Thrips

Thrips on Vinca

Thrips on leaf

Thrips damage - leaf

Thrips damage - Hibiscus

Thrips damage - Pepper

Thrips damage - Pepper

Thrips damage Citrus

Common name: Thrips

Order: Thysanoptera

Physical description

Thrips are small black or grey-winged or wingless insects under 2mm in size (normally 0.5 to 1mm). Insects are mobile and can normally walk or fly.

Gregarious, large populations build up very quickly in sheltered, warm, humid conditions. A single insect can multiply to several hundred within a few weeks. Activity is normally kept to the active growing portions (apical) of the plant or on the undersides of leaves.

Thrips prefer cool, dry portions of the plant that are actively growing. They are attracted in particular to light-colored flowers: white, yellow, and pale orange.

Description of damage

Thrips have rasping mouthparts that eat away at the epidermis of the plant. They normally attack the flowers or soft-growing tips and plant buds. The damage is cosmetic as the scars they leave on the tissue increase in size as the leaf or fruit does, leaving large visible blemishes or deformed floral parts. Normally once the damage is seen/ visible the insect is long gone.

This is a very common occurrence on citrus where long brown scars may appear on the skin as the fruit matures; generally, this damage was done weeks previously when the immature fruit was only a few millimeters in diameter.

Plants affected

A common problem on outdoor plants such as Vinca, Marigold, Peppers, Terminalia, Ixora, Citrus, Hibiscus, Codiaeum, Hemigraphis, Alternathera, etc.

Occasionally Thrips can be a pest on indoor plants, although not a major one.

General comments

Thrips are a common insect problem throughout the UAE both in the summer and winter months, although their damage is more apparent during the winter months when people spend more time outdoors.

Control methods - Natural

Simply removing (and discarding) damaged foliage can keep the problem at a manageable level. Damaged tissue does not repair, so the blemishes will remain even if the insect is killed.

Control methods - Cultural

The effects of Thrips can be minimized (not prevented), using cultural methods such as "catch crops" or "Companion planting". Sticky insect cards can also be placed between high-risk crops to catch as many flying adults as possible, thereby reducing the effects of the pest.

Control methods - Organic

Insecticidal oils such as Neem are also effective in controlling and breaking the breeding cycle, but only when used in a program with an emphasis on prevention not curing an existing problem.

Control methods - Chemical

Plants can be treated with a combination of systemic and contact insecticides. Care needs to be taken as most chemical treatments will have a residual period, so should not be used on edible crops.