This is not only the season for growing annuals in South Florida it is also the season for growing vegetables. You don’t need a lot of land to grow a few vegetable plants and enjoy some fresh produce from your own produce patch. Unfortunately, many gardeners lose their plants because of insects and diseases.
Disease causing organisms such as fungi, bacteria, viruses and nematodes are too small to see with the naked eye making diagnosis before damage unlikely. Following are some tips for symptoms and poor horticultural practices to watch out for.
Fungi can cause stunting, spots, blights, galls or rots on all plant parts. The time between entry of the fungus and appearance of symptoms can be anywhere from three days to two weeks depending on the disease and plant involved. Temperature and moisture are two factors which can influence disease development.
Bacteria can cause many of the same symptoms as fungi including stunting, leaf spots, wilts, fruit rots or galls. Bacteria live and thrive in seeds, transplants, soil and weeds. They can be spread by irrigation and wind driven rains. Bacteria enter plants through natural openings or insect wounds. Incubation periods are three days to a week.
Viruses will cause leaf mosaics or mottling, fruit mosaics, leaf distortions and stunting. Problems caused by viruses look similar to those caused by herbicides and nutritional deficiencies. They can be spread on seed, especially beans and peas. Aphids can also spread many viruses throughout a garden. Gardens next to a weedy field are more likely to have aphid-transmitted viruses. Incubation periods are from a few days to a few weeks.
Nematodes are round, worm-shaped animals which live in the soil. There are hundreds of different kinds living in the Florida soils, some which are beneficial. Those which feed on plants can severely reduce the health, vigor, productivity and value of vegetables. Stunting, wilting and slow growth are symptoms of a nematode infected plant.
Finally, there are problems caused by horticultural problems like nutritional deficiencies or herbicide damage. Blossom end rot of tomatoes and peppers is caused by a calcium deficiency. This deficiency can be caused by soil moisture fluctuations from wet to dry during the growth period. Herbicides used on lawns can drift into the garden causing plant deformation. Chemical burns from insecticides, fungicides and excessive fertilization are possible. You should always use the correct amounts of these chemicals to prevent problems.
The best control of plant diseases and nematodes is prevention. How you prepare your garden before planting is very important.
1. Site selection: A sunny location helps with plant growth and reducing disease development.
2. Drainage: Excess soil moisture encourages growth of soil fungi and nematode caused root rots. Too much moisture can deplete oxygen slowing root development and exposing roots to infection by soil fungi.
3. Soil tillage: Undecomposed plant debris or green plant matter can be a source of fungi, bacteria, viruses and nematodes. Do your tilling early to allow for the breakdown of any green matter.
4. Disease free seeds: Purchase disease-free seed to avoid many fungal, bacterial and viral diseases which can be transmitted by seed.
5. Fungicide seed treatment: Seed treated with a fungicide can reduce seed rot and pre-emergent seedling decay caused by fungi. Bulk vegetable seed sold at garden shops is often treated with a fungicide. Seed sold in small packets may not be treated. If seeds appear to be coated with brightly colored dye that is a sign that the seeds have been treated. For unprotected seed you can purchase a seed treatment and do it yourself.
6. Healthy transplants: Transplants you purchase should be healthy and vigorous. If roots have galls or symptoms of disease don’t buy them. For best results grow your own transplants.
7. Soil treatment: Treatment of the soil before planting is the best method for controlling nematodes and soil borne disease. Soil fumigants will effectively control nematodes, soil borne diseases and many weeds. Caution should be used as fumigants can damage neighboring plants and grasses. This treatment should be completed at least two weeks before planting. Another method of treatment is soil solarization. While successful in some cases it does not penetrate the soil to the depth of fumigants. Soil solarization involves covering the area with clear plastic and keeping the soil moist, but not wet, for a period of four to six weeks. This should be done during the hottest months of summer, July and August. Advanced planning is needed for either treatment method.
8. Crop rotation: Alternating the crops planted on a given site within the garden or changing the garden site every year reduces disease problems.
9. Raised beds and mulches: Raised beds help minimize moisture damage caused by too much rain or irrigation. Mulches help keep the soil from drying out and also prevents vegetables from direct contact with the soil which could cause rot.
10. Spacing: Crowding plants allows moisture to remain on plants longer due to shading and reduced air movement causing disease problems.
After planting chores are just as important for a healthy crop of vegetables.
1. Observation: Try to check your garden daily. Many diseases start as a few spots or on one plant. If you remove the diseased leaves or plants when first noticed you will prevent an epidemic in the garden.
2. Spraying: Foliar fungicides will control rusts, mildew, fruit rot and leaf spots. Fungicides are preventative not curative so you need to apply before you have a problem.
3. Staking and mulching: Both will reduce direct contact of the vegetables with the soil.
4. Remove old flower petals: Wet rot usually begins on spent petals progressing into the fruit where it causes rot. This is a big problem with squash.
5. Insect control: Insects cause wounds allowing fungi and bacteria to enter and grow in the plant. This can cause diseases like root and stem rots or soft rots of fruit and stems. Insects can also transmit viruses.
6. Good horticultural practices: Keep your garden well watered but not wet. Never allow the plants to dry and wilt. This will cause stress making them more susceptible to problems. Fertilize when planting and to keep the plants healthy and vigorously growing.
And keep the garden as weed and insect free as possible.
Vegetables you can plant now include, but are not limited to, beets, broccoli, cabbage, carrots, cauliflower, celery, lettuce, mustard, onions, peas, radish, spinach, squash, strawberries, turnips and tomatoes. Take proper care of your vegetable garden and you will be sharing the bounty with friends, neighbors and those less fortunate.
Eileen Ward and her husband Peter have owned and operated Greensward of Marco, Inc., a lawn maintenance and landscaping company, since 1981.