Eggplant - Thrips

Thrips

General

Rather polyphagous globally distributed insects, present from the tropics to the polar regions depending on the species. They feed by sucking the contents of cells in the epidermis, so damaged tissue quickly necrosis.
Classified in the order of Thysanoptera, and the family of Thripidae .
* Species reported on vegetables: Thrips tabaci , Frankliniella occidentalis, Thrips , palmi Heliothrips haemorrhoidalis, etc.
Some are vectors of formidable viruses, in particular the Tomato spotted wilt virus (TSWV, etc.).
Observed in the open field and under shelters.

* The first two species are very polyphagous, developing on several hundred hosts, cultivated or not, while the others are present in a few botanical families.

Organs attacked: leaves, fruits, stems and petioles.
Symptoms :
- Numerous and tiny silvery lesions, even patches of irregular size and shape appear on the limbus (figure); they gradually necrotize and take on a beige tint.
- Presence of tiny black dots materializing thrips droppings.
- Affected leaves and leaflets tend to chlorinate and take on a dull color.
- Whitish lesions on the flowers (figure).
- Silver, even suberized, more or less extensive alterations developing on the fruits (figure).

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Signs : Presence of tiny insects lying on the affected plant organs (figures).
Possible confusion :

Biology

Development cycle : comprising 6 stages: egg, two larval stages, two pronymph stages and adult; its duration varying according to the temperature and the host plant (for example, for F. occidentalis it fluctuates from 34 days at 15 ° C to 13 days at 30 ° C).
- Kidney-shaped eggs deposited on aerial organs, especially leaves.
- Larvae, once formed, very mobile and feeding on the underside of the leaves. At the end of the second instar larvae, they drop to the ground and pupate.
- The first pronymph stage is characterized by the appearance of wing outlines. The second, clearer, pronymphal stage also shows more substantial wing outlines and long antennae curved towards the rear of the body.
- Adults with 2 pairs of well-developed wings.
Larvae and adults, taking refuge in places with mild temperatures, ensure the sustainability of these insects. For this, they settle in the plant debris, the frames of the shelters; they sometimes bury themselves up to 8 centimeters deep. They can also hibernate on field crops, especially on various Alliums .
Insects fairly easily spread passively entrained by drafts and / or actively flying. Workers can contribute to their dispersal during cropping operations; this is also the case for plants or plants of other parasitized species.
The nature of the plant, the temperature, the humidity in the crop, notably influence the development of thrips.

Protection

Create a crawl space on the farm if the thrips populations are important.
Leach with water and treat the walls of shelters, posts, concrete walkways.
Disinfect the reused substrate or soil.
Produce the seedlings in an nursery insect-proof .
Check the sanitary quality of the plants before and during their introduction into the crop or shelter.
Install canvases insect-proof at shelter openings when weather conditions allow.
When growing under cover, detect the first pests using blue sticky panels placed above the crop as soon as the plants are introduced.
Remove and destroy infested plant debris and crop residues.
Favor natural enemies in field crops or under open shelters.
Introduce auxiliaries into closed shelters if available.
Reason the chemical protection ** (e-phy), in particular if you use auxiliaries.
Treat plants before uprooting in the presence of high populations of pests so as not to contaminate nearby sensitive crops.