Knott’s Handbook for Vegetable Growers

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1. Truck farming—Handbooks, manuals, etc. 2. Vegetables—Handbooks, manuals, etc. 3. Vegetable gardening—Handbooks, manuals, etc. I. Title: Handbook for vegetable growers. II. Hochmuth, George J. (George Joseph) III. Knott, James Edward, 1897– Handbook for vegetable growers. IV. Title.

The pace of change in our personal and business lives continues to accelerate at an ever increasing rate. Accordingly, it is necessary to periodically update information in a long-running reference such as Handbook for Vegetable Growers. Our goal in this revision is to provide up-to-date information on vegetable crops for growers, students, extension personnel, crop consultants, and all those concerned with commercial production and marketing of vegetables.

Where possible, information in the Fourth Edition has been updated or replaced with current information. New technical information has been added on World Vegetable Production, Best Management Practices, Organic Crop Production, Food Safety, Pesticide Safety, Postharvest Diseases, and Minimally Processed Vegetables. The Internet has become a valuable source of information since 1997. Hundreds of websites relating to vegetables are included in this edition and are available online at www.wiley.com/college/Knotts.

We are grateful to our colleagues who have provided materials, reviewed portions of the manuscript, and encouraged us in this revision. We especially acknowledge the assistance of Brian Benson, California Asparagus Seed and Transplants, Inc.; George Boyhan, University of Georgia; Wallace Chasson, Florida Department of Agriculture and Consumer Services; Steve Grattan, University of California; Tim Hartz, University of California; Richard Hassell, Clemson University; Larry Hollar, Hollar and Company; Adel Kader, University of California; Tom Moore, Harris-Moran Seed Co.; Stu Pettygrove, University of California; Steven Sargent, University of Florida; Pieter Vandenberg, Seminis Vegetable Seeds; and Jim Watkins, Nunhems USA.

We appreciate the outstanding assistance provided by Wiley editor Jim Harper, Senior Production Editor Millie Torres, and the attention to details and good humor in the preparation of this manuscript by Gail Maynard.

We hope that Handbook for Vegetable Growers will continue to be the timely and useful reference for those with interest in vegetable crops envisioned by Dr. J. E. Knott when it was first published in 1956. James E. Knott (1897–1977) was a Massachusetts native. He earned a B.S. degree at Rhode Island State College and an M.S. and Ph.D. at Cornell University. After distinguished faculty and administrative service at Pennsylvania State College and Cornell University he moved to the University of California, Davis, where he was administrator of the Vegetable Crops Department from 1940 to 1964. The department grew in numbers and stature to be one of the world’s best vegetable centers. Dr. Knott was president of the American Society for Horticultural Science in 1948 and was made a Fellow in 1965.

Oscar A. Lorenz (1914–1994), senior author of the Second Edition (1980) and the Third Edition (1988) of Handbook for Vegetable Growers, was a native of Colorado. He earned a B.S. degree from Colorado State College and a Ph.D. from Cornell University before joining the University of California, Davis faculty in 1941. For the next 41 years he was an esteemed scientist and administrator at both the Riverside and Davis campuses. His research on vegetable crops nutrition was the first to establish the relationship between soil fertility, leaf nutrient composition, and yield. This concept has been used successfully by growers throughout the world. Oscar was recognized as a Fellow of the American Society for Horticultural Science and of the American Society of Agronomy and Soil Science Society of America, and received numerous industry awards. He was a friend to all and a personal mentor to me. (DNM)

01 BOTANICAL NAMES OF VEGETABLES NAMES OF VEGETABLES IN NINE LANGUAGES

02 EDIBLE FLOWERS

03 U.S. VEGETABLE PRODUCTION

04 CONSUMPTION OF VEGETABLES IN THE U.S.

05 WORLD VEGETABLE PRODUCTION

06 NUTRITIONAL COMPOSITION OF VEGETABLES

01 BOTANICAL NAMES OF VEGETABLES

TABLE 1.1. BOTANICAL NAMES, COMMON NAMES, AND EDIBLE PARTS OF PLANTS USED AS VEGETABLES

02 EDIBLE FLOWERS

TABLE 1.3. BOTANICAL NAMES, COMMON NAMES, FLOWER COLOR, AND TASTE OF SOME EDIBLE FLOWERS

03 U.S. VEGETABLE PRODUCTION

TABLE 1.4. U.S. VEGETABLE PRODUCTION STATISTICS: LEADING FRESH MARKET VEGETABLE STATES, 2004¹

TABLE 1.5. IMPORTANT STATES IN THE PRODUCTION OF U.S. FRESH MARKET VEGETABLES BY CROP VALUE, 2004

TABLE 1.6. HARVESTED ACREAGE, PRODUCTION, AND VALUE OF U.S. FRESH MARKET VEGETABLES, 2002–2004 AVERAGE

Adapted from Vegetables, 2004 Summary (USDA, National Agricultural Statistics Service Vg 1–2, 2005), http://jan.mannlib.cornell.edu/reports/nassr/fruit/pvg-bban/vgan0105.pdf.

