Squash silverleaf symptoms induced by Bemisia tabaci immatures
Studies were carried out in Hawaii (US) to investigate the involvement of Bemisia tabaci (EPPO A2 quarantine pest) immatures in the induction of silverleaf symptoms on squash (Cucurbita pepo). Plants infested with 20 adult whiteflies for 48 h with a subsequent removal of immature offspring of the pest did not develop the typical silverleaf symptoms. In contrast, if the immature stages were allowed to stay and feed on the plants the plants developed silverleaf symptoms. A significant regression was found indicating a positive relationship between the severity of silverleaf and the number of immature B. tabaci present on a plant. Furthermore, it was discovered that adult whiteflies were not able to induce the disease even at very high infestation levels. Plants infested with 20 adults per day for each of 10 consecutive days did not develop any silverleaf symptoms.
Sources
Costa, H.S.; Ullman, D.E.; Johnson, M.W.; Tabashnik, B.E. (1993) Squash silverleaf symptoms induced by immature, but not adult, Bemisia tabaci.
Phytopathology 83, 763-766.