3-ha field site selected to evaluate the salt 3.0 dS/m. The levels for the 4 subirrigation times during the season to raise the water tolerance of corn on Delta organic soil. It is treatments are the same except that the 3.0 table to within about 0.1 m of the soil sur- located on the Marian Fry farm on Ter- dS/m treatment is omitted. Water for the face. minous Tract, San Joaquin County. The least saline treatment is taken directly from Land preparation, planting, fertilization, soil, about 2 meters deep, is typical of the the south fork of the Mokelumne River. and cultivation are performed by the farmer Delta soils in composition and uniformity. During the growing season, the river water and they match those for corn grown in the The experimental design, shown schemati- has an average electrical conductivity of area. One of the typical corn varieties, cally in figure 2, consists of 5 sprinkler-ir- about 0.2 dS/m and a chloride concentra- DeKalb XL 75, is being grown. Yields will rigated treatments replicated 6 times and 4 tion of nearly 10 mg/l. The remaining water be determined by hand harvesting the subirrigation treatments replicated 4 times. treatments are prepared by mixing the river center portion of each plot. In addition to The sprinkler treatments are irrigated with water with saline well water. The well, drill- grain yield, plant density, plant height, and low-level sprinklers to provide uniform ed near the experiment, delivers water hav- stover weight will be determined and cor- water applications with ample leaching. The ing an EC of 8.1 dS/m and a chloride con- related with soil salinity measurements. resultant soil salinity profiles should centration of 2200 mg/l. This three-year study, supported in part simulate those in standard salt tolerance by the California State Water Resources Irrigation treatments trials so that the results can be compared Control Board and the California Depart- with those from trials of other crops. The The sprinklered plots are irrigated weekly ment of Water Resources, is in its initial subirrigation treatments are similar to the to meet the evapotranspirational demand of year. It will be finished, however, before commonly accepted irrigation practices for the crop plus about 50 percent additional the water quality standards in the Delta are corn in the Delta. Comparison of the two water for leaching. This maintains fairly reevaluated in 1982. systems provides the means to evaluate any uniform soil salinity throughout the root differences in salt tolerance because of the zone. Leaching is possible in the sprinkler G.J. Hojjtnun and E. V. Muas are with the U.S. Salinit! Laborutory, USDA/SEA-AR, Riverside. Jewel1 L. irrigation method. plots because we installed subsurface drains Meyer and Terry L. Prichard are Soil and Wutiv The salinity levels of the water used in the on a 15-m spacing at a depth of 2 m. The Specialists, U.C. Cooperative Extension. Donald R. Lancaster is Staff Research Assistant, U.C. Co- 5 sprinkler treatments are 0.2, 0.6,1.0, 2.0, subirrigation treatments are irrigated 3 operati ve Extension. Caprif icat ion: A unique relationship between plant and insect Marvin Gerdts 0 Jack Kelly Clark

By transferring pollen from inedible caprifgs to edible Smyrna-types, a tiny wasp helps create an important com mercial crop.

InCalifornia, the fig, like many other Smyrna-type figs to obtain fruit-set (a that can be transmitted by Blastophaga. fruits, was introduced when the mission at process called “caprification”). This suc- Gustav Eisen described the fig wasp life San Diego was established in 1769. Com- cess stimulated interest in commercial pro- cycle and its relationship to caprifigs in mercial culture started in 1885 and dried duction of Calimyrna (Sari Lop, California 1901. Ira Condit, U.C. Subtropical Horti- Adriatic figs were shipped east in 1889; but Smyrna) figs in California, and acreage ex- culturist, added further descriptions in these were inferior in eating quality to im- panded in the early 1900s. 1918 and 1920. Their descriptions of ported Smyrna-type figs. Smyrna figs, Pollination of Calimyrna figs involves caprification, a horticultural word used to which require pollination to set fruit, were complex symbiotic relationships between describe the pollination process in figs, il- introduced into California in 1881-1882, caprifigs and the fig wasp. Over the years, luminated the complex relationships of but it was not until about 1900-through University of California researchers have plant and insect. the efforts of George Roeding of Fresno investigated and described these relation- Caprification and L. 0. Howard and Walter Swingle of ships. They have also studied methods of the USDA-that the fig wasp, Blastophaga using fig wasps in the commercial produc- The fig fruit is a hollow peduncle bearing psenes L., was established and used suc- tion of Calimyrna figs, while insuring that numerous pistillate (female) flowers on the cessfully to transfer caprifig pollen to the crop is protected from fruit diseases inner wall. For Calimyrna fruits to mature,

