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Pests of carnations | AG0181 |
David Williams, Knoxfield
June, 2000 |  |
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Aphids
Aphids are small plump-bodied insects that feed by sucking sap. Several species of aphids attack carnations but the most common is green peach aphid Myzus persicae. They secrete copious amounts of honeydew, which favours growth of sooty moulds, and they reduce plant vigour by sucking sap. Their most important effect is the transmission of viruses while feeding.
Two spotted mite - Tetranychus urticae
The adult female is about 0.5 mm long. The adult male is about 0.3 mm long. In the summer feeding stage the adult females are a yellowish-green, with two pronounced dark spots, one on either side of the body. In males these spots are less conspicuous and the body is smaller and tapered towards the rear. Both sexes possess two reddish eye-spots.
Under artificial long day length or in warm situations such as glasshouses, the mites may continue feeding and reproducing through the winter. Outdoors, when temperatures and day length decrease in autumn, the males die and the adult females stop feeding and change colour to orange-red. They usually migrate to sheltered sites where they congregate to overwinter. When the temperatures increase in spring, the females leave their shelters and begin to feed, losing their red colour in the process. They lay up to six eggs a day and usually lay a total of 70 or more. Males develop from unfertilised eggs and females develop from fertilised eggs.
Egg hatch takes from three to 10 days depending on the temperature. The young mites mature in from four to 12 days and may live for about three weeks. In hot weather the complete life cycle may be as short as two weeks and overlapping generations may occur. Damage occurs when nymphs and adults feed by piercing the cells of leaves and sucking the contents, causing collapse and death of the cells. The mite is a profuse web-spinner in its active stages and eggs are laid amongst the webbing.
Heavily infested leaves become pallid and may become bronzed and shrivelled. Defoliation may occur.
Plague thrips - Thrips imaginis
Adult female plague thrips are narrow-bodied, light-brown or grey and 1-2 mm long. Males are smaller and yellow. Both sexes have two pairs of narrow delicate wings fringed with long hairs. The wings lie along the back when not in use. The colourless eggs are inserted into the tissue of petals, sepals, blossom stems, stamens, pistils, calyx cups and young leaves.
The nymphs feed on the stamens, pistils and petals. When full grown they crawl to the ground and pupate about 50 mm under the surface. Generation times vary from 10 days to more than a month, depending on the temperature.
Thrips have mouthparts adapted for rasping and sucking. Unlike bugs they do not have tubular mouthparts and are therefore unable to penetrate deeply into plant tissue. Feeding by thrips is usually confined to soft recent growth or flowers where they rasp the surface cells and suck the sap as it oozes out. Petals and anthers turn brown and shrivel. Normal opening of flowers may be affected if thrips enter before the flowers open. Feeding and egglaying on the pistil may cause it to wither.
Egglaying in the tender tissue of young leaves may cause the tissue around the eggs to die and fall out leaving small, irregularly shaped 'shot-holes'.
In addition to damage done by feeding, crops may also be downgraded by faecal deposits.
Carnation shoot-mite - Eriophyes (=Aceria) paradianthi
This eriophyid mite was found infesting carnations in Australia in the mid to late 1980s. Eriophyid mites are wormlike and range in length from 0.1 to 0.3 mm, which makes them too small to be easily seen by the naked eye. They also have considerable reduction in body structure; the two pairs of hind legs and most body setae have been lost and the front legs are reduced.
The mites live between the leaf bases and stems and are numerous on the lower portions of the plants. They have been discovered in Victoria on several properties and there they were also numerous under the sepals. The plants lose colour and may become distorted and stunted, with a greasy appearance.
Budworms - Heliothis species
Budworms are the larvae of noctuid moths. The species attacking carnations in Victoria are the same ones that attack tomatoes and sweetcorn. They feed mainly on the young shoots and foliage, flower buds and heads. They make characteristic round holes in buds and flower heads. The caterpillars are about 40 mm long when fully grown, have various shades of yellow, green, pink or brown, with dark flecking and longitudinal paler and darker stripes.
Chemicals registered for control of pests on carnations
Current registrations in Victoria against pests on carnations can be checked at local offices of DPI. The chemicals may not be registered specifically for carnations but may be registered under the broader category of ornamentals. Care should be taken to avoid the use of pesticides which may be phytotoxic to the crop plants. Those registered for a specific host plant should be safe to use on that plant but chemicals registered under the broad category of “general ornamental use” may be phytotoxic to some plants.
It is the grower's responsibility to check that the product being used is registered for the purpose .
For effective pest and disease control, correct diagnosis is essential. A commercial diagnostic service is available at the Institute for Horticultural Development. For further information, contact the Diagnostic Service. ph: (03) 9210-9222 or fax (03) 9800 3521.
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
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