INTRAPLANT AND INTERPLANT MOVEMENT OF BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) CRAWLERS

Whitefly crawlers are thought to move only a few millimeters after ecl osing from the eff before settling to feed. In the field, however, we observed that crawlers of Bemisia argentifolii Bellows & Perring appea red 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 m ovement). B. argentifolii crawlers readily moved along the stem of 4 t est plants and settled on leaves greater than or equal to 50 mm from t heir initial point of origin on the stems. Crawlers traveled an averag e 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 sowt histle, Sonchus oleraceus L.; prickly lettuce, Lactuca serriola L.; an d cheeseweed, Malva parvifolia L., respectively, to find a suitable le af on which to settle. The maximum distance traveled by a single indiv idual from the point of origin to settling on a leaf was 204 mm on ann ual sowthistle. Eighty to 100% of the crawlers successfully reaching a leaf settled on the abaxial surface; the remainder settled on the ada xial surface. Between 7 and 12% of the crawlers successfully moved bet ween the test plants, migrating from a senescent leaf of 1 plant (sour ce leaf) to a healthy leaf (destination leaf) of a 2nd plant. Crawler movement may be important in whitefly overwintering because emerging c rawlers can move from senescent leaves, which would not support develo pment to the adult stage, to healthy leaves on either the same or adja cent plants where they can complete their development.