12 CALIFORNIA AGRICULTURE. NOVEMBER-DECEMBER 1979 Fertilized female wasp emerges from a gall flower in the caprifig (17.6~life-size).

these flowers must be pollinated from an viable seeds. Eggs are not laid in female suited to fig-wasp egg laying. In the ovaries external source, and nature has provided flowers of Calimyrna figs because the of these flowers, the larvae hatch and de- the very specialized fig wasp to transfer flower structure is not suited to oviposition velop. Adult male wasps emerge from the pollen from the male caprifig to Calimyrna by the wasp. gall flowers first and fertilize the females fruits. Without caprification, Calimyrna The fig wasp relies on caprifigs to repro- before they leave the galls. After mating, figs grow to Yi to ?4 inch in diameter and duce and complete its life cycle. It com- adult female wasps migrate in search of thc then turn yellow, shrivel, and drop before pletes three life cycles per year, coinciding succeeding caprifig crop and the cycle con- maturing. with the three caprifig crops: profichi tinues. The caprification process occurs from (spring) crop; mammoni (summer) crop; the end of May into June. Adult female and mamme (winter) crop. Female adults Further studies wasps emerge from caprifigs and enter emerge from maturing caprifigs seeking U.C. Plant Pathologist P. D. Cddis de- Calimyrna figs, seeking egg-laying sites. In egg-laying sites in the succeeding overlap- scribed an internal fig rot problem in 1925 the process, pollen carried on the wasp ping crop. They proceed by seeking Capri- and 1927. He suggested the name endosep- bodies is spread to female flowers and re- figs, which they enter to deposit eggs on sis for the fungus disease caused by Fusari- sults in fertilization and the production of modified female flowers (gall flowers) um moniliforme (Sheld.) Snyder and Han-

CALIFORNIA AGRICULTURE, NOVEMBER.DECEMBER 1979 13 Caprifigs are placed in slotted paper bags in Calimyrna orchards. Female wasps that emerge from these figs will enter the edible Calimyrna figs in search of suitable egg- lavina sites.

Female wasp emerges from the eye of a caprifig. She will then fly to another fig to lay her eggs (15x life-size).

Female wasD enters the eve of acalimvrna fia (17x life-size).

sen. Caldis found the fungus in caprifigs sured crop-set while minimizing disease and showed that it was transmitted to Cali- and fruit-split. myrna figs by the fig wasp. By 1950, Robert Warner (California Fig Treatment to control endosepsis was de- Institute and U.C.) described refinements veloped by H. N. Hansen, another U.C. of Hansen’s endosepsis clean-up program. Plant Pathologist. In a series of investiga- As mercuric fungicides had to be replaced, tions beginning in 1926 he developed a other fungicides were tested and recom- caprifig dipping technique which is still mended by U.C. Food Technologist M. W. used by the fig industry. Miller and Gerdts and Obenauf of U.C. From 1944 through 1946 Simmons and Cooperative Extension in the late 1960s Fisher (USDA), Condit and Hansen and early 1970s. Fungicide studies were (U.C.), and Tyler (California Fig Institute) again resumed in 1977 by Obenauf and researched caprification procedures. They U.C. Plant Pathologist J. M. Ogawa as ad- determined the number of wasp-egg laden ditional disease problems were encoun- caprifigs needed per Calimyrna tree, the tered. best distribution pattern of caprifigs within U.C. researchers continue the search for a Calimyrna orchard, the frequency of ways to best utilize the fig wasp to enable caprifig distribution, and the number of California growers to produce abundant, Female wasps try to lay their eggs in female times caprifigs should be distributed during high-quality figs. flowers inside the Calimyrna fig but fail be- the caprification season. The studies result- cause the styles are too long. While strug- Marvin Gerdts was formerly Extenyion PomoloRist, gling to lay their eggs, the wasps transfer ed in standardization of caprification U. C., San Joaquin Valley Agricultural Research and Extension Center, Parlier; andJack Kelly Clark i\ Senior pollen to the flowers, thus ensuring fruit-set schedules and provided guidelines that in- Photographer, Cooperative Extension, U. C., Davis. (14x life-size).

14 CALIFORNIA AGRICULTURE, NOVEMBER-DECEMBER 1979