TABLE 1.9. HARVESTED ACREAGE, PRODUCTION, AND VALUE OF U.S. PROCESSING VEGETABLES, 2002–2004 AVERAGE

TABLE 1.10. IMPORTANT STATES IN THE PRODUCTION OF U.S. PROCESSING VEGETABLES BY CROP VALUE, 2004

Adapted from Vegetables, 2004 Summary (USDA, National Agricultural Statistics Service Vg 1–2, 2005), http://jan.mannlib.cornell.edu/reports/nassr/fruit/pvg-bban/vgan0105.pdf.

TABLE 1.12. U.S. POTATO AND SWEET POTATO PRODUCTION STATISTICS: HARVESTED ACREAGE, YIELD, PRODUCTION, AND VALUE, 2002–2004 AVERAGE

TABLE 1.13. IMPORTANT U.S. STATES IN POTATO AND SWEET POTATO PRODUCTION BY CROP VALUE, 2003

Adapted from Vegetables and Melons Outlook VGS-307 (USDA Economic Research Service, 2005), http://www.ers.usda.gov/publications/vgs/Feb05/vgs307.pdf.

04 VEGETABLE CONSUMPTION

TABLE 1.16. U.S. PER CAPITA CONSUMPTION OF COMMERCIALLY PRODUCED VEGETABLES, 2004

TABLE 1.17. TRENDS IN U.S. PER CAPITA CONSUMPTION OF POTATO, SWEET POTATO, DRY BEAN, AND DRY PEA

05 WORLD VEGETABLE PRODUCTION

Adapted from Vegetables and Melons Situation and Outlook Yearbook VGS-2005 (USDA, Economic Research Service, 2005), http://www.ers.usda.gov/publications/vgs/JulyYearbook2005/VGS2005.pdf.

06 NUTRITIONAL COMPOSITION

01 PLANT GROWING CONTAINERS

02 SEEDS AND SEEDING

03 TEMPERATURE AND TIME REQUIREMENTS

04 PLANT GROWING MIXES

05 SOIL STERILIZATION

06 FERTILIZING AND IRRIGATING TRANSPLANTS

07 PLANT GROWING PROBLEMS

08 CONDITIONING TRANSPLANTS

09 ADDITIONAL INFORMATION SOURCES ON TRANSPLANT PRODUCTION

10 CULTURAL MANAGEMENT

11 CARBON DIOXIDE ENRICHMENT

12 SOILLESS CULTURE

13 NUTRIENT SOLUTIONS

14 TISSUE COMPOSITION

15 ADDITIONAL SOURCES OF INFORMATION ON GREENHOUSE VEGETABLES

TRANSPLANT PRODUCTION

Vegetable crops are established in the field by direct seeding or by use of vegetative propagules (see Part 3) or transplants. Transplants are produced in containers of various sorts in greenhouses, protected beds, and open fields. Either greenhouse-grown containerized or field-grown bare-root transplants can be used successfully. Generally, containerized transplants get off to a faster start but are more expensive. Containerized transplants, sometimes called “plug” transplants have become the norm for melons, pepper, tomato, and eggplant.

Transplant production is a specialized segment of the vegetable business that demands suitable facilities and careful attention to detail. For these reasons, many vegetable growers choose to purchase containerized or fieldgrown transplants from production specialists rather than grow them themselves.

TABLE 2.1. RELATIVE EASE OF TRANSPLANTING VEGETABLES (referring to bare-root transplants) ¹

¹ Although containerized transplant production is the norm for most vegetables, information on bareroot transplants is available at http://pubs.caes.uga.edu/caespubs/pubs/PDF/B1144.pdf (2003).

Organic Vegetable Transplants

Organically grown vegetable transplants are not readily available from most commercial transplant producers. A good source of information on organic transplant production is at http://attra.ncat.org/attra-pub/plugs.html.

For information on organic seed production and seed handling, see J. Bonina and D. J. Cantliffe, Seed Production and Seed Sources of Organic Vegetables (University of Florida Cooperative Extension Service), http://edis.ifas.ufl.edu/hs227.

