The '97 Crop

This year's prune crop is heavy both locally and statewide; worldwide prune supplies are predicted to increase by 75,000 tons this year. Only large, good quality prunes will be profitable this season.

Prune Bargaining Association Moves to
Improve Overall Quality, Correct Supply

Yuba City, CA, June 27, 1997 -- Hoping to improve the overall quality of California's prune supply, the Prune Bargaining Association (PBA) recently voted to pursue a program that eliminates undersize fruit. The move is expected to send a quality message to growers and packers by eliminating 24 screen fruit (fruit smaller than 24/32 inches in diameter). Excluding this small fruit from production is also expected to reduce burdensome surpluses caused by bumper crops and mounting international surpluses.

The unanimously adopted PBA resolution calls on the grower-owned association to use its influence to put a 24 screen undersize program in place under the federal marketing order. Presently the PBA is working with packers and other industry leaders to unify the entire industry behind this quality enhancing measure.

"Growers are in favor of eliminating the 24 screen," asserts PBA General Manager Greg Thompson. "The PBA action reflects a grassroots call among independent and cooperative growers to improve quality and correct the supply situation."

A federal marketing order establishes the prune industry's quality standards. It would require action by the United States Department of Agriculture to eliminate 24 screen fruit. In addition to driving quality standards down, the PBA is concerned that 24 screen fruit, which averages 125 prunes per pound and can only be used by blending with larger prunes, has inflated surplus reports and artifically driven prune prices and markets down.

The Prune Bargaining Association was formed in 1968 as a grower-owned cooperative to improve the economy of the California prune industry, encourage the production of a quality product and provide a forum for growers to exchange ideas regarding the industry. The PBA establishes the industry's raw product prices for prunes.

Harvest Strategies to Minimize Small Fruit

Harvest management will be your last chance to minimize worthless or small, non-profitable fruit.

Maturity and fruit quality: French prunes are mature and should be harvested when the average flesh pressure of the fruit has softened to 3-4 pounds. At this time, the fruits have reached their maximum sugar content and when dried will yield the highest tonnage (lowest dry ratio) of best quality (largest) prunes.

Harvest timing based on these known physiological changes in the fruit can substantially affect income per acre. Harvesting before fruit are mature results in a high "dry ratio" due to lower sugar content, thus smaller fruit and less dry yield per acre result. French prunes remain in optimal condition for harvest approximately seven to ten days. Following this period fruit drop becomes excessive and dried fruit quality is reduced as voids and gas pockets develop in the flesh.

Fruit size and crop size: Small fruit size can be anticipated where heavy crops exist. Physically, too many fruit cause low sugar content resulting in poor dry away, thus small fruit sizes. For heavy cropped orchards allow maximum sugar to develop and thus best possible dry away to benefit fruit size before harvesting (this occurs as fruit reach 3-4 lbs flesh pressure). Usually, the best strategy for heavy crops means delaying harvest, allowing some natural fruit drop to occur.

By using this strategy the grower sustains the fruit drop loss, but loss from high dry away, that means harvesting and processing more worthless fruit, is minimized, resulting in a more valuable crop at lower cost per dry ton.

Note: It is not always possible to harvest at the optimal time due to equipment and acreage limitations; usually one must begin harvest early and continue later than the optimal period. However, it will be of benefit to plan your harvest to coincide with optimal maturity as best you can this year.

ALSO REMEMBER to coordinate your harvest program with your dryer manager_his prorate restrictions and your harvesting capabilities are different.

Field sizing involves the use of a chain or bar sizer on the harvester to eliminate low value (non-profitable) or worthless prunes in the field, avoiding the expense of hauling and drying these fruit.

Predicting the need for field sizing: The table at the end of this newsletter (Claypool circa 1965) was developed from data collected in numerous orchards to predict dry fruit size based on fresh fruit size and soluble solids just prior to harvest. In 1996, subsequent samplings by UC farm advisors to verify Claypool's findings have shown that, although some error exists in Claypool's figures, his chart can be useful to predict your ultimate average dried fruit size. Your need to field size can be determined from this table.

Predicting dry count/lb: Take several 100 fruit samples (take 20 fruits from 5 trees being sure to sample both fruit clusters inside and outside of the tree at eye level) from each orchard.

1. Weigh each fresh sample.
   
2. Divide the number of fruit in each sample (100) by the weight of the sample (in lbs) to determine number of fruit per pound.
   
