 |
| MINIMIZING
VEGETABLE DISEASE |
|
 |
|
To grow a healthy vegetable garden, one with few or no diseases,
some general practices should be used. The following ten
steps will maintain healthy plants and reduce the need for fungicides.
You may be able to devise others which are especially suitable to
your garden.
1. CHOOSE RESISTANT OR TOLERANT VARIETIES:
The easiest and most important way to manage plant diseases is to
choose resistant or tolerant varieties. The letter abbreviations used
to describe the resistance of a variety (for example, VF = Verticillium
and Fusarium wilt resistant, PM = powdery mildew resistant or tolerant)
are listed in seed catalogs or can be explained by your County Cooperative
Extension Agent. Resistant varieties resist infection by a particular
disease agent and show little or no disease. Tolerant varieties may
show symptoms but still yield the same as resistant varieties or susceptible
ones protected with pesticides. When available, choose varieties that
are resistant or tolerant to a disease that previously has been a
problem.
2. PURCHASE SEED TREATED WITH FUNGICIDES AND INSECTICIDES:
Seed may come pre-treated with a dusting of a fungicide and an insecticide,
or you may dust the seed with a fungicide such as captan or thiram
according to the directions on the LABEL. This coating will help prevent
the seed from rotting in the soil prior to germination and can also
help protect the newly emerging seedling from "damping off".
If seed rot or damping off have been problems in your garden, then
treating the seed with a fungicide may be helpful.
3. PURCHASE DISEASE-FREE SEED, TRANSPLANTS,
PROPAGATING MATERIAL:
Begin with healthy plant material to help plants become quickly established
in the garden. Plant materials that are unhealthy at the start never
yield as much as healthy ones or may die while still young. Reputable
seed companies sell only disease-free plant materials. Some seeds
are hot water treated to remove infectious agents. Some are tested
to reduce the risk of seed-borne viruses. When shopping for transplants
or other propagating material, take time to thoroughly examine the
plant stock to make sure it is healthy and vigorous. If you save your
own seed, harvest it from healthy plants and dry it thoroughly. Store
such seed in properly labeled airtight containers in a cool, dry place.
4. SELECT A SUNNY, WELL-DRAINED LOCATION:
A sunny area with well-drained soil is an ideal site for vigorous
growth of garden plants. Shaded, poorly drained areas support weak
and spindly plants that are easy targets for disease organisms. Even
if such plants remain alive and free of infectious disease, they will
not yield as much as strong and burly plants.
5. IMPROVE THE SOIL ENVIRONMENT:
When there is no other choice for a garden site but a heavy, wet soil,
plant in raised beds or ridged rows so the soil around the plants'
roots will be drier. Heavy wet soils discourage healthy root growth
and encourage roots. When a garden is established on sloped terrain,
plant in terraced beds to reduce soil erosion over delicate, young
plants and newly sown seed. Soils that are dry and sandy may be mulched
with a variety of materials (straw, grass clippings, black plastic,
etc.) to help retain moisture. A soil environment that is favorable
to healthy root development will support the growth of healthy plants.
6. WATER AND FEED PLANTS:
Plants require one inch of rainfall per week for best growth. If rainfall
is inadequate, water the garden. Water plants in the morning so they
will dry off quickly above ground, reducing the chances of disease
spread. Also avoid using overhead, sprinkler irrigation because it
can promote the development and spread of leaf, flower , and fruit
infections. Trickle irrigation is best because it puts water directly
in the root zone, does not wet the plants above ground, nor encourage
soil splashing. Plants that are fertilized properly at planting time
and as a sidedress will grow better and healthier. Always use a complete
fertilizer or incorporate a well-rotted manure or rich compost into
the soil. Avoid over-fertilization because this will injure plant
roots directly.
7. SPACE PLANTS TO ALLOW AIR CIRCULATION:
High humidity and moisture favor the development of diseases on the
tops of plants. Allowing enough room for plants to grow and space
for air to circulate around mature plants reduces the humidity and
promotes rapid drying of plant surfaces. This in turn helps reduce
disease incidence.
8. PRACTICE CLEANLINESS IN THE GARDEN:
Always remove from the garden area plant materials that show signs
of a disease and destroy them in the trash. Work in the garden when
plants are dry because moisture on plants aids the spread of infectious
diseases. Composting, unless the pile becomes very hot, does not effectively
eliminate diseases from plant refuse under New York climate conditions.
for this reason it is unwise to compost any diseased plant material.
At the end of the growing season clean up all crop debris because
disease agents will overwinter in this plant material and infect new
plants the following season.
9. PLANT A FALL COVER CROP AND PLOW IT IN THE FOLLOWING
SPRING:
After cleaning up the garden, sow a grass, like perennial rye, which
will begin to grow that fall. This cover crop will protect the top
soil from erosion during the winter months. The following spring plow
in the rye grass to enrich the soil with fresh organic matter or "green
manure". This practice also helps reduce the populations of certain
soil-borne disease agents. Other, non-infectious, agents flourish
on the green manure in the soil and tend to inhibit the infectious
ones.
10. ROTATE CROPS:
Successive planting of one crop family in the same area over many
seasons promotes the buildup of disease agents in the soil. Thus,
disease becomes more severe over time. Rotate plants to different
areas of the garden to help reduce the losses due to soil-borne disease
agents. Avoid successive planting within crop families or crop types
such as crucifers (cabbage, broccoli, turnip, radish, etc.), cucurbits
(melon, cucumber, squash, etc.), solanaceous (tomato, eggplant, potato,
pepper), grasses (sweet corn, cover crops such as rye), legumes (bean,
pea), and root crops (carrot, beet, onion).
Last updated, KLS, 10/99
__________________________________________________________________________________
The Plant Disease Diagnostic Clinic
at Cornell University is located at 334 Plant Science Building,
Ithaca, NY, 14853. Phone: 607-255-7850, Fax: 607-255-4471,
Email: kls13@cornell.edu
or slj2@cornell.edu
|