Tobacco whitefly
| Tobacco whitefly (Bemisia tabaci (Gennadius) |
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| Adults (x30) | 'Pupa' (x30) |
QIC/6
HOSTS: A wide range of protected ornamental and vegetable crops.
DISTRIBUTION: Widespread in Africa, Asia, Australasia and Central
America. Also present in several South American countries and in the southern
parts of North America. Occurs in many European countries, but is typically
of limited distribution in northern Europe as a glasshouse pest.
SOURCES: Imported plants, especially Poinsettia and Begonia
cuttings.
DESCRIPTION AND LIFE CYCLE: Eggs are pear shaped, 0.2 mm long,
and tend to be laid randomly on the underside of leaves, either singly
or in groups. (cf. The glasshouse whitefly (Trialeurodes vaporariorum)
which lays its eggs in a half circle). Hatching occurs after about 10
days at 25°C.
There are four immobile immature stages (nymphs), all of which appear
more yellow and more pointed at the rear end than those of the glasshouse
whitefly. The fourth nymphal stage, called a 'pupa', is 0.7 mm long and
has two red eyespots at the front end. It is not raised above the leaf
surface on a waxy base like those of the glasshouse whitefly and therefore
appears flatter.
Adults are whitish-yellow and about 1 mm long. They differ from adults
of the glasshouse whitefly in that the wings are held tent-like above
the body and slightly apart, so that the yellow tinged body is more apparent.
Adults can be detected by shaking plants, causing them to fly. Flight
is more direct than the haphazard flight pattern of the glasshouse whitefly.
Adults often vary in appearance, depending on the host species; laboratory
identification is therefore important.
The whole life cycle takes about 30 days at 25°C. Development is
halted at temperatures below 10°C and therefore in the UK, the tobacco
whitefly is only likely to be a pest of protected crops.
DAMAGE: The greatest potential threat from the tobacco whitefly
is that it can transmit more than 60 plant viruses including tomato yellow
leaf curl, lettuce infectious yellows and squash leaf curl. Direct damage
by feeding adults and nymphs is unlikely to be seen unless infestation
is severe. Detection of the pest therefore relies mainly on seeing adults
or immature stages. However, if infestation is severe, damage can occur
in the form of sticky honeydew and associated sooty moulds, chlorotic
spots and leaf yellowing. Physiological disorders such as leaf silvering
of cucurbits and fruit distortion of tomatoes may also be induced.
PEST STATUS: The tobacco whitefly is a serious pest that is listed
in EC plant health legislation because of its potential to introduce and
spread many non-indigenous viruses. If this pest is suspected, inform
your local Plant Health Inspector.
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Page last modified:
10 Oct 2006
Page published: 3 May 2003