International Workshop on Bemisia spp.
An International Workshop on Bemisia spp. was held in Israel, in 1994-10-03/07. Many papers and posters have been presented on the following topics: basic biology of whiteflies, population dynamics, damage expression of Bemisia tabaci and other whiteflies, viruses, plant resistance to whitefly-transmitted viruses or to whiteflies; international cooperation in research and control, biological control of Bemisia and Trialeurodes, chemical and physical control of whiteflies and their resistance to insecticides, control of Bemisia in IPM systems. From the abstracts the EPPO Secretariat has noted the following items.
1) Insect surface lipids have been be used to differentiate closely related species and geographically separated populations of Diptera, Hymenoptera and Orthoptera. Nelson and Buckner compared the composition of surface lipids of Trialeurodes vaporariorum, Bemisia tabaci, Bemisia argentifolii, Aleurothrixus floccosus, Aleuroplatus coronata and Parabemisia myricae. Whitefly species appear to be very similar in the composition of their wax particles and their major cuticular surface lipids, though some differences could be noted. B. tabaci and B. argentifolii could not be differentiated based on the components of their exterior lipids.
2) Frohlich and Brown have used the mitochondrial 16S ribosomal subunit of Bemisia tabaci as a molecular marker to assess variability among individuals (collected from different places on four continents). These studies indicated that B. tabaci is composed of at least three distinct groups: one composed of New World B. tabaci, a second composed of Old World B. tabaci (excluding the Indian subcontinent) and the B biotype (B. argentifolii), and a third group composed of B. tabaci from India and Sudan. They concluded that, based on mitochondrial 16S rDNA analyses, the present taxon B. tabaci is more complex than previously demonstrated.
3) Guershon and Gerling have analysed the effect of cotton leaf pubescence on the phenotype of Bemisia tabaci pupae. The percentage of setaceous pupae per leaf increased with leaf pubescence. These setaceous whiteflies developed to maturity more rapidly than the smooth individuals present on the same leaves. They have also observed, by transferring B. tabaci crawlers from pubescent to glabrous leaves and vice versa, that the setaceous phenotype is induced before the whitefly nymphs settle and feed from the leaf fluids.
4) Dr Xu Rumei presented the situation of Bemisia tabaci on cotton in China. Previously, it was not considered as a serious cotton pest in China and was only reported in the extreme south (Taiwan, Yunnan, Hainan). However, recently it was found to be distributed on a much larger scale, up north to the Yantze river drainage area (Shanghi, Wuhan etc.).
5) Cohen et al. reported that in 1992 unusual symptoms appeared on lisianthus (Eustoma grandiflorum) plants in Israel. The symptoms included distortion of growing tips, cup-shaped leaves and swelling of the veins on the lower leaf surface. This disease has become a limiting factor to the production of lisianthus in Israel. The authors have found that this disease was induced by tomato yellow leaf curl geminivirus.
Sources
Abstracts of papers presented at the International Workshop on Bemisia spp. (1994)
Phytoparasitica, 22 (4), 309-361.