Agriculture Reference
In-Depth Information
the glume. Eggs hatch about a week later and the
larvae feed for up to 2 months. Fully grown indi-
viduals are 2.0-2.5 mm long, reddish-orange
and distinctly oval-bodied; the anterior
protuberances of the very broad sternal spatula
are distinctly pointed (ear-like) (cf.
Contarinia
geniculati,
p. 170, and
C. merceri,
p. 170). Larvae
(in common with those of
C. geniculati)
remain
within the dead florets, even after these have
dropped to the ground. Pupation occurs in the
spring. This pest is spread readily within infested
seed, the latter failing to be removed by normal
post-harvest cleaning processes.
edges often turning purplish-red. The leaf folds
often afford protection to young larvae of
summer fruit tortrix moth,
Adoxophyes orana
(p. 212). Damage is of particular significance on
young trees but attacks on mature trees rarely
prove of significance. Larvae (up to 3 mm long)
vary from translucent-white or creamish-white to
red or orange. They feed gregariously and are
fully grown in about 2 weeks; most then pupate
in the soil. There are usually three generations
annually but up to five in parts of continental
Europe.
Dasineura pyri
(Bouche)
Pear leaf midge
Dasineura leguminicola
(Lintner)
Clover seed midge
This pest occurs on pear, especially on young
trees, where the larvae cause a distinctive longi-
tudinal curling of the young leaves. The larvae,
which are whitish and up to 2 mm long, feed
gregariously on the upper epidermis, within the
shelter of the tightly rolled leaf margins. Infested
leaves are discoloured; they frequently turn red
and, finally, black. There are usually three gen-
erations annually, and the pest tends to become
more numerous later in the season. In dry
summers, the number of generations may be
restricted to two.
This widely distributed and generally common,
reddish to orange-coloured midge is associated
with red clover. The larvae are capable of caus-
ing significant damage to seed crops; affected
plants flower irregularly, buds fail to open prop-
erly and the heads turn brown prematurely.
Affected seeds are often distorted and may be
invaded by secondary fungal pathogens. Eggs
are deposited singly, or in small batches, in the
furled heads of clover plants, usually in June.
They hatch a few days later. The neonate larvae
immediately migrate into the floral parts, and
down the corolla tube, to feed adjacent to the
ovary. The pinkish larvae, each with a distinct,
sharply cleft sternal spatula are fully fed in 4-6
weeks. They then vacate the flowers and drop to
the ground to spin silken pupal cocoons within
the soil. A second generation of adults emerges
2-3 weeks later. There are usually up to three
generations annually; larvae of the final genera-
tion pupate in the following spring, shortly
before the appearance of the adults.
Dasineura tetensi
(Riibsaamen)
Black currant leaf midge
This midge is often a persistent pest of black
currant. The larvae feed in the shelter of the
young leaves. The infested leaves fail to develop
properly and become crumpled and discoloured,
affected tissue often turning black. Attacks are
particularly significant on young bushes and
cuttings. Adults are active from April onwards.
Eggs are then deposited in small batches in the
folds of the unfurling leaves, usually at the shoot
tips. The translucent to whitish larvae feed gre-
gariously for about 2 weeks and then drop to
the ground to pupate in cocoons in the soil.
New adults appear about 2 weeks later. There
are normally three overlapping generations an-
nually but sometimes a partial fourth.
Dasineura mali
(Kieffer)
Apple leaf midge
Infestations of this widely distributed midge oc-
cur on apple, eggs being deposited in the margins
of young apple leaves. Infested leaves are tightly
rolled longitudinally and distorted, the rolled
