Extended Field Storage of Processing Tomatoes

Don May, Farm Advisor Emeritus, Fresno County

The objective is to develop a strategy to improve yield of processing tomatoes during periods when high-sustained air temperatures occur and disrupt fruit set, resulting in lower yields to growers. The approach is to plant tomatoes so that fruit set occurs at more desirable temperatures and to test varieties for extended field storage (EFS).

Field Experiments in 2000: The EFS trials consisted of four varieties successful in previous trials and eight new potential varieties. There were two planting dates: March 17th and April 21st. All plots were machine harvested with a commercial crew. Harvest started August 8th for the March planting and August 30th for the April planting. Each trial was harvested four times:

Harvest 1 - fruit was 85-90% ripe
Harvest 2 - two weeks after harvest 1
Harvest 3 - three weeks after harvest 1
Harvest 4 - four weeks after harvest 1

Data: Red fruit from each plot was weighed with a GTO weight mounted dumpster. A five-gallon bucket of unsorted tomatoes was taken from each plot and hand graded for percentage red, green, broken, or rotten, and 50 red fruit were randomly taken for fruit weight. This 50 fruit sample was taken to PTAB for solids and color determinations. About 730 samples were collected from these trials. Additional fruit quality measurements included peeling, pH, brix, color and bostwick.

Results: The top yielding EFS varieties were two previously trialed varieties, H 9492 and H 9665, and two new varieties, H 9995 and H 9992, in both the March and April planting. The Heinz varieties selected for best EFS may not be the best for peeling. These trials show that Bos 3155, Bos 315, and Peto

303 all have good EFS yield for about three weeks. Since these varieties are the most susceptible to poor yields when temperatures are high at fruit set, growers who are required to grow them for peeling will benefit as much from EFS as they will growing Heinz varieties for paste. The three varieties with highest % solids were CXD 199, Bos 315 and Bos 3155, but their yields were also lowest.

Summary of Results: Over three years, trials at West Side Research and Extension Center and grower plantings have shown that selected EFS varieties direct seeded no later than April 21 will give higher yields than late April or May plantings for a September harvest. The results also show that by planting as early as March 15, using EFS varieties, yields will also be higher for late August harvests.

The paste type varieties H 9492, H 9665 and two new ones, H 9992 and H 9995, field stored one month. Peeling type varieties, Bos 3155, Peto 303 and H 9775, will field store two to three weeks. Though their yields are lower, the field-stored yield will be higher than if planted later. In the EFS trials, yields have improved through the third harvest. After the third harvest is where the largest yield losses occur.

At first each grower and processor should work out their own schedule on a limited scale. A strong tomato root system is important for success of this program. Water should be cut off at least two weeks and on some soils up to 30 days before normal harvest. At the university field station 30 days cutoff or more before fruit is 90% ripe has worked best.

For more detailed information about EFS or "heat set" varieties, contact me at the UC West Side Research and Extension Center in Five Points.

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