Gladiolus thrips are a tiny, oblong insect with feather-like wings. It's thought thrips are closely related to the true bugs (Hemiptera) because their mouthparts are strikingly similar, with many feeding on plant sap. There are many thrips that specialise primarily on fungi and pollen, but it's the sap-feeding thrips that are the most damaging pests in gardens, allotments and agriculture. Gladiolus thrips specifically target the flowers, corms and foliage of Gladiolus plants.
Serious thrips infestations may cause malformed flowers and silvery-white scars in Gladiolus.
Adults are only 2mm and brownish-black in colour. Bodies are elongate, possessing two pairs of wings with fine filament hairs that are prominent towards the wing-tips. Nymphs are tiny, thin and pale yellow. They take a similar form to adults but lack wings — the next moult results in a slightly larger nymph, which are a darker yellow. The next development stage is known as the pre-pupal stage. At this point, thrips do not feed on plant matter. They burrow within the soil media to pupate and mature to the adult form.
Thrips tend to target plant foliage, flowers and corms. Foliage will start to fade and develop a silvery finish. Small red dots speckled over leaves may be evident, which is thrips excrement. These insects may distort new shoots and flowers. Some flowers turn brown, and some may not open. Corms may be infested with small brown insects when pulled up. Rough grey patches may be evident on the infested corm.
Attracting predatory insects such as lacewing can help control thrips in your garden. However, such biocontrol is not recommended for commercial growers that may use chemicals to eradicate pests. When storing corms, dispose of any growth above soil before the corm has fully dried. This may help reduce the number of overwintering thrips.
Organic insecticides are suggested if you have noticed significant infestations. There are more persistent chemicals available, however, these must be researched and instructions followed carefully before application. Pesticides should never be applied to flowering plants because they can harm beneficial insects.