This publication is a joint effort of the seven disciplines that comprise the Georgia Vegetable Team. It is comprised of 14 topics on tomato, including history of tomato production, cultural practices, pest management, harvesting, handling and marketing. This publication provides information that will assist producers in improving the profitability of tomato production, whether they are new or experienced producers.
Tomatoes are an important crop for Georgia growers; however, successful tomato production is not easily achieved. Tomato production requires highly intensive management, production and marketing skills, and a significant investment. Per acre cost of production is high, and yields can be severely limited by pest problems or environment. Tomato production is complex. Expertise in the areas of cultural practices, soils and fertility management, pest control, harvesting, post-harvest handling, marketing, and farm record keeping is crucial to profitable production.
In writing this publication, the authors have strived to provide a thorough overview of all aspects of tomato production. However, chemical pest control recommendations are not included, as these change from year to year. For up-to-date chemical recommendations, see the current Georgia Pest Management Handbook.
William Terry Kelley and George Boyhan, Extension Horticulturists
The tomato (Lycopersicon esculentum Mill.) is the most widely grown vegetable in the United States. Almost everyone who has a garden has at least one tomato plant. They can even be produced in window box gardens or in single pots. Commercially, it is of equally great importance. From processing to fresh market, and from beefsteak to grape tomatoes, the variety and usefulness of the fruit is virtually boundless.
Tomatoes are members of the Solanaceae family, which includes peppers, eggplant, Irish potatoes and tobacco. The tomato originated in the area extending from Ecuador to Chile in the western coastal plain of South America. The tomato was first domesticated in Mexico where a variety of sizes and colors were selected. The fruit was introduced to Europe in the mid-1500s. The first ones introduced there were probably yellow since they were given the name pomodoro in Italy, which means “golden apple.” Later the names poma armoris and pomme d’amour were used in Italy and France. These names are both translated as “love apple.”
Tomatoes are members of the nightshade family and, because of this, were considered for many years to be poisonous. Indeed, many crops in this family contain highly toxic alkaloids. Tomatine occurs in toxic quantities in the tomato foliage but is converted enzymatically to a non-toxic form in the fruit. Because of these beliefs, the crop was not used for food until the 18 th century in England and France. Tomatoes were introduced to the United States in 1710, but only became popular as a food item later in that century. Even as late as 1900, many people held the belief that tomatoes were unsafe to eat.
Use of the crop has expanded rapidly over the past 100 years. Today more than 400,000 acres of tomatoes are produced in the United States. The yearly production exceeds 14 million tons (12.7 million metric tons), of which more than 12 million tons are processed into various products such as soup, catsup, sauce, salsa and prepared foods. Another 1.8 million tons are produced for the fresh market. Global production exceeds 70 million metric tons. Tomatoes are the leading processing vegetable crop in the United States.
California is the leading producer of processing tomatoes in the United States. Indiana, Michigan and Ohio are other major producers. California and Florida are the leading fresh market tomato producers in the United States. Ohio, Tennessee, Virginia and Georgia produce significant amounts of fresh market tomatoes as well.
Tomatoes have significant nutritional value. In recent years, they have become known as an important source of lycopene, which is a powerful antioxidant that acts as an anticarcinogen. They also provide vitamins and minerals. One medium ripe tomato (~145 grams) can provide up to 40 percent of the Recommended Daily Allowance of Vitamin C and 20 percent of Vitamin A. They also contribute B vitamins, potassium, iron and calcium to the diet.
There are two types of tomatoes commonly grown. Most commercial varieties are determinate. These “bushy” types have a defined period of flowering and fruit development. Most heirloom garden varieties and greenhouse tomatoes are indeterminate, which means they produce flowers and fruit throughout the life of the plant.
