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Gladiolus | America’s Favorite Garden Beauty Has Its Share of Problems

Gladiolus | America’s Favorite Garden Beauty Has Its Share of Problems

Gladiolus (genus Gladiolus) also known as Sword Lily, is one of America’s most revered summertime plants. It produces tall, stately flowers which reach heights of 2 to 4 feet. The blooms have colors ranging from white, red and orange to pink, lavender and yellow, and even mixed colors. This gorgeous perennial, which originates from South Africa and the Mediterranean regions of Europe, is born from bulbs (corms) and is a member of the iris family, Iridaceae.

The most common diseases and pests associated with gladiolus are:

Botrytis Blight (Botrytis gladiolorum), also known as gray mold, produces small brown/reddish spots on either side of the plant’s leaves which turn soft and rot. It can also affect the flowers of gladiolus, which can cause them to turn brown and fall off. The corn can also be infected at top of the corms (soil line) and will show tiny black particles.

Curvularia Leaf Spot (Curvularia trifolli f. sp. Gladioli) typically show up as large circular brown spots surrounded by a yellowish hue. The disease is produced by infected corms, so be sure to make sure the corms have been pretreated to protect them against Curvularia Leaf Spot before purchasing them.

Fusarium Yellows (Fusarium oxysporum f. sp. Gladioli) manifests as infected corms that show circular, sunken brown spots on the surface and will quickly spread outward. If roots are produced from the corm, they will eventually turn brown and rot. If the flower produces stalks and flowers, they will be irregular and will quickly perish. If you notice any sign of infection on the corms, don’t plant them.

Gladiolus Rust (Uromyces transversalis) is an invasive fungus believed to have originated in South Africa that began infecting fruit and ornamental trees and soybeans crops. The rust has since begun damaging gladiolus by causing foliar infections, which stress the plant. The fungus produces yellow spots on either side of the leaves and develops into large orange abscess-like lesions that can overtake large portions of the leaves. The disease is dispersed by spores carried by the wind or through direct contact with other plants.

Gladiolus Scab (Pseudomonas syringae) shows us as infected corms with round, sunken brownish lesions that can quickly spread to the corm necks causing soft rotting. Do not plant corms if they show any signs of infection and disinfect any tools or hard surface the corm may have come in contact with to prevent spreading of the disease.

Root-Knot Nematodes (Meloidogyne spp.). An infestation of these microscopic roundworms can severely damage the root system by producing smaller roots or developing galls on the root nodes. The plants can become underdeveloped and may produce flowers late. It is a good idea to plant the corms in soil that has been pasteurized or sterilized and to carefully remove any weeds that may appear near the plant.

Stemphylium Leaf Spot (Stemphylium botryosum). This disease is most prevalent on larger, more mature leaves of gladiolus. Infected leaves will show round, small yellow spots surrounded by a reddish hue.

Stromatinia Dry Rot (Stromatinia gladioli). This fungus usually begins on the leaves, which ultimately yellow and eventually die. The leaves can also produce tiny black fungal spots on the dead areas. Wet leaves and soil conditions can make the symptoms of this disease worse. If infected at the soil level, plants can develop neck rot, which typically occurs on younger corms during summer months and will quickly kill young plants.

Before purchasing gladiolus corms, check with the seller to find out if the corms were washed with hot water and pretreated with fungicides. Look over every inch of the corm to double-check for any signs of disease. Discard any infected corms and destroy infected plants. Plant new corms in pasteurized and/or sterilized soil and add a light application of fungicide. Maintain a soil pH of 6.6-7.0 and use a nitrate-based fertilizer if needed. Water the plants at ground level and try to avoid working with wet plants. Maintain weed and pest control regularly to ensure healthy viable plants and luscious blooms.

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