ACQUISITION AND TRANSMISSION OF PSEUDOMONAS-CICHORII BY LIRIOMYZA-TRIFOLII (DIPTERA, AGROMYZIDAE)

Adults of the serpentine leafminer, Liriomyza trifolii (Burgess) were able to acquire and transmit Pseudomonas cichorii (Swingle) Stapp. both in vitro from cultures of the bacteria, and in situ from infected to non-infected chrysanthemums. Forty-three percent of adult leafminers exposed to P. cichorii in culture jars acquired the bacterium. More infected leafminers were detected by homogenizing (43.0%) as compared to rising (15.0%), suggesting ingestion of bacteria by leafminers. The use of the wetting agents Tween 20(R) and bacitracin enhanced the recovery of P. cichorii from homogenized adults of L. trifolii. A mean of 7.9 bacterial leafspots per plant was observed after a 48 h exposure of healthy chrysanthemums to 10 adult leafminers which had been confined on infected chrysanthemums for 24 h. Less than 5% of leafminers observed under a scanning electron microscope had detectable bacterial particles on the cuticle that were in the size range expected for P. cichorii. Larval leafminers acquired P. cichorii and transmitted bacteria as did adults when confined to culture jars. When P. cichorii was introduced to chrysanthemums after oviposition by leafminers, there was a 41.7% reduction in subsequent emergence of prepupae.