Tomato is considered a tender warm season crop but is actually a perennial plant, although it is cultivated as an annual. It is sensitive to frost and will not grow perpetually outdoors in most parts of the country. Most cultivated tomatoes require around 75 days from transplanting to first harvest and can be harvested for several weeks before production declines. Ideal temperatures for tomato growth are 70-85 degrees F during the day and 65-70 degrees F at night. Significantly higher or lower temperatures can have negative effects on fruit set and quality. The tomato is a self-pollinating plant and, outdoors, can be effectively pollinated by wind currents.
W. Terry Kelley and George Boyhan, Extension Horticulturists
Tomatoes can be produced on a variety of soil types. They grow optimally in deep, medium textured sandy loam or loamy, fertile, well-drained soils. Avoid sites that tend to stay wet. Also, rotate away from fields that have had solanaceous crops within the past 3-4 years. Select sites that have good air movement (to reduce disease) and that are free from problem weeds.
In field production, plants depend on the soil for physical support and anchorage, nutrients and water. The degree to which the soil adequately provides these three factors depends upon topography, soil type, soil structure and soil management.
For tomato production, proper tillage is crucial for adequate soil management and optimal yields. Land preparation should involve enough tillage operations to make the soil suitable for seedling or transplant establishment and to provide the best soil structure for root growth and development.
The extent to which the root systems of tomato plants develop is influenced by the soil profile. Root growth will be restricted if there is a hard pan, compacted layer or heavy clay zone. Tomatoes are considered to be deep rooted and, under favorable conditions, some roots will grow to a depth of as much as 10 feet. The majority of roots, however, will be in the upper 12 to 24 inches of soil. Since root development is severely limited by compacted soil, proper land preparation should eliminate or significantly reduce soil compaction and hard pans.
Tillage systems using the moldboard (“bottom” or “turning”) plow prepare the greatest soil volume conducive to vigorous root growth. This allows the development of more extensive root systems, which can more efficiently access nutrients and water in the soil. Discing after moldboard plowing tends to re-compact the soil and should be avoided.
Compaction pans are present in many soils. They are formed principally by machinery and are normally located at or just below plow depths. Although compaction pans may be only a few inches thick, their inhibitory effects on root growth can significantly reduce tomato yields.
If a compaction pan exists just below or near moldboard plow depth, this hard pan can be disrupted by subsoiling to a depth of 16 to 18 inches to allow the development of a more extensive root system. Subsoiling also helps increase water infiltration.
If there is an abundance of plants or plant residues on the soil surface, discing or mowing followed by discing is usually advised prior to moldboard plowing. This should be done 6 to 8 weeks ahead of planting to bury residue and allow it to decay. Immediately prior to plastic mulch installation or transplanting, perform final soil preparation and/or bedding with a rotary tiller, bedding disc or a double disc hiller in combination with a bedding press or leveling board. This provides a crustless, weed-free soil for the installation of plastic mulch or the establishment of transplants.
Tomatoes are usually transplanted into plastic mulch on raised beds. A raised bed will warm up more quickly in the spring and therefore will enhance earlier growth. Since tomatoes do poorly in excessively wet soils, a raised bed facilitates drainage and helps prevent waterlogging in low areas or in poorly drained soils. Raised beds are generally 3 to 8 inches high. Keep in mind, however, that tomatoes planted on raised beds may also require more irrigation during drought conditions.
Winter cover crops help protect the soil from water and wind erosion. When incorporated into the soil as “green manure,” cover crops contribute organic matter to the soil.
Soil organic matter consists of plant and animal residues in various stages of decay. Organic matter improves soil structure (helps to reduce compaction and crusting), increases water infiltration, decreases water and wind erosion, increases the soil’s ability to resist leaching of many plant nutrients, and releases plant nutrients during decomposition.
The planting of cover crops and subsequent incorporation of the green manure into the soil enhances tomato production in Coastal Plains soils. Wheat, oats, rye or ryegrass can be used as winter cover crops. If these non-nitrogen fixing cover crops are to be incorporated as green manure, provide them with adequate nitrogen during their growth. This increases the quantity of organic matter produced and provides a carbon: nitrogen (C:N) ratio less likely to immobilize nitrogen during decomposition.