01 PLANT GROWING CONTAINERS

TABLE 2.2. ADVANTAGES AND DISADVANTAGES OF VARIOUS PLANT GROWING CONTAINERS

Adapted in part from D. C. Sanders and G. R. Hughes (eds.), Production of Commercial Vegetable Transplants (North Carolina Agricultural Extension Service-337, 1984).

02 SEEDS AND SEEDING

SEEDING SUGGESTIONS FOR GROWING TRANSPLANTS

1. Media. Field soil alone usually is not a desirable seeding medium because it may crust or drain poorly under greenhouse conditions. Adding sand or a sand and peat mix may produce a good seeding mixture. Many growers use artificial mixes (see page 65) because of the difficulty of obtaining field soil that is free from pests and contaminating chemicals.

A desirable seeding mix provides good drainage but retains moisture well enough to prevent rapid fluctuations, has good aeration, is low in soluble salts, and is free from insects, diseases, and weed seeds.

2. Seeding. Adjust seeding rates to account for the stated germination percentages and variations in soil temperatures. Excessively thick stands result in spindly seedlings, and poor stands are wasteful of valuable bench or bed space. Seeding into containerized trays can be done mechanically using pelletized seeds. Pelletized seeds are seeds that have been coated with a clay material to facilitate planting by machine. Pelletized seeds also allow for easier singulation (one seed per cell in the tray).

Carefully control seeding depth; most seeds should be planted at 1/4 to 1/2 in. deep. Exceptions are celery, which should only be 1/8 in. deep, and the vine crops, sweet corn, and beans, which can be seeded 1 in. or deeper.

3. Moisture. Maintain soil moisture in the desirable range by thorough watering after seeding and careful periodic watering as necessary. A combination of spot watering of dry areas and overall watering is usually necessary. Do not overwater.

4. Temperature. Be certain to maintain the desired temperature. Cooler than optimum temperatures may encourage disease, and warmer temperatures result in spindly seedlings. Seeded containerized trays can be placed in a germination room where temperature and humidity are controlled. Germination rate and germination uniformity are enhanced with this technique. Once germination has initiated, move the trays to the greenhouse.

5. Disease control. Use disease-free or treated seed to prevent early disease problems. Containers should be new or disease free. A disease-free seeding medium is essential. Maintain a strict sanitation program to prevent introduction of diseases. Carefully control watering and relative humidity. Use approved fungicides as drenches or sprays when necessary. Keep greenhouse environment as dry as possible with air-circulation fans and anti-condensate plastic greenhouse covers.

6. Transplanting. Start transplanting when seedlings show the first true leaves so the process can be completed before the seedlings become large and overcrowded. Seedlings in containerized trays do not require transplanting to a final transplant growing container.

7. Fertilization. Developing transplants need light, water, and fertilization with nitrogen, phosphorus, and potassium to develop a stocky, vigorous transplant, ready for the field. Excessive fertilization, especially with nitrogen, leads to spindly, weak transplants that are difficult to establish in the field. Excessive fertilization of tomato transplants with nitrogen can lead to reduced fruit yield in the field. Only 40–60 ppm nitrogen is needed in the irrigation solution for tomato. Many commercial soilless transplant mixes have a starter nutrient charge, but this charge must be supplemented with a nutrient solution after seedlings emerge.

03 TEMPERATURE AND TIME REQUIREMENTS

TABLE 2.4. RECOMMENDATIONS FOR TRANSPLANT PRODUCTION USING CONTAINERIZED TRAYS

04 PLANT GROWING MIXES

SOILLESS MIXES FOR TRANSPLANT PRODUCTION

Most commercial transplant producers use some type of soilless media for growing vegetable transplants. Most such media employ various mixtures of sphagnum peat and vermiculite or perlite, and growers may incorporate some fertilizer materials as the final media are blended. For small growers or on-farm use, similar types of media can be purchased premixed and bagged. Most of the currently used media mixes are based on variations of the Cornell mix recipe below:

05 SOIL STERILIZATION

Adapted from K. F. Baker (ed.), The UC System for Producing Healthy Container-grown Plants, California Agricultural Experiment Station Manual 23 (1972).

06 FERTILIZING AND IRRIGATING TRANSPLANTS

TABLE 2.8. FERTILIZER FORMULATIONS FOR TRANSPLANT FERTILIZATION BASED ON NITROGEN AND POTASSIUM CONCENTRATIONS

Adapted from P. V. Nelson, “Fertilization,” in E. J. Holcomb (ed.), Bedding Plants IV: A Manual on the Culture of Bedding Plants as a Greenhouse Crop (Batavia, 111.: Ball, 1994), 151–176. Used with permission.

