Intraplant and interplant movement of Bemisia argentifolii (Homoptera: Aleyrodidae) crawlers

Whitefly crawlers are thought to move only a few millimeters after eclosing from the eff before settling to feed. In the field, however, we observed that crawlers of Bemisia argentifolii Bellows & Perring appeared to move from senescent leaves on which they hatched to new leaves higher up on the plant. Laboratory studies were conducted to determine if crawlers were capable of moving upward to leaves higher up on the plant (intraplant movement), or laterally between plants (interplant movement). B. argentifolii crawlers readily moved along the stem of 4 test plants and settled on leaves greater than or equal to 50 mm from their initial point of origin on the stems. Crawlers traveled an average distance of 73.5 +/- 2.0, 69.9 +/- 3.5, 64.3 +/- 2.2 and 55.0 +/- 0.9 film on broccoli, Brassica oleracea variety botrytis L.; annual sowthistle, Sonchus oleraceus L.; prickly lettuce, Lactuca serriola L.; and cheeseweed, Malva parvifolia L., respectively, to find a suitable leaf on which to settle. The maximum distance traveled by a single individual from the point of origin to settling on a leaf was 204 mm on annual sowthistle. Eighty to 100% of the crawlers successfully reaching a leaf settled on the abaxial surface; the remainder settled on the adaxial surface. Between 7 and 12% of the crawlers successfully moved between the test plants, migrating from a senescent leaf of 1 plant (source leaf) to a healthy leaf (destination leaf) of a 2nd plant. Crawler movement may be important in whitefly overwintering because emerging crawlers can move from senescent leaves, which would not support development to the adult stage, to healthy leaves on either the same or adjacent plants where they can complete their development.