As a general rule, when non-leguminous organic matter having a C:N ratio exceeding 30 to 1 is incorporated, a supplemental nitrogen application (usually 20 to 30 pounds of nitrogen per acre) prior to incorporation is recommended. The exact rate required will depend on the C:N ratio, soil type and amount of any residual nitrogen in the soil. Plow green manure crops under as deeply as possible with a moldboard plow 4 to 6 weeks prior to installing mulch or transplanting tomatoes.
Planting tomatoes in reduced tillage situations has been tried with variable results in different parts of the country. Often cover crops can be killed with a burn down herbicide. Then tomatoes are either transplanted directly into the cover, or a narrow strip is tilled and prepared for transplanting while leaving the residue between rows. While these residues can protect the fruit from direct contact with the soil, currently the impediments outweigh the benefits for large-scale commercial production. Leguminous covers can provide nitrogen to the crop and there are certainly soil conservation advantages.
The primary encumbrance to success in reduced tillage systems is adequate weed and disease control. The application of phosphates, potash and lime are also more difficult in these systems, so reduced tillage is used only on a limited basis in commercial tomato production. With advances in weed and disease control technology, this type of production may become more feasible in the future.
Crop windbreaks can aid in crop protection and enhance early growth and yield. Frequency or intervals between windbreaks is dictated by distance between tomato rows, spray or harvest alleyway intervals, land availability and equipment characteristics. For instance, bed arrangements may be such that a windbreak is present between every set of four, six or eight beds. Plant windbreaks perpendicular to the prevailing wind direction. When using a taller growing windbreak such as rye, you can expect the windbreak to be effective to a width of about 10 times its height. For instance, with a rye crop that is 3 feet high, the windbreaks can be effective up to 30 feet apart.
In general, close windbreaks give the best wind protection and help moderate the tomato plants’ microenvironment and enhance earliness. Especially on sandy soils, windbreaks reduce damage from sandblasting of plants and small fruit during early spring. Sandblasting can be more of a problem with plastic mulch, as the soil particles are carried easily by the wind across the field. Many growers spread small grain seed after the plastic mulch is applied to reduce sand blasting. Windbreaks also conserve soil moisture by reducing direct evaporation from the soil and transpiration from the plant. This can enhance plant growth throughout the season.
Regardless of the species selected to be used as a windbreak, plant it early enough to be effective as a windbreak by the time tomatoes are transplanted. Establishment of a windbreak crop during the fall or early winter should ensure enough growth for an effective windbreak by spring tomato planting time. Wheat, oats or rye all make good windbreak crops. Windbreaks can be living or non-living. Tomato beds can be established between the windbreaks by tilling only in the bed area.
To minimize insect migration to the tomato crop, destroy windbreak crops by herbicides, mowing and/or tillage before they lose their green color and begin to die back.
Seeding tomatoes directly into the field is not recommended due to the high cost of hybrid seed and the specific conditions required for adequate germination. Most tomatoes are transplanted to the field from greenhouse-grown plants. Direct seeding has other disadvantages: (1) Weed control is usually much more difficult with direct seeded than with transplanted tomatoes; (2) direct seeding requires especially well made seedbeds and specialized planting equipment to adequately control depth of planting and in-row spacing; (3) because of the shallow planting depth required for tomato seed, the field must be nearly level to prevent seeds from being washed away or covered too deeply with water-transported soil; and (4) spring harvest dates will be at least 2 to 3 weeks later for direct seeded tomatoes.
At 59, 68 and 77 degrees F soil temperature, tomato seed require 14, 8 and 6 days, respectively, for emergence when planted ½ inch deep.