² Moderately higher alkalinity levels are acceptable when lower amounts of limestone are incorporated into the substrate during its formulation. Very high alkalinity levels require acid injection into water source.

³ High hardness values are not a problem if calcium and magnesium concentrations are adequate and soluble salt level is tolerable.

IRRIGATION OF TRANSPLANTS

There are two systems for application of water (and fertilizer solutions) to transplants produced in commercial operations: overhead sprinklers and subirrigation. Sprinkler systems apply water or nutrient solution by overhead water sprays from various types of sprinkler or emitter applicators. Advantages of sprinklers include the ability to apply chemicals to foliage and the ability to leach excessive salts from media. Disadvantages include high investment cost and maintenance requirements. Chemical and water application can be variable in poorly maintained systems, and nutrients can be leached if excess amounts of water are applied. One type of subirrigation uses a trough of nutrient solution in which the transplant trays are periodically floated, sometimes called ebb and flow or the float system. Water and soluble nutrients are absorbed by the media and move upward into the media. Advantages of this system include uniform application of water and nutrient solution to all flats in a trough or basin. Subirrigation with recirculation of the nutrient solution minimizes the potential for pollution because all nutrients are kept in an enclosed system. Challenges with subirrigation include the need for care to avoid contamination of the entire trough with a disease organism. In addition, subirrigation systems restrict the potential to vary nutrient needs of different crops or developmental stages of transplants within a specific subirrigation trough.

With either production system, transplant growers must exercise care in application of water and nutrients to the crop. Excessive irrigation can leach nutrients. Irrigation and fertilization programs are linked. Changes in one program can affect the efficiency of the other program. Excessive fertilization can lead to soluble salt injury, and excessive nitrogen application can lead to overly vegetative transplants. More information on transplant irrigation and the float system is available from:

07 PLANT GROWING PROBLEMS

¹ Possible causes are listed here; however, more than one factor may lead to the same symptom. Therefore, plant producers should thoroughly evaluate all possible causes of a specific disorder.

SUGGESTIONS FOR MINIMIZING DISEASES IN VEGETABLE TRANSPLANTS

Successful vegetable transplant production depends on attention to disease control. With the lack of labeled chemical pesticides, growers must focus on cultural and greenhouse management strategies to minimize opportunities for disease organisms to attack the transplant crop.

Greenhouse environment: Transplant production houses should be located at least several miles from any vegetable production field to avoid the entry of disease-causing agents in the house. Weeds around the greenhouse should be removed and the area outside the greenhouse maintained free of weeds, volunteer vegetable plants, and discarded transplants.

Media and water: All media and irrigation water should be pathogen free. If media are to be blended on site, all mixing equipment and surfaces must be routinely sanitized. Irrigation water should be drawn from pathogenfree sources. Water from ponds or recycling reservoirs should be avoided.

Planting material: Only pathogen-free seed or plant plugs should be brought into the greenhouse to initiate new transplant crops. Transplant producers should not accept seeds of unknown quality for use in transplant production. This can be a problem, especially when producing small batches of transplants from small packages of seed, e.g., for a variety trial.

Cultural practices: Attention must be given to transplant production practices such as fertilization, irrigation, and temperature so that plant vigor is optimum. Free moisture, from sprinkler irrigation or condensation, on plants should be avoided. Ventilation of houses by exhaust fans and horizontal airflow fans helps reduce free moisture on plants. Growers should follow a strict sanitation program to prevent introduction of disease organisms into the house. Weeds under benches must be removed. Outside visitors to the greenhouse should be strictly minimized, and all visitors and workers should walk through a disinfecting foot bath. All plant material and soil mix remaining between transplant crops should be removed from the house.

CONTROLLING TRANSPLANT HEIGHT

One aspect of transplant quality involves transplants of size and height that are optimum for efficient handling in the field during transplantation and for rapid establishment. Traditional means for controlling plant height included withholding water and nutrients and/or application of growth regulator chemicals. Today, growth regulator chemicals are not labeled for vegetable transplant production. Plant height control research focuses on nutrient management, temperature manipulation, light quality, and mechanical conditioning of plants.

Nutrient management: Nitrogen applied in excess often causes transplants to grow tall rapidly. Using low-N solutions with 30–50 parts per million (ppm) nitrogen helps control plant height when frequent (daily) irrigations are needed. Higher concentrations of N may be needed when irrigations are infrequent (every 3 to 4 days). Often, an intermediate N concentration (e.g., 80 ppm) is chosen for the entire transplant life cycle, and an excessive growth rate often results. Irrigation frequency should guide the N concentration. Research has shown that excessive N applied to the transplant can lead to reduced fruit yield in the field.

