The British Gladiolus Society
Pests and Diseases Part II
Gladiolus Rust Uromyces transversalisThümen
The Gladiolus rust
, Uromyces transversalis is a disease of quarantine importance in Europe and the United States. Because it attacks mainly hybrid cultivars it would have serious consequences if it became established in greenhouses or nurseries.
The sori or spore producing bodies are unusual as they develop across the width of the leaf rather than longitudinally along the veins as in most monocots.
Botrytis
This disease is usually associated with the later part of the season when days are still warm but nights are cool and there is a large amount of moisture in the atmosphere. It is usually compounded by a lack of air flow around the leaves of the plant, especially evident if planted too closely together. The symptoms are small brownish spots on the leaves which often merge to form larger areas which eventually may develop into a mouldy grey growth.
Virus
There are many virus diseases which may occur resulting in mottled, streaked or spotted leaves.
The effects on the florets can be patches of colour that are different from the norm ie white or purplish.
In some cases, corms may also be affected becoming shrivelled. Some viruses cause curling of poor small spikes, small corms and poor root development. Important to destroy such plants
Thrips Taeniothrips simplex
The thrip is potentially the worst pest to attack gladiolus - it can also attack other garden plants. It has the ability to severely damage a whole crop. The symptoms are not usually noticed until the infestation has occurred and by this time it is
usually too late to rescue the situation. The one saving grace is that the insect cannot overwinter out of doors in northern Europe and northern North America.
Plants severely infested with gladiolus thrips have a spotted, bleached appearance with silvery streaking between the leaf margins. Both leaves and petals act as a food source and will appear withered. If flower buds are seriously damaged,
the flowers fail to open. The entire plant may become stunted.
The eggs are opaque, white, kidney-shaped, and about 0.34 mm long and 0.2 mm in diameter. Gladiolus thrips emerge as creamy yellow larvae, but soon turn dark brown, except for the tips of the legs which are lighter.
The wings are brown above and lighter below and appear to be darker with a grey band when folded over the back. Gladiolus thrips are about 1.5 mm long and extremely slim. Males are smaller and lighter in colour than the females.
The life cycle of the thrip is very much determined by the weather and in warmer conditions several generations can be produced in a short time hence the apparent sudden epidemic.
Slugs And Snails
Both slugs and snails can cause damage but in most cases it is purely cosmetic, however a severe attack to the leaves can affect the plants ability to produce a new corm for the next season. Slugs have the potential to destroy the growing shoot of a newly planted corm but once established the plant should be safe from their clutches. Snails can affect the florets and make them unsuitable for exhibition.