Typically, 5- to 6-week old tomato seedlings are transplanted into the field. As with most similar vegetable crops, container-grown transplants are preferred over bare root plants. Container grown transplants retain transplant growing medium (soil-substitute) attached to their roots after removal from the container (flat, tray). Many growers prefer this type transplant because (1) they are less subject to transplant shock, (2) usually require little, if any, replanting, (3) resume growth more quickly after transplanting, and (4) grow and produce more uniformly. Tomato plants produced in a 1-inch cell size tray are commonly used for transplanting. Many growers will use a 1.5-inch cell tray for transplant production in the fall when transplant stress is greater.
Tomato transplants should be hardened off before transplanting to the field. Hardening off is a technique used to slow plant growth prior to field setting so the plant can more successfully transition to the less favorable conditions in the field. This process involves decreasing water for a short period prior to taking the plants to the field. Research shows that reducing temperatures too drastically to harden tomato transplants can induce catfacing in the fruit.
For maximum production, transplants should never have fruits, flowers or flower buds before transplanting. An ideal transplant is young (6 inches to 8 inches tall with a stem approximately ¼ inch to ⅜ inch in diameter), does not exhibit rapid vegetative growth, and is slightly hardened at transplanting time. Rapid growth following transplanting helps assure a well established plant before fruit development. In most cases, it is more economically feasible to have transplants produced by a commercial transplant grower than to grow them on the farm. When purchasing transplants, be sure the plants have the variety name, have been inspected and approved by a plant inspector, and they are of the size and quality specified in the order.
Set transplants as soon as possible after removing from containers or after pulling. If it is necessary to hold tomato plants for several days before transplanting them, keep them cool (around 55-65 degrees F if possible) and do not allow the roots to dry out prior to transplanting. When setting plants, place them upright and place the roots 3 to 4 inches deep. Setting plants at least as deep as the cotyledons has been shown to enhance plant growth and early fruit production and maturity. Completely cover the root ball with soil to prevent wicking moisture from the soil. Tomatoes grow best if nighttime soil temperatures average higher than 60 degrees F.
At transplanting, apply an appropriate fertilizer starter solution (see Fertilizer Management section). After transplanting (especially within the first 2 weeks) it is very important that soil moisture be maintained so that plant roots can become well established.
Tomatoes can be planted in one of many different arrangements that provide adequate space for plant growth. Often the spacing is based on the type of trellising and equipment that will be used in the field. The within-row and between-row spacings are selected to meet these limitations. The optimal plant population per acre may also be influenced by plant growth habit (compact, spreading), plant size at maturity (small, medium, large), vigor of specific cultivars, climate, soil moisture, nutrient availability, management system and soil productivity.
Generally, for production of determinate varieties on plastic mulch, a minimum of 5 feet between rows is used with an in-row spacing of 18 to 24 inches. Six feet between rows is also a popular interval. To space plants 22 inches apart in rows that are 5 feet apart requires 4,760 plants per acre. With 6-foot centers and 18 inches between plants, 4,840 plants are required per acre. Usually a single row of tomatoes is planted down the center of each plastic mulched bed.
On bare ground, space rows 48 to 72 inches apart with 18 inches to 24 inches between plants in the row. For indeterminate types of tomatoes, which produce larger plants, adjust spacing to decrease the population accordingly.
Select varieties on the basis of marketable yield potential, quality, market acceptability, adaptability and disease resistance or tolerance. The selection of a variety(ies) should be made with input from the buyer of the crop several months in advance of planting. Other characteristics to consider include maturity, size, shape, color, firmness, shipping quality and plant habit.
There are a plethora of commercially available tomato varieties, many of which will perform well under Georgia conditions. Varieties will perform differently under various environmental conditions. Yield, though ultimately important, should not be the only selection criteria. Tomatoes produced on plastic mulch with drip irrigation will commonly average more than 1,500 25-pound cartons per acre. Select varieties that have yield potential that equals or surpasses this average.