Moisture management: Withholding water is a time-tested method of reducing plant height, but transplants can be damaged by drought. Sometimes transplants growing in Styrofoam trays along the edge of a greenhouse walkway dry out faster than the rest of the transplants in the greenhouse. These dry plants are always shorter compared to the other transplants. Overwatering transplants should therefore be avoided, and careful attention should be given to irrigation timing.

Light intensity: Transplants grown under reduced light intensity stretch; therefore, growers must give attention to maximizing light intensity in the greenhouse. Aged polyethylene greenhouse covers should be replaced and greenhouse roofs and sides should be cleaned periodically, especially in winter. Supplementing light intensity for some transplant crops with lights may be justified.

Temperature management: Transplants grown under cooler temperatures (e.g., 50°F) are shorter than plants grown under warmer temperatures. Where possible, greenhouse temperatures can be reduced or plants moved outdoors. Under cool temperatures, the transplant production cycle is longer by several days and increased crop turnaround time may be unacceptable. For some crops, such as tomato, growing transplants under cool temperatures may lead to fruit quality problems, e.g., catfacing of fruits.

Mechanical conditioning: Shaking or brushing transplants frequently results in shorter transplants. Transplants can be brushed by several physical methods—for example, by brushing a plastic rod over the tops of the plants. This technique obviously should be practiced on dry plants only to avoid spreading disease organisms.

Day/night temperature management: The difference between the day and night temperatures (DIF) can be employed to help control plant height. With a negative DIF, day temperature is cooler than night temperature. Plants grown with a positive DIF are taller than plants grown with a zero or negative DIF. This system is not used during germination but rather is initiated when the first true leaves appear. The DIF system requires the capability to control the greenhouse temperature and is most applicable to temperate regions in winter and spring, when day temperatures are cool and greenhouses can be heated.

TABLE 2.12. VEGETABLE TRANSPLANT RESPONSE TO THE DIFFERENCE IN DAY AND NIGHT TEMPERATURE (DIF)

From E. J. Holcomb (ed.), Bedding Plants IV (Batavia, Ill.: Ball, 1994). Original source: J. E. Erwin and R. D. Heins, “Temperature Effects on Bedding Plant Growth,” Bulletin 42:1–18, Minnesota Commercial Flower Growers Association (1993). Used with permission.

08 CONDITIONING TRANSPLANTS

Objective: To prepare plants to withstand stress conditions in the field. These may be low temperatures, high temperatures, drying winds, low soil moisture, or injury to the roots in transplanting. Growth rates decrease during conditioning, and the energy otherwise used in growth is stored in the plant to aid in resumption of growth after transplanting. Conditioning is used as an alternative to the older term, hardening.

Methods: Any treatment that restricts growth increases hardiness. Coolseason crops generally develop hardiness in proportion to the severity of the treatment and length of exposure and when well-conditioned withstand subfreezing temperatures. Warm-season crops, even when highly conditioned, do not withstand temperatures much below freezing.

1. Water supply. Gradually reduce water by watering lightly at less frequent intervals. Do not allow the plants to dry out suddenly, with severe wilting.

2. Temperature. Expose plants to lower temperatures (5–10°F) than those used for optimum growth. High day temperatures may reverse the effects of cool nights, making temperature management difficult. Do not expose biennials to prolonged cool temperatures, which induces bolting.

3. Fertility. Do not fertilize, particularly with nitrogen, immediately before or during the initial stages of conditioning. Apply a starter solution or liquid fertilizer 1 or 2 days before field setting and/or with the transplanting water (see page 78).

4. Combinations. Restricting water and lowering temperatures and fertility, used in combination, are perhaps more effective than any single approach.

Duration: Seven to ten days are usually sufficient to complete the conditioning process. Do not impose conditions so severe that plants are overconditioned in case of delayed planting because of poor weather. Overconditioned plants require too much time to resume growth, and early yields may be lower.

PRETRANSPLANT HANDLING OF CONTAINERIZED TRANSPLANTS

Field performance of transplants is related not only to production techniques in the greenhouse but also to handling techniques before field planting. In the containerized tray production system, plants can be delivered to the field in the trays if the transplant house is near the production fields. For long-distance transport, the plants are usually pulled from the trays and packed in boxes. Tomato plants left in trays until field planting tend to have more rapid growth rates and larger fruit yields than when transplants were pulled from the trays and packed in boxes. Storage of pulled and packed tomato plants also reduces yields of large fruits compared to plants kept in the trays. If pulled plants must be stored prior to planting, storage temperatures should be selected to avoid chilling or overheating the transplants. Transplants that must be stored for short periods can be kept successfully at 50–55°F.

