THE DISPERSAL AND ESTABLISHMENT OF PSEUDOMONAD POPULATIONS IN THE PHYLLOSPHERE OF SUGAR-BEET BY PHYTOPHAGOUS CATERPILLARS

The role of phytophagous insects in the dispersal of phyllosphere bact erial populations has been investigated. Following seed inoculation, a leaf colonising population of Pseudomonas fluorescens SBW25EeZY6KX (l acZY and aph-xylE) was established in field grown sugar beet (Beta vul garis var. amethyst). Third instar, Mamestra brassicae (Lepidoptera: N octuidae) larvae were placed onto the emerging leaves of mature plants and the dispersal of the marked strain (ca. 5 X 10(5) cfu/g leaf) to untreated plants monitored. Forty-two days after caterpillar introduct ion, approximately twenty days after pupation of the larvae, an establ ished population of transferred bacteria was detected at densities sim ilar to those determined for seed inoculated plants of the same age. U nder appropriate conditions phylloplane colonising pseudomonads can be dispersed by invertebrates and establish viable populations on the le aves of recipient plants.