Tomato Varieties
Many varieties exist on the market for South Florida and more specific information on individual varieties is available from county extension specialists and private seed companies. Varieties noted here are generic and prevalent in the state. They illustrate how some aspects of varietal selection management can be tailored according to different climate forecasts.
In dry, warm weather, typical of La Niña years, viruses caused by thrips (Tomato Spotted Wilt [TSW]) and white fly (Tomato Yellow Leaf Curl [TYLCV]) are problems. In El Niño years, soil-borne fungal problems and Fusarium races 1, 2, and 3 are exacerbated by wet weather. In cool, wet winters. Gray wall, blotching, and other fruit quality problems tend to increase. Cloudy, cool, rainy or foggy weather, and/or excess nitrogen conditions greatly increase fruit damage.
The variety to plant is typically decided upon several months in advance in order to secure seed and arrange for transplant production. This is one reason why an advanced forecast of the upcoming season might be useful to growers. If a La Niña is forecast, more hot-set varieties could be planted. If an El Niño is forecast Fusarium tolerant varieties might be preferred. When a different seasonal climate is expected but surrounded by much uncertainty, varieties that concentrate fruit set on first pick might be preferred. The following table may help as a simple guide as to how some varieties behave under seasonal climate variability:
| El Nino Phase | Production Season | ||
|---|---|---|---|
| Oct-Dec | Jan-Mar | Jul-Sept | |
| El Niño | Use varieties tolerant to Fusarium races 1, 2 & 3; and soil-borne fungal problems. | Use varieties tolerant to Fusarium races 1, 2 & 3 and soil-borne fungal problems. | Use varieties tolerant to diseases transmitted by thrips and white fly (TYLCV). |
| La Nina | Use varieties tolerant to diseases transmitted by thrips and white fly (TYLCV). Hot Sets for early plantings. | Use varieties tolerant to diseases transmitted by thrips and white fly (TYLCV). Hot Sets for most plantings, especially later ones. Varieties that concentrate fruit set on first pick. Fungal disease resistance is not as important a criterion as usual. | No climate-based recommendation. |
| Neutral | No climate-based recommendation. | No climate-based recommendation. | No climate-based recommendation. |
Pests and Diseases
Bacterial and fungal diseases are typically associated with wet climates as can be expected in neutral and El Niño years. Some cultivars are more tolerant than others to diseases such as bacterial spot, including FL47 and FL91 types. The whitefly is a vector of tomato yellow leaf curl virus (TYLCV) and causes irregular ripening. Currently, some varieties exist that are somewhat more tolerant to TYLCV. Many of these varieties were developed in arid climates and do not perform as well under certain Florida environmental conditions, especially during El Niño (rainy, cool) phases.
White flies are a desert insect and reproduce rapidly in dry weather. Higher temperatures also impact disease transmission during dry conditions, typical of La Niña years. Due to the magnitude of the white fly outbreak in Florida in recent years, researchers are encouraging growers to maintain a crop or host free period of at least six weeks in summer.
In the Manatee-Ruskin area virus outbreaks are greater in the fall, and can be expected to be even worse in La Niña years.. Early plantings should be virus-tolerant cultivars; however, even these varieties can act as symptomless hosts, meaning whitefly controls should still be used. In Immokalee, the same is true for spring when populations may explode as early as February. The last plantings in spring should be with virus/white fly-tolerant varieties.
Heat Tolerance
When a hot, dry season with nighttime temperatures above 65°F is likely to occur because of a La Niña phase forecast, hot set varieties are a good choice. Hot sets have a wider range of adaptability but the plants are not as vigorous or tolerant to bacteria. Rough shoulders and blossom scars occur more frequently in these varieties in cold weather, such as in El Niño years. When La Niña is forecast plantings should be concentrated on early fruit sets.
Yields and Fruit Quality
Although few major differences exist in yield among major varieties used, some variability can be attributed to climate during the growing season. Yields may vary according to how a variety handles climate and how concentrated the fruit set is. Growers might select a variety that has a greater fruit set for the first pick if there is a variation in climate forecast for the upcoming season. Adjusting planting date during El Niño or La Niña phase is one of the most manageable responses to seasonal forecasts. See Count Yield Forecast for more information on this subject.
Another factor that might be influenced by climate is flavor; climate could be important for superior quality tomatoes, especially now that more tomatoes are being harvested at breaker color. Rain is problematic when harvesting ripe tomatoes. Precautions can be taken to find the best odds for drier conditions at harvest by using the yield probabilities available in the County Yield Forecast. A variety harvested later could make more profit and offset yield reduction. However, late harvesting requires different handling and marketing than mature green tomatoes. Market and climate-based decisions must be considered and balanced in this case.
Land Preparation
Climate-based land preparation management changes are a difficult option for producers. If producers expect a wetter fall because an El Niño is coming, deeper ditches can be dug in some production regions. This is a common practice in some areas and is only marginally more expensive. In other areas, ditches are often dug to a depth correlated to bed height and digging deeper ditches might make water management more difficult, especially for seepage-irrigated fields. Applications of herbicide to ditches would be too extreme a measure because erosion problems might outweigh the benefits of improved drainage. Sediment and pesticide runoff can be major problems and will become even more scrutinized under TMDL guidelines and must be taken into consideration.
For most producers, bed height is standard, as equipment is fixed and expensive. For those who can adjust bed height, higher beds are a good option for wet El Niño years, Care must be taken in water management to avoid going from very wet to very dry. In Homestead, for example, beds would have to be higher and narrower because there is a finite amount of soil.
Fertilization
Fertilization practices are only slightly changeable based upon seasonal climate forecasts. Fertilizer is not expensive and is often used at higher than IFAS recommendations. If a wetter, cooler season is forecast because of an El Niño phase growers might increase the percentage of slow release fertilizer in their program. Approximately 70% of producers use drip irrigation and 'spoon-feed' fertilizer to the plants, thus the ability to make adjustments in fertilizer applications is already in place. Growers utilizing seep irrigation might actually increase fertilizer amounts if a wet, El Niño driven season were predicted, but this would not be recommended due to potential leaching consequences. In very rainy years (El Niño), leaching can be high. Growers might add more fertilizer or change to slow release.
Fresh Tomato Insurance
Managing farm risk is complicated for a host of reasons. Growers do not manage climate risk in isolation but rather as part of more comprehensive strategies that also consider risks posed by price fluctuations and policy changes. Crop insurance agents and other agri-business specialists listed in the USDA/RMA agent locator can assist farmers in developing a good management plan. Risk management tools, such as climate information and crop insurance, often work best when they are used together.
USDA's Risk Management Agency (RMA) web site is the best source to learn more about the different types of crop insurance available to tomato growers. Essentially, there are two types of products:
Some 178 MPCI (Multiple Peril Insurance Program) and DOL (Dollar Plan) policies were sold to Florida tomato growers in 2003 and protected more than 27,000 acres, or about 60% of the 2002 planted acreage of 45,000 acres. USDA/RMA cautions growers to carefully consider how a crop insurance policy will work in conjunction with their other risk management tools to achieve the best possible outcome.