09 ADDITIONAL INFORMATION SOURCES ON TRANSPLANT PRODUCTION

Charles W. Marr, Vegetable Transplants (Kansas State University, 1994), http://www.oznet.ksu.edu/library/hort2/MF1103.pdf.

W. Kelley et al., Commercial Production of Vegetable Transplants (University of Georgia, 2003), http://pubs.caes.uga.edu/caespubs/pubcd/b1144.htm.

J. Bodnar and R. Garton, Growing Vegetable Transplants in Plug Trays (Ontario Ministry of Agriculture, Food, and Rural Affairs, 1996), http://www.omafra.gov.on.ca/english/crops/facts/96-023.htm.

L. Greer and K. Adam, Organic Plug and Transplant Production (2002), http://attra.ncat.org/attra-pub/plugs.html

D. Krauskopf, Vegetable Transplant Production Tips (Michigan State University), http://www.horticulture.wisc.edu/freshveg/Publications/WFFVGC%202005/Vegetable%20Transplant%20Production%20Tips.doc.

R. Styer and D. Koranski, Plug and Transplant Production: A Grower’s Guide (Batavia, Ill.: Ball).

GREENHOUSE CROP PRODUCTION

10 CULTURAL MANAGEMENT

CULTURAL MANAGEMENT OF GREENHOUSE VEGETABLES

Although most vegetables can be grown successfully in greenhouses, only a few are grown there commercially. Tomato, cucumber, and lettuce are the three most commonly grown vegetables in commercial greenhouses. Some general cultural management principles are discussed here.

Greenhouse Design

Successful greenhouse vegetable production depends on careful greenhouse design and construction. Consideration must be provided for environmental controls, durability of components, and ease of operations, among other factors. The publications listed at the end of this chapter offer helpful advice for construction.

Sanitation

There is no substitute for good sanitation for preventing insect and disease outbreaks in greenhouse crops.

To keep greenhouses clean, remove and destroy all dead plants, unnecessary mulch material, flats, weeds, etc. Burn or bury all plant refuse. Do not contaminate streams or water supplies with plant refuse. Weeds growing in and near the greenhouse after the cropping period should be destroyed. Do not attempt to overwinter garden or house plants in the greenhouses. Pests can also be maintained and ready for an early invasion of vegetable crops. To prevent disease organisms from carrying over on the structure of the greenhouse and on the heating pipes and walks, spray with formaldehyde (3 gal 37% formalin in 100 gal water). Immediately after spraying, close the greenhouse for 4–5 days, then ventilate. Caution: Wear a respirator when spraying with formaldehyde.

A 15–20-ft strip of carefully maintained lawn or bare ground around the greenhouse helps decrease trouble from two-spotted mites and other pests. To reduce entry of whiteflies, leafhoppers, and aphids from weeds and other plants near the greenhouses, spray the area growth occasionally with a labeled insecticide and control weeds around the greenhouse. Some pests can be excluded with properly designed screens.

Monitoring Pests

Insects such as greenhouse and silverleaf whiteflies, thrips, and leaf miners are attracted to shades of yellow and fly toward that color. Thus, insect traps can be made by painting pieces of board with the correct shade of yellow pigment and then covering the paint with a sticky substance. Similar traps are available commercially from several greenhouse supply sources. By placing a number of traps within the greenhouse range, it is possible to check infestations daily and be aware of early infestations. Control programs can then be commenced while populations are low.

Two-spotted mites cannot be trapped in this way, but infestations usually begin in localized areas. Check leaves daily and begin control measures as soon as the first infested areas are noted.

Spacing

Good-quality container-grown transplants should be set in arrangements to allow about 4 sq ft/plant for tomato, 5 sq ft/plant for American-type cucumber, and 7–9 sq ft/plant for European-type cucumber. Lettuce requires 36–81 sq in./plant.

Temperature

Greenhouse tomato varieties may vary in their temperature requirements, but most varieties perform well at a day minimum temperature of 70–75°F and a night minimum temperature of 62–64°F. Temperatures for cucumber seedlings should be 72–76°F day and 68°F night. In a few weeks, night temperature can be gradually lowered to 62–64°F. Night temperatures for lettuce can be somewhat lower than for tomato and cucumber.

In northern areas, provisions should be made to heat water to be used in greenhouses to about 70°F.

Pruning and Tying

Greenhouse tomatoes and cucumbers are usually pruned to a single stem by frequent removal of axillary shoots or suckers. Other pruning systems are possible and sometimes used. Various tying methods are used; one common method is to train the pruned plant around a string suspended from an overhead wire.

