Agriculture Reference
In-Depth Information
infestations debilitate host plants and sometimes
cause premature leaf loss. The mealybugs also
contaminate plants with honeydew, upon which
sooty moulds develop.
BIOLOGY
Mealybugs breed continuously whilst conditions
remain favourable, and there is a succession of
overlapping generations throughout the year.
Eggs are deposited in batches, often in the axils
of leaves, each batch surrounded by cottonwool-
like masses of wax that form a loose ovisac. Fol-
lowing egg hatch, the nymphs wander over host
plants but they will often accumulate within
curled leaves or beneath leaf sheaths. The adults
are also mobile.
Fig. 198
Root mealybug,
Rhizoecus falcifer
(x40):
(a) antenna (further enlarged).
Rhizoecus falcifer
Kiinckel de Herculais
Root mealybug
DESCRIPTION
Adult
4mm long, pinkish, coated with whitish
wax;
caudal filaments
about half as long as
body.
Egg
minute, oval, pinkish.
Nymph
similar in appearance to adult but smaller.
Colonies of root mealybugs often occur on the
roots of glasshouse plants; infestations are most
often found on ornamentals. The foliage of at-
tacked plants becomes dull. Also, heavily in-
fested plants eventually wilt. The insects shelter
in masses of whitish wax and breed par-
thenogenetically, there being a succession of
generations throughout the year. Adults are
elongate, 1.0-2.3 mm long, and greenish-yellow
but coated liberally in whitish wax. They are
readily distinguished from root aphids by their
stubby, 5-segmented, geniculate antennae
(Fig. 198);
they also have very short waxy anal
appendages.
Pseudococcus longispinus
(Targioni-Tozzetti)
Long-tailed mealybug
The long-tailed mealybug is often common in
glasshouses. It is distinguished from the previous
species by its smaller size (body
c.
2.5 mm long)
and by the distinctive caudal filaments, which are
noticeably longer than the body.
ORDER COLEOPTERA (BEETLES)
Family CARABIDAE
(ground beetles)
Harpalus rufipes
(Degeer)
Strawberry seed beetle
seeds from ripening strawberries but cleanly and
from the more exposed parts of fruits.
BIOLOGY
Larvae usually overwinter in the grassy sur-
roundings of fields. They emerge in the spring to
feed on invertebrates and seeds of various plants,
especially
Chenopodium album
and
Lolium;
unlike the adults, however, they do not attack
strawberry fruits. Larvae usually complete their
development by July and then pupate. Young
Infestations of this generally common carabid
often occur in strawberry fields during the fruit-
ing period. The adult beetles remove seeds from
the ripening fruits and, particularly if seeds are
deeply set, will also injure the surrounding flesh.
Linnets
{Carduelis cannabina
(L.)) also remove
