Honeysuckle (Lonicera)
Plant Health Problems
Diseases caused by Fungi:
Leaf blight, Herpobasidium.
Leaves are deformed, thickened, and curled, often with whitish bloom. This
disease is favored by wet weather and is usually not considered a serious
problem.
Pruning and destroying infected branches is helpful as is raking and removing
all fallen leaves and fruit. Control can also be achieved with the use of
fungicide sprays applied when new growth emerges in the spring. Several
applications may be necessary, especially when wet weather persists. Among the
compounds registered for use in Connecticut are mancozeb and copper. Consult
the label for dosage rates and safety precautions.
Powdery mildew, Microsphaera.
White powdery spots or patches develop on the leaves, usually during mid-
to late summer. Leaves are usually not obviously curled or deformed and although
some defoliation can occur, this disease is not considered a serious problem.
Disease can be minimized by carefully picking off affected leaves as soon as
symptoms are evident and by raking and removing fallen leaves to reduce the
amount of overwintering inoculum. This disease is generally not serious enough
to warrant chemical control although fungicide sprays can be applied as soon as
symptoms are visible. Among the compounds registered for use in Connecticut are
myclobutanil, thiophanate-methyl, and sulfur. Consult the label for dosage rates and
safety precautions.
Diseases caused by Bacteria:
Crown gall, Agrobacterium tumefaciens.
Distinct swellings develop on the stem at or slightly above the ground
level. These can be found on one or more sides and appear as round galls with a
rough or irregular surface. The bacteria causing these galls enter the plants
through wounds and stimulate an abnormal proliferation of plants cells to make
the gall. Honeysuckle and euonymus are particularly susceptible to infection.
Roguing and removing infected plants helps to prevent spread of the bacterium
to nearby healthy plants. Any tools should be disinfested with 10% bleach or
70% alcohol between cuts. It is also important to avoid wounding plants during
cultivation since wounds are necessary for infection.
Insect Problems:
Aphids, Rhopalosiphum conii and Hydaphis tartaricae.
At least three species of aphids attack honeysuckle. Two, Rhopalosiphum
conii and Hydaphis tartaricae, feed on the leaves, and the other is
a woolly aphid, Prociphilus xylostei, which attacks both leaves and
twigs. Feeding by Hydaphis causes witches' brooms on branch tips of bush
honeysuckle that are killed by frost. If necessary, sprays of ultrafine
horticultural oil, insecticidal soap or malathion, which are among the
compounds registered for use against this pest in Connecticut, will control
these aphids. Imidacloprid, applied as a systemic to be taken up by the roots,
will also provide season-long control. Consult the label for dosage rates and
safety precautions.
European honeysuckle leafroller, Ypsolophus dentella.
The larva of this insect is a leaf roller of the Tartarian honeysuckle, and
sometimes causes a very ragged appearance of the leaves. It is leaf-green with
two chocolate median stripes and a lighter blue-green stripe on each side of
the median stripes. It reaches a length of nearly 3/4", thickest at the
fifth abdominal segment, from which it tapers to a narrow head and tail. The
cocoon is white, fastened to a leaf and has sharp points at both ends. The moth
is chestnut-brown, with cream-colored rear margin on forewings. Tips of
forewings are extended backward and form recurved hooks. Wing spread is about
4/5".
Ultrafine horticultural oil, spinosad or acephate, which are among the compounds registered for use against this pest in Connecticut, sprayed on the foliage as soon as the caterpillars are noticed should provide control. Consult the labels for dosage rates and safety precautions.
Honeysuckle sawflies, Zaraea inflata and Z. americana.
Climbing and bush honeysuckles are sometimes stripped of leaves by the larvae
of these sawflies. Fully grown larvae are 1" long, dull gray with
yellowish stripes on the top and sides. There is a row of black spots along the
back in the middle of a yellowish stripe. There is one generation each year.
The insects winter as pupae in the ground and the adults emerge in April. They
are medium-sized sawflies that resemble small bees. Both have brown-clouded
forewings; Z. americana has a metallic green abdomen, and Z. inflata
a black abdomen with a yellow ring at its base and silver pubescence on the
rear margin of each segment. Malathion or spinosad, which is among the
compounds registered for control of this pest in Connecticut, sprayed when
larvae are seen feeding will protect the foliage. Consult the labels for dosage
rates and safety precautions.
Snowberry clearwing, Hemaris diffinis.
The larvae of this moth feed on Tartarian honeysuckle and are called hornworms
because each has a horn on the tail like other sphinx moth caterpillars. There
are two generations each season and the insects overwinter as pupae in the
ground. The moths emerge in May and lay eggs on the food plant; the
caterpillars feed until the middle of June, when they pupate. The moths soon
emerge and lay eggs for the second generation of larvae. The caterpillars vary
from dark green with lighter green on the back to brown or purplish, with
spiracles very prominent. The moths have a wing spread of from 1 1/2 to
2". All wings are transparent with dark brown margins. The body is black
marked with golden pubescence. If needed, spray with Bacillus thuringiensis
var. kurstaki when the caterpillars are young, or malathion or spinosad
late in May or early in June to control the first generation. Both products are
registered for use against this pest in Connecticut. A second treatment in July
may be required for the second generation. Consult the labels for dosage rates
and safety precautions.