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Pests of gladiolus | AG0185 |
David Williams, Knoxfield
June, 2000 |  |
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Gladiolus thrips Taeniothrips simplex
Thrips are minute insects that feed by rasping plant tissues and sucking the sap. Gladiolus thrips cause serious damage to late flowering plants and to stored gladiolus corms. The leaves of infested plants develop a bleached and silvered appearance, the flower spikes are stunted, flowers may not open, or are distorted and the petals are marked with small pale flecks. Damage to dark-coloured varieties is most noticeable and even a few flecks are enough to considerably reduce the value of the flower.
Young nymphs feed inside the leaf tubes and buds. If the plants are left in the field for a long time after flowering, the thrips enter the corms and continue feeding. Stored corms are attacked by thrips, which cause a sticky exudate. The infested corms later become hard and scabby. When the damaged corms are planted out, the thrips begin feeding on the young roots, and growth from the corm may be seriously affected.
Bulb mite Rhizoglyphus echinopus
This slow moving mite is about 0.5 mm long, globular, and yellow-white with brownish legs. Infested corms produce stunted plants with yellow and distorted leaves. Early infestations are found around the basal plate of the old corm. Roots are destroyed first and stems are attacked later. Corms can be completely destroyed by the combined action of the mites and micro-organisms that invade the damaged tissue.
Hot water treatment will kill the mites, but good sanitation is very important when digging up, storing, or planting out corms.
Budworms Heliothis spp.
Budworms are the larvae of noctuid moths. The species that attack gladiolus 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.
Painted apple moth Teia anartoides
When the caterpillars first hatch from the eggs they are nearly black, but as they mature they become brownish. When fully grown, they are about 45 mm long, with a thick covering of long hairs and have two red 'pimples' projecting from the back near the tail. The head is dull reddish-brown, lightly covered with long greyish hairs, with a tuft projecting from either side just behind the head. The thoracic segments are marked with yellow and the first four abdominal segments have a brush-like bunch of greyish hairs in the centre of the back.
The fully grown larvae spin a flimsy light-brown silken cocoon through which the pupa can be seen. Female pupae are about twice the size of the male pupae. The male moth has a wingspan of about 25 mm. The forewings are dark-brown with yellow and grey markings with a dark transverse band. The hindwings are orange-yellow in the centre, with a broad black band encircling them and fringed on the outer edge with yellow.
The female moth is wingless, thickly covered with short brown hairs and has rudimentary antennae and legs. After emergence from the pupal case, the female remains near the cocoon. After mating, the glossy white almost-spherical eggs are laid on and around the cocoon. Each female can lay about 700 eggs.
The larvae attack a wide variety of plants including Acacia, Melaleuca, Callistemon, Grevillea, fruit trees, roses, pelargoniums and berry bushes. They may eat the whole leaf or skeletonise it. They are active throughout the year but may be more obvious during winter because the larval stage takes longer to complete in winter.
Aphids
Several species of aphids attack gladiolus. All infest the foliage and also transmit virus diseases. Aphids are slow moving and plump bodied insects. The colour varies with the species and green yellow, pink, brown and black forms occur.
Chemicals registered for control of pests on gladiolus
Current registrations for pesticides against any of these pests can be checked at district offices of DPI. The chemicals may not be registered specifically for gladiolus but may be registered under the broader category of ornamentals. It is the grower’s responsibility to check that any chemicals used are 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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