Plants also need to produce adequate foliage to protect fruit. Basically, a variety must be adaptable to the area, produce a competitive yield and be acceptable to buyers. Disease resistance will be most important with diseases for which there are no other good management options. Varieties produced in Georgia should be resistant to Fusarium wilt (Races 1 and 2) and Verticillium wilt (Race 1). In recent years, resistance to Tomato Spotted Wilt Virus has become equally as important, since varietal resistance is the most effective control method at this time. Other resistance of significance should include Gray Leaf Spot and Tobacco Mosaic Virus.
All commercially important tomatoes grown in Georgia belong to the species Lycopersicon esculentum. Table 1 lists those varieties that have performed well in Georgia or in similar areas of the southeastern United States. Notations in the disease resistance column indicate either resistance or tolerance. Some varieties may not exhibit complete resistance to the disease listed.
Variety
Days to Maturity
Fruit Size
Shape
Disease Resistance
Large Round
F 123 , ST, TSWV, V, FCR
F 12 , GLS, ASC, V
F 12 , GLS, ASC, V
F 123 , ST, FCR, V
F 12 , ASC, GLS, V
F 12 , ASC, GLS, V
F 12 , V, GLS, TYLC
Cherry
Roma/Saladette
F 12 , ST, ASC, V, BS
F = Fusarium Wilt; ST = Stemphylium; TSWV = Tomato Spotted Wilt Virus; V = Verticillium Wilt; FCR = Fruit Cracking; ASC = Ascomycetes; GLS = Gray Leaf Spot, BS = Bacterial Spot; TYLC = Tomato Yellow Leaf Curl
* hot-set varieties.
Most commercial determinate tomatoes are produced using short stake culture for trellising. This type of culture produces fruits that are higher in quality and easier to harvest and enhances spray coverage. In this system, stakes approximately 4 feet long and ¾ to 1 inch square are placed between every one or two plants depending on the tying system that is employed. Stakes are usually driven about 12 inches into the ground. An additional stake can be supplied at the ends of each section to strengthen the trellis.
Stake plants immediately after planting to minimize damage to the root system and to have the trellis ready when needed. Plants are usually tied initially when they are about 12-15 inches tall and should be tied prior to any plants lodging. The first string is usually placed about 10 inches above the ground. Subsequent tyings are placed about 6 inches above the previous one. Determinate varieties may be tied as many as three to four times.
The Florida weave system is one method of tying that is often used. In this system, a stake is placed between every other plant in the row. Twine is then used to tie the plants using a figure eight weave. The twine is wrapped around the stake and is pulled tightly on one side of the first plant and then between the two plants and along the other side of the second plant. At the end of the row or section, the pattern is reversed and, as the twine is wrapped around each stake, the twine is then placed on the other side of each plant going back in the opposite direction along the row. This system uses fewer stakes and encloses the plant with the twine. Subsequent tyings often do not weave between plants but simply go along one side of the plants going one way and the opposite side going the other direction.
Another system of tying involves placing a stake after every plant. The twine is then simply wrapped around each stake and along one side of the plant going along the row and around the other side of the plant coming back in the other direction on the opposite side of the row. Regardless of the system used, the twine should be held with enough tension to adequately support the plants. If the twine is too tight, however, it can impede harvest and damage plants and fruit.
Tomato twine should be resistant to weathering and stretching and should not cut into the plants or fruit. It takes about 30 pounds of synthetic twine per acre for tomatoes. A simple tying tool can be made from conduit or PVC pipe that is 2 to 3 feet long. The twine is passed through the pipe to act as an extension of the worker’s arm. This limits the need to stoop over at each stake to wrap the twine. A similar tool can be made from a wooden dowel or narrow wooden strip. With these, a hole is drilled about 1 inch from each end of the piece of wood and the string passed through each hole. This provides the same extension of the hand as the other method.
Determinate tomatoes often still require some level of pruning. Pruning is the removal of suckers (axillary shoots). The degree to which pruning is needed will vary with the variety used but can impact yield and quality significantly. Plants that produce vigorous foliage that are not pruned will produce more, but smaller fruit. Pruning helps increase the size of the fruit. It can also enhance earliness of the crown set, reduce pest pressure and enhance spray coverage. In general, pruning will involve removal of one to all suckers up to the first fork (the sucker just below the first flower cluster).
