Updated August, 2020.
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 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. CRAIG ADD TABLE HERE
| 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 | |
| Muskmelon=cantaloupe &Watermelon |
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 |
| 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 | |
| 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 |
More information/prepared by:
Alan A. MacNab1and Thomas. A. Zitter2
1Penn State University, University Park, PA; 2Cornell University, Ithaca, NY
Margaret Tuttle McGrath
Associate Professor
Long Island Horticultural Research and Extension Center (LIHREC)
Plant Pathology and Plant-Microbe Biology Section
School of Integrative Plant Science
College of Agriculture and Life Sciences
Cornell University
mtm3@cornell.edu