3. Determine percent soluble solids (best way is to puree halves of all fruit from a sample in a blender and filter drops of juice onto a refractometer). Ask your field man or dryer to help if you do not own a refractometer.
   
4. Average the fresh count and soluble solids values for all samples to determine the orchard average. Different areas in the orchard could be treated separately if differences in crop exist that may require different harvest strategies.
   
5. Use table to predict your dry count/lb based on your average fresh count/lb and soluble solids for the orchard. To predict drying ratio, divide the predicted dry count/lb by the fresh count/lb.
   

If field sizing appears to be necessary, a chain or bar size from 1 inch to 1-1/8 inch is normally used. This year larger chain sizes may be needed to ensure more small fruit is dropped in the field (see below).

Remember, the Claypool tables are not perfect and they fall short where fruit have soluble solids below 16%. Nevertheless, they help in making the field sizing decision.

Field sizing is not for everyone. Consider these:

1. Crop size: Field sizing is best used where heavy crops occur and a high percentage of undersized fruit exists. As a minor amount of "good fruit" is always lost with field sizing, low to moderate crops do not benefit by sorting a low amount of small prunes out. In fact, value lost from good fruit may outweigh benefit gained from eliminating small ones in lightly cropped orchards.
   
2. Chain size: Chain (screen) size, or bar space, influences the size of fruit eliminated in the field. We have only used spaces up to 1-1/8" in diameter. In general, recommended sizes range from a 1" to 1-1/8" opening. However, this season, due to need to sort out even bigger fruit, wider spacings may prove beneficial. Harvest timing (see below) affects the decision on chain size.
   
3. Harvest timing: Prunes accumulate sugar (soluble solids) during the ripening process. Early in the harvest period, when sugars are relatively low, "dry away" high and dried fruit size small, the larger chain size should be used. As harvest progresses and sugars increase, the hazard of removing "good" fruit increases and the smaller chain size (or no sizing depending on the orchard) should be considered.
4. Monitoring: It is important to continually monitor what is being removed when field sizing. Periodically sample the fruit being thrown out, dry it and determine amount of undersize and good fruit being eliminated. Without monitoring, valuable fruit loss may occur.

Watch Out for Brown Rot

Brown rot is being observed in the field. Rovralr, applied within 5 weeks of harvest (as fruit touch and begin to ripen), has been shown to provide protection from brown rot. Note, an additional treatment may be necessary if wet weather occurs following 7-14 days of the treatment.

Recommended Ground Squirrel Control Program

The control of ground squirrels in California is important in two ways. First, it is necessary to prevent destruction of agricultural crops and facilities. Second, it is important from a health standpoint where rodent-borne diseases have been demonstrated to be present.

Ground squirrels have enormous "come-back" powers. As long as an adequate food supply is available, their annual litters will average about six to eight young. Therefore, a few years of neglect by the growers may create new centers of population which will reinfest clean areas. There are several essential steps to consider before control is undertaken:

1. The selection of a toxic grain bait if prebaiting indicates that the squirrels are taking grain.
   
2. If grain isn't readily taken, which fumigant will do the best job.
   
3. If grain or fumigation cannot be used, should trapping or shooting be implemented.

The chart below shows ground squirrel activities throughout the year in Fresno County. These activity periods vary from year-to-year, as much as three or four weeks. Due to climatic conditions (rain and temperature), the breeding may vary. Fluctuations in material application may occur 10 to 15 days in either direction of the below periods. The months of December through January are usually poor periods for control efforts due to the hibernation period. February through April are fumigation months. Anticoagulant bait stations also work well in some instances during this period. May through July are grain months. Large areas should be treated during this period to keep control costs at a minimum. August and September are the estivation months. During this period, the activity slows down following a few hot days and may continue two or more months, depending on the area. In some areas, a brief time during October or November, effective control measures may be applied with excellent results. The ultimate results of any rodent control program are entirely dependent on the effort expended by the person in charge of the job. It is essential that all phases of field work be carefully observed so that any changes in rodent activity, bait acceptance, and degree of kill will be noted. The comprehension of these factors will result in a high degree of efficiency and ultimately a more effective and economical control program.

From time to time during the year, it may be necessary to call the Agricultural Commissioner to evaluate your ongoing program or to get advice on current ground squirrel control in your area. Call (209) 733-6391 if you have any questions or concerns.

TABLE 1
DRIED PRUNE SIZE

*To convert dried count per pound at 18% moisture to other moisture content multiply table value by (100-%H20)/82.