Growers should experiment with individual varieties to determine the degree of pruning needed. Often the seed supplier can provide information on specific varieties regarding pruning. Some varieties require only the removal of ground suckers (at the cotyledons) or none at all. Overpruning can cause reduced yields and increased sunburn, blossom end rot and catfacing. More vigorous varieties may require the removal of ground suckers plus two additional suckers. Remove suckers when they are small (2 to 4 inches long). Removal of large suckers is more time consuming and can damage the plant. Prune before the first stringing to facilitate the process, since the strings may be in the way. A second pruning may be required to remove suckers that were not large enough to remove easily during the first pruning and to remove ground suckers that may have developed. Prune plants when the foliage is dry to reduce the spread of disease.
George E. Boyhan and W. Terry Kelley, Extension Horticulturists
Tomato production in Georgia is an expensive, labor intensive endeavor developed to produce high quality fresh market fruit. Because of the cost involved and because early market fruit command higher prices, growers exclusively use transplants to produce tomatoes. Tomato transplant production is a relatively easy but highly specialized function of production. Many growers have neither the greenhouse facilities nor the expertise to undertake transplant production; instead, they will rely on greenhouse growers to produce their transplants. For these growers to ensure a quality supply of transplants, they should contract early with their greenhouse grower to secure plants of the variet(ies) they wish to grow.
Growers should expect to plant between 3,600 and 5,800 plants per acre in a staked tomato operation, depending on the plant spacing. Expect to produce about 4,000 transplants per ounce of seed with approximately 3 ounces required to produce 10,000 seedlings. For example, to produce 10 acres of tomatoes with 5,800 plants per acre would require 58,000 transplants and would require about 18 ounces of seed (rounding up to 60,000 plants). Many seed companies no longer sell seed by weight but by count and will supply the germination rate as well. In such a case, the count and germination rate can be used to estimate the amount of seed to plant to produce the desired number of plants. For example, to produce 58,000 seedlings from seed with 90 percent germination would require 64,445 seed (58,000 divided by 0.90).
Tomato seedlings are usually produced in trays or flats that are divided into cells. Tomatoes require a cell size of approximately 1 inch square to produce a high quality, easily handled transplant. These trays or flats are available in a number of different configurations and sizes. They may be purchased as flats and inserts, polystyrene trays or, more recently, as one-piece rigid polyethylene plastic trays. Growers should make sure the trays or flats used can be handled with their transplanting equipment.
Media for production is usually peat based with various additives such as perlite and vermiculite to improve its characteristics. These can be purchased ready mixed or you can formulate your own mix. The individual components of peat moss, perlite, vermiculite, etc., can be purchased. Whether buying the individual components or a ready-made product, it is advisable to use finer textured media when starting seed. Check with your supplier about media texture. Some media are specially made for this purpose. In addition, these media may have fertilizer and wetting agents mixed in. Media with fertilizer is often referred to as charged.
Treated and/or coated seed may be used to produce seedlings. Most seed is sold with a fungicide applied to the seed. This will help prevent damping off during the germination process. In addition, various seed coats are available, from polymer to clay coats. These are useful when using automated seeding equipment to aid in seed singulation. Plant tomato seed ⅛ to ¼ inch deep. With an automated seeder, the seed will be placed on the surface and will have to be covered, usually with a thin layer of vermiculite.
After flats have been filled and the seed planted, they are often wrapped with plastic pallet wrap or placed in germination rooms (rooms with temperature and humidity tightly controlled) for 48-72 hours to ensure even moisture and temperature for optimum germination. The optimum germination temperature for tomatoes is 85 degrees F, at which tomato seedlings should emerge in about 5-6 days. See Table 2 for soil temperatures and number of days to germination.