Pollination

Greenhouse tomatoes must be pollinated by hand or with bumblebees to assure a good set of fruit. This involves tapping or vibrating each flower cluster to transfer the pollen grains from the anther to the stigma. This should be done daily as long as there are open blossoms on the flower cluster. The pollen is transferred most readily during sunny periods and with the most difficulty on dark, cloudy days. The electric or batteryoperated hand vibrator is the most widely accepted tool for vibrating tomato flower clusters. Most red-fruited varieties pollinate more easily than pinkfruited varieties and can often be pollinated satisfactorily by tapping the overhead support wires or by shaking flowers in the airstream of a motordriven backpack air-blower. Modern growers now use bumblebees for pollinating tomato. Specially reared hives of bumblebees are purchased by the grower for this purpose.

Crop	Yield (cwt/acre)
Artichoke¹	122
Asparagus¹	31
Bean, snap	62
Broccoli¹	146
Cabbage	317
Cantaloupe	244
Carrot	311
Cauliflower¹	163
Celery¹	693
Cucumber	181
Garlic¹	172
Honeydew melon	223
Lettuce, head	371
Lettuce, leaf	244
Lettuce, romaine	315
Onion	452
Pepper, bell¹	299
Pepper, chile¹	142
Pumpkin¹	211
Spinach	152
Squash¹	156
Strawberry¹	423
Sweet corn	114
Tomato	295
Watermelon	259

Crop	Yield (tons/acre)
Bean, lima	1.29
Bean, snap	3.97
Carrot	27.02
Cucumber	5.07
Pea, green	1.86
Spinach	9.44
Sweet corn	7.44
Tomato	37.20

Rank	Potato	Sweet Potato
1	Idaho	North Carolina
2	Washington	California
3	California	Louisiana
4	Wisconsin	Mississippi
5	Colorado	Alabama

Country	Production (million cwt)	(%)
China	8,988.1	48.9
India	1,697.3	9.2
United States	823.6	4.5
Turkey	552.5	3.0
Russian Federation	326.0	1.7
Italy	325.5	1.7
Others	5,622.5	31.0
World	18,351.3	100.0

Easy	Moderate	Require Special Care²
Beet	Celery	Sweet corn
Broccoli	Eggplant	Cantaloupe
Brussels sprouts	Onion	Cucumber
Cabbage	Pepper	Summer squash
Cauliflower		Watermelon
Chard
Lettuce
Tomato

Container	Advantages	Disadvantages
Single peat pellet	No media preparation, low storage requirement	Requires individual handling in setup, limited sizes
Prespaced peat pellet	No media preparation, can be handled as a unit of 50	Limited to rather small sizes
Single peat pot	Good root penetration, easy to handle in field, available in large sizes	Difficult to separate, master container is required, dries out easily, may act as a wick in the field if not properly covered
Strip peat pots	Good root penetration, easy to handle in field, available in large sizes, saves setup and filling time	May be slow to separate in the field, dries out easily
Plastic flat with unit	Easily handled, reusable, good root penetration	Requires storage during off season, may be limited in sizes
Plastic pack	Easily handled	Roots may grow out of container causing handling problems, limited in sizes, requires some setup labor
Plastic pot	Reusable, good root penetration	Requires handling as single plant
Polyurethane foam flat	Easily handled, requires less media than similar sizes of other containers, comes in many sizes, reusable	Requires regular fertilization, plants grow slowly at first because cultural systems use low levels of nitrogen
Expanded polystyrene tray	Lightweight, easy to handle, various cell sizes and shapes, reusable, automation compatible	Need sterilization between uses, moderate investment, as trays age, roots can penetrate sidewalls of cells
Injection-molded trays	Various cell sizes, reusable, long life, compatible for automation	Large investment, need sterilization between uses
Vacuum-formed tray	Low capital investment	Short life span, needs sterilization between uses, automation incompatible due to damage to tray

Vegetable	Plants/oz Seed	Seed Required to Produce 10,000 Transplants
Asparagus	550	1¼ lb
Broccoli	5,000	2 oz
Brussels sprouts	5,000	2 oz
Cabbage	5,000	2 oz
Cantaloupe	500	1¼ lb
Cauliflower	5,000	2 oz
Celery	15,000	1 oz
Sweet corn	100	6¼ lb
Cucumber	500	11/4 lb
Eggplant	2,500	4 oz
Lettuce	10,000	1 oz
Onion	4,000	3 oz
Pepper	1,500	7 oz
Summer squash	200	3¼ lb
Tomato	4,000	3 oz
Watermelon	200	3¼ lb

