Horticultural Crops - Vegetables

Table of Contents

1. Nutrient Management
2. Pest Management
3. Cole Crops
4. Tomatoes
5. Peppers
6. Field-Seeded Vegetables
7. Summary

Nutrient Management

The most important aspect of nutrient management is to soil test before applying anything. Applying too much fertilizer is expensive and also may affect surface and groundwater. Too little fertilizer may affect yields. Each vegetable crop requires a different fertilizer program. Start by considering the base fertility of your soil. When taking soil samples, be sure to take samples that are represen-tative of the whole field. Good record keeping can help you track a field's fertility over time and assist in making decisions.

Pest Management

Integrated Pest Management helps reduce pesticide use while maintaining yield and quality. See the section on Pest Management in Understanding the Basics for more information.

Cultural Control

• Select the most resistant variety of your crop.
• Select a site that reduces problems.
• Reduce stress and injury to crops. These allow pests to get started.
• Use good sanitation practices. Till under or bury culls.
• Control weeds that may harbour pests.

Chemical Control

When choosing a pesticide, always refer to the pesticide label and consider:

• The days to harvest interval.
• The impact on beneficial insects. For example, consider when honey bees are most active. Bacillus thuringiensis (Bt) is least likely to harm beneficials because it is specific for each type of insect. Synthetic pyrethroids are not persistent but they do affect a broad spectrum of species.
• Use strategies to reduce the chances of pests becoming resistant. Rotate chemical families.

Weather conditions - some pesticides work better under specific environmental conditions. For example, synthetic pyrethroids are most effective in cool temperatures while others such as carbamates and organophosphates work best in warm conditions.

The life cycle of the pest - adult insects are more difficult to control than immature forms. Larger, mature weeds are more difficult to kill.

Cole Crops

The development of an IPM program for cole crops is underway at the Simcoe Research Station. Special attention is being paid to the identification of insect tolerant cultivars. Cultural practices such as trap cropping are being evaluated.

While very limited insect damage may be tolerated on cabbages, consumers will not tolerate any insects on broccoli, cauliflower or brussels sprouts. Particular care must be taken when monitoring these crops for insects.

X = Suitable Control Practice     – = Not Applicable

Tomatoes

Disease control - TOM-CAST is a weather-monitoring program used to time fungicide spray for field tomatoes. A daily disease severity value is determined by the average temperature during hours when foliage is wet. Once the value reaches a certain level, growers should apply fungicide. About 80% of processing tomato growers use TOM-CAST to time their first spray and 50% continue to use the system through the growing season. By following the system throughout the season, growers can usually save between one and three sprays. Further research is underway.

Insect control - the Colorado Potato Beetle can do great damage to tomatoes, particularly when emerging adult beetles attack young plug transplants. While a number of insecticides are available, the beetle is resistant to several of them. This is a particular problem in areas with large acreages of both tomatoes and potatoes. Field rotation can help to reduce CPB pressure.

Figure 3. Potato trap.

Trap cropping can help to reduce pesticide use. Plant strips of potatoes or eggplant, which the insects prefer, at the edges of tomato fields to trap adult beetles. When the beetles are concentrated on the trap crops, apply insecticides to them. The results are fewer sprays on a more concentrated area.

Figure 4. Colorado Potato Beetle

A potato trap for Colorado Potato Beetle control in processing tomatoes allows growers to reduce the number of overall sprays.

Promising research continues into encouraging natural predators, mulching and barrier crops.

Other tomato pests include:

• Flea beetles
• Tarnished plant bugs
• Fruit flies
• Grasshoppers
• Variegated cutworms
  (monitored regionally by OMAF and processors)
• Cabbage loopers
• Aphids
• Hornworms
• Crickets

These pests rarely require treatment. Check OMAF Publication 363 for control measures.

Soil pathogens - high levels of plant parasitic nematodes and Verticillium dahliae cause stunted, wilted, low-yielding tomato plants, especially on sandy soils. To control the problem:

• Rotate crops to avoid pest build-up.
• Plant cover crops such as annual and perennial ryegrass, alfalfa, non-flowering marigolds or work in green material from oilseed radish or mustard to reduce populations. Oats and winter wheat have little effect on populations. Nematode populations increase under clover, corn and many vegetable crops.
• Improve organic matter, drainage and soil structure to promote good root growth.
• Test your fields. Ensure that the samples are representative.
• If threshold levels have been reached, fumigate. Then, concentrate on the other control measures to prevent repeated build-up.

Figure 5. Root lesion nematode.

High levels of plant parasitic nematodes, such as the root lesion nematode, combined with Verticillium dahliae can cause significant yield reductions in tomatoes.

Peppers

European Corn Borer is the major insect pest. Pheromone traps capture males. Traps are monitored regionally and adult flight patterns collected as part of the OMAF Pest Alert program. Check the Agriphone for details. Growers can also put out traps to monitor their own fields. Pests such as aphids and pepper maggots rarely require control, but tarnished plant bugs are becoming more of a problem.

Bacterial spot is the major disease threat. Fixed Copper may reduce the spread of this disease if weather conditions are not too favourable.

Field-Seeded Vegetables

Includes peas, sweet corn, snap beans, cucumbers, carrots, beets, pumpkins, squash, spinach, radish and rutabaga.

Primary pests attacking these vegetables are root-rot organisms and maggots. To reduce the problems:

• Maintain and increase soil organic matter levels.
• Use crop rotation.
• Make sure all seed is treated with fungicide.
• Ensure adequate fertility.
• Improve drainage.
• Ensure good soil structure. Reduce or avoid compaction.

With the trend towards growing supersweet sweet corn for freshmarket, creating good conditions for germination and early growth is critical.

Figure 6. Field of sweet corn.

Summary

There is a saying, "A chain is only as strong as its weakest link." Success in the management of vegetable production is like that chain. Each decision reflects two considerations: short-term viability and long-term sustainability.

Horticultural Crop Production