Grape
Black Vine Thrips
Retithrips syriacus
Insect
In a Nutshell
- Silvery patches on leaves and fruits.
- Grey and shiny black dots on leaves (insect excrement).
Can also be found in
Grape
Symptoms
The thrips suck sap from the host leaves, causing defoliation and shriveling. Silver patches appear due to the insertion of stylets on the leaf. At feeding sites, the fruit turns grey. When infestation is heavy the fruit becomes unsightly and fails to develop normally.
Recommendations
Organic Control
Introduce natural enemies such as Geocoris ochropterus and Metaseiulus occidentalis (predators). Predatory thrips, green lacewings, minute pirate bugs, and several phytoseiid mites help control plant-feeding thrips.
Chemical Control
Always consider an integrated approach with preventive measures together with biological treatments, if available. Thrips can be difficult to control effectively with insecticides, partly because of their mobility, feeding behavior, and protected egg and pupal stages (life stages in the development of insects exhibiting complete metamorphosis that occurs between the larval and adult stages). Spinosad-based products are considered organic control tools. Always, follow regional regulation on pest management.
What caused it?
Damage is caused by both the adult and larvae (young thrips) which feed on the plant sap. Thrips hatch from an egg and develop through two actively feeding larval stages. The adult female measures about 1.4 to 1.5 mm long and the male are 1.3 mm. It is a dark to blackish brown species. The hatched larvae start feeding almost immediately, usually in groups. Newly emerged adults are lighter and reddish. The thrips feed on the lower leaf surface but when the infestation is heavy, the upper surface is also attacked especially during cooler months. In warmer conditions, the life cycle from egg to adult may be completed in as short as 2 weeks.
Preventive Measures
- Avoid planting susceptible plants.
- Practice regular and periodic monitoring of the thrip population and control nearby weeds that are alternate hosts of pest thrips.
- Grow plants that are well-adapted to conditions at that site.
- Provide appropriate cultural care to keep plants vigorous and increase their tolerance to thrips damage.
- Keep plants well irrigated, and avoid excessive applications of nitrogen fertilizer, which may promote higher populations of thrips.
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