Agent	Method	Recommendation
Heat	Steam	30 min at 180°F
	Aerated steam	30 min at 160°F
	Electric	30 min at 180°F
Chemical	Chloropicrin	3–5 cc/cu ft of soil. Cover for 1–3 days. Aerate for 14 days or until no odor is detected before using.
	Vapam	1 qt/100 sq ft. Allow 7–14 days before use.
	Methyl bromide	The phase-out of methyl bromide: http://www.epa.gov/spdpublc/mbr/
Caution: Chemical fumigants are highly toxic. Follow manufacturer’s recommendations on the label.
Soluble salts, manganese, and ammonium usually increase after heat sterilization. Delay using heat-sterilized soil for at least 2 weeks to avoid problems with these toxic materials.

Pests	30-min Temperature (°F)
Nematodes	120
Damping-off organisms	130
Most pathogenic bacteria and fungi	150
Soil insects and most viruses	160
Most weed seeds	175
Resistant weeds and resistant viruses	212

Variable	Plug Production	Finish Flats and Pots
pH¹ (acceptable range)	5.5–7.5	5.5–7.5
Alkalinity²	1.5 me/L (75 ppm)	2.0 me/L (100 ppm)
Hardness³	3.0 me/L (150 ppm)	3.0 me/L (150 ppm)
EC	1.0 mS	1.2 mS
Ammonium-N	20 ppm	40 ppm
Boron	0.5 ppm	0.5 ppm

Symptoms	Possible Causes¹	Corrective Measures
1. Spindly growth	Shade, cloudy weather, excessive watering, excessive temperature	Provide full sun, reduce temperature, restrict watering, ventilate or reduce night temperature, fertilize less frequently, provide adequate space.
2. Budless plants	Many possible causes; no conclusive cause	Maintain optimum temperature and fertilization programs.
3. Stunted plants	Low fertility	Apply fertilizer frequently in low concentration.
A. Purple leaves	Phosphorus deficiency	Apply a soluble, phosphorus-rich fertilizer at 50 ppm P every irrigation for up to 1 week
B. Yellow leaves	Nitrogen deficiency	Apply N fertilizer solution at 50–75 ppm each irrigation for 1 week. Wash the foliage with water after application.
C. Wilted shoots	Pythium root rot, flooding damage, soluble salt damage to roots	Check for Pythium or other disease organism. Reduce irrigation amounts and reduce fertilization.
D. Discolored roots	High soluble salts from overfertilization; high soluble salts from poor soil sterilization	Leach the soil by excess watering. Do not sterilize at temperatures above 160°F. Leach soils before planting when soil tests indicate high amounts of soluble salts.
E. Normal roots	Low temperature	Maintain suitable day and night temperatures.
4. Tough, woody plants	Overhardening	Apply starter solution (10-55-10 or 15-30-15 at 1 oz/gal to each 6–12 sq ft bench area) 3–4 days before transplanting.
5. Water-soaked and decayed stems near the soil surface	Damping off	Use a sterile, well-drained medium. Adjust watering and ventilation practices to provide a less moist environment. Use approved fungicidal drenches.
6. Poor root growth	Poor soil aeration; poor soil drainage; low soil fertility; excess soluble salts; low temperature; residue from chemical sterilization; herbicide residue	Determine the cause and take corrective measures.
7. Green algae or mosses growing on soil surface	High soil moisture, especially in shade or during cloudy periods	Adjust watering and ventilation practices to provide a less moist environment. Use a better-drained medium.

Common Name	Response to DIF¹
Broccoli	3
Brussels sprouts	3
Cabbage	3
Cantaloupe	3
Cucumber	1–2
Eggplant	3
Pepper	0–1
Squash	2
Tomato	2
Watermelon	3

Materials	Quantity to Use in Transplanter Tank
Readily Soluble Commercial Mixtures
8-24-8, 11-48-0	(Follow manufacturer’s directions.)
23-21-17, 13-26-13	Usually 3 lb/50 gal water
6-25-15, 10-52-17
Straight Nitrogen Chemicals
Ammonium sulfate, calcium nitrate, or sodium nitrate	21/2 lb/50 gal water
Ammonium nitrate	11/2 lb/50 gal water
Commercial Solutions
30% nitrogen solution	11/2 pt/50 gal water
8-24-0 solution (N and P₂O₅)	2 qt/50 gal water
Regular Commercial Fertilizer Grades
4-8-12, 5-10-5, 5-10-10, etc.
1 lb/gal for stock solution; stir well and let settle	5 gal stock solution with 45 gal water