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Honeysuckle (Lonicera)

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.