and lab studies, and observations by many plant pathologists, suggest a minimum number of years that a grower should avoid growing crops affected by specific diseases (See Table 3). All vegetable growers should consider this information seriously as they plan crop rotations within their disease management programs.

Table 3. Minimum years to avoid crops susceptible to specific diseases.

Vegetable Disease Period without a susceptible crop
Asparagus Fusarium wilt & root rot Indefinite; do not plant without fumigation
Beans Root rots 3 years; use grain crops, including sweet corn in rotation
  White mold, Sclerotinia 3 years; avoid tomato, potato, lettuce,cabbage, celery, carrot
  Anthracnose 2 years
  Bacterial blight 2 years
Beets Cercospora leaf spot 3 years
  Root rots 3 years; use grain crops, including sweet corn in rotation
Cabbage-related plants Clubroot 7 years; avoid turnip, radish; adjust pH to 6.8 or above
  Fusarium yellows Many years
  Blackleg 3-4 years; avoid turnip
  Black rot 2-3 years; avoid turnip
  White mold 3 years; use grains crops, including sweet corn in rotation
Carrots Leaf blights (fungal & bacterial) 2-3 years
Celery Leaf blights 2 years
Corn, sweet Smut 2-3 years
  Yellow leaf blight 3 years
  Northern leaf blight 2 years
Cucumber Scab, GSB, & leaf spots 2 years
Eggplant Verticillium wilt

4-5 years; avoid tomato, potato, pepper, strawberry, brambles

  Fruit rots 3 years
Lettuce Bottom rot (Rhizoctonia) 3 years
  Drop, Sclerotinia

3 years; avoid tomato, potato, beans, cabbage, celery, carrot

Leaf spots, GSB, & scab 2+ years; avoid other cucurbits
  Fusarium wilt 4+ years; watermelon Fus. wilt is different
  Gummy stem blight (GSB) 2 years; avoid muskmelon, pumpkin, squash
  Fusarium wilt 4+ years; muskmelon Fus. wilt is different
Onion Leaf blights 1-2 years
Parsley Damping-off 3 years
Parsnip Leaf spot & root canker 1 to 2 years
Peas Root rots 3 to 4 years
  Fusarium wilt 4 to 5 years
Peppers Bacterial spot 2 years
  Phytophthora blight 3 years; avoid tomato, eggplant, cucurbits
Potato Verticillium wilt 3-4 years without tomato, eggplant, pepper
  Sclerotinia stalk rot

4 years; avoid tomato, lettuce, beans, cabbage, celery, carrot

  Rhizoctonia canker 2-3 years; best with 2 yr. grass or 1 yr cereal
  Silver Scurf 2 years; primarily from seed tubers
  Early blight 2 years; avoid tomato
  Pythium leak; pink rot 4 years
  Common scab 2-3 years; no root crops; adjust pH to 5.2 or below
Pumpkin, & Winter squash Angular leaf spot 1-2 years
  Black rot (GSB) 2+ years; avoid muskmelon, watermelon, and other cucurbits
  Fusarium crown and fruit rot 3 years; avoid other cucurbits
  Phytophthora blight 3 years; avoid tomato, pepper, eggplant, and other cucurbits
  Scab 2 years
Radish Clubroot 7 years; avoid turnip, cabbage-related plants; adjust pH to 6.8
Turnip Clubroot 7 years; avoid radish, cabbage-related plants; adjust pH to 6.8
Spinach Downy mildew & white rust 2 years
Sweet potato Black rot & scurf 3 years
  Pox (soil rot) Few years; reduce soil pH below 5.2
Tomato Bacterial canker 3+ years
  Bacterial spot 2 years; avoid pepper
  Bacterial speck 1 year
  Early blight 2 years; avoid potato
  Anthracnose 2-3 years; avoid potato
  Septoria leaf spot 1-2 years
  Fusarium wilt 3 years
  Verticillium wilt Several years; longest possible; avoid potato and eggplant