VIEW ARTICLE

Vector Relations

Dynamics of Blastophaga psenes Populations, Availability of Caprifigs, and Fig Endosepsis Caused by Fusarium moniliforme. T. J. Michailides, Associate plant pathologist, Department of Plant Pathology, University of California, Davis, Kearney Agricultural Center, 9240 S. Riverbend Ave., Parlier 93648; D. P. Morgan, staff research associate, Department of Plant Pathology, University of California, Davis, Kearney Agricultural Center, 9240 S. Riverbend Ave., Parlier 93648. Phytopathology 84:1254-1263. Accepted for publication 17 August 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-1254.

Propagules of Fusarium moniliforme, which causes endosepsis of Calimyrna figs, were vectored on the body of the fig wasp pollinators, Blastophaga psenes. Scanning electron microscopy indicated that microconidia and mycelial fragments of F. moniliforme were attached to the wasps’ bodies along with grains of pollen. Contamination of adult fig wasps occurred after they emerged from the flower galls, the specialized flowers within a fig syconium in which the wasp eggs hatch and develop. No adult wasps artificially removed from the flower galls were infested with propagules of F. moniliforme but 91–100% of those that emerged from infected syconia of pollinator cultivars (caprifigs) became contaminated. On bagged branches, more than twice as many spring crop caprifigs were infested with F. moniliforme after pollination with five or 10 winter crop caprifigs than when only a single winter crop caprifig was used. Similarly, more than twice as many wasps emerging from spring crop caprifigs that had been pollinated with five or 10 winter crop caprifigs were infested with F. moniliforme than were wasps from spring crop caprifigs pollinated with only one winter crop caprifig. Furthermore, pollination of Calimyrna figs with spring crop caprifigs that had been pollinated with five or 10 winter crop caprifigs resulted in higher incidence of endosepsis than when only one winter crop caprifig was used. The use of more spring crop caprifigs than necessary for pollination of Calimyrna fig increased the number of wasps entering the cavities of Calimyrna syconia. The relationship between the number of wasps in the syconium cavity and incidence of endosepsis in the cavity or ostiole of Calimyrna syconia was described with a second degree polynomial equation (R² = 0.94 – 0.98; P < 0.01). The presence of three or more wasps in the fruit cavity resulted in 100% incidence of F. moniliforme on the ostioles while the presence of five or more wasps resulted in 100% incidence of contamination within the cavity. In the field, incidence of fig endosepsis increased when high populations of wasps coincided with limited availability of receptive fruit crop.