Grape thrips

The grape thrips (Drepanothrips reuteri) is a small insect belonging to the order Thysanoptera and the family Thripidae, recognized as a primary pest in viticulture.

Adults are approximately 1 mm long with a yellowish-brown body, featuring two pairs of slender wings fringed with hairs, which are characteristic of this order.

The immature stages, known as larvae, are pale, wingless, and highly mobile, allowing them to rapidly infest the young growth of the vine.

Their life cycle is highly dependent on temperature, completing development from egg to adult in as little as two weeks during warm summer conditions.

Overwintering typically occurs as adults in the bark crevices of the vine or in leaf litter and topsoil, emerging when temperatures rise in early spring.

This pest feeds by rasping the surface tissues of leaves, shoots, and inflorescences, sucking out the cell sap and destroying the plant cells.

The injury causes significant physiological stress to the vine, often leading to reduced photosynthesis and impaired nutrient transport throughout the plant.

Severe infestations during the flowering stage can lead to bud drop and significantly lower the final yield of the vineyard.

Young shoots may become stunted, twisted, and brittle, which hinders the development of the structural framework of the vine.

The damaged tissue is highly susceptible to secondary pathogens, including various types of fungi that exploit the necrotic areas caused by the thrips.

Activity commences in the spring, typically correlating with bud break and the initial emergence of green tissues as temperatures reach 10–12°C.

The period of peak population density and maximum damage usually occurs between May and June, coinciding with the rapid growth of primary shoots.

While activity might plateau during extremely hot and dry summer months, localized colonies continue to persist on the undersides of leaves.

As the season progresses toward autumn, the insects look for protected overwintering sites, often near the base of the vine or in soil debris.

Proactive monitoring throughout the early growth season is essential to identify the start of an infestation before it reaches critical levels.

The most visible signs of infestation include curling, crinkling, and bronzing of the young leaves near the shoot tips.

Small, dark, necrotic spots often appear on the undersides of leaves, which are diagnostic indicators of the thrips' feeding activity.

Inflorescences may shrivel, turn brown, and drop prematurely, resulting in poor fruit set and cluster development.

Stunted growth of new shoots, resulting in a bushy or distorted appearance, is a common symptom in severely affected vineyard blocks.

• Distorted and curled leaves.
• Bronze discoloration of leaf surfaces.
• Premature shriveling of flower clusters.
• Stunted terminal shoot growth.
• Presence of tiny dark fecal specks on foliage.

Effective management begins with strict orchard sanitation, including the removal of weeds and debris where the pest finds shelter during winter.

Biological control, utilizing predatory mites (e.g., Amblyseius spp.) or natural predators like lacewings, can help maintain population levels below economic thresholds.

Yellow sticky traps should be deployed in the vineyard for monitoring purposes, providing data on the timing of peak emergence for better treatment planning.

When chemical intervention is required, systemic insecticides should be applied carefully, targeting the areas where the insects congregate on the foliage.

Integrated Pest Management (IPM) practices, such as rotating insecticide modes of action, are crucial to prevent the development of resistance in thrips populations.