Polyphagotarsonemus lateralis (Banks)

Tarsonema - acariosis deformans

General

• Tiny mite (0.2 mm) white or yellowish and translucent (figures 1 and 2), whose body is oval in shape. Almost invisible to the naked eye despite its rapid movement.
• Very polyphagous, reported in many plant species belonging to more than 60 botanical families, including most vegetable crops (peppers and peppers are susceptible, but also eggplant and sometimes tomato), but it is also found on fruit trees , ornamental plants and weeds.
• Localized especially at the level of the apex and the buds, and on the underside of the leaves.
• Worldwide distribution.
• Observed in the open field as well as under shelter.

Susceptible botanical family(s)

Production areas affected :

Organs attacked

Symptoms, damage

Symptoms :

Strong deformations of the young leaves and buds consecutive to its bites (figures 3 and 4 - pepper) (figures 8 and 9 - tomato). These symptoms are reminiscent of those caused by herbicides , or by certain viruses.

Rolling of the leaves which are also pleated, thicker and more rigid (figures 5 - pepper) (figure 10 - tomato). They sometimes have a bronze to brownish hue, and their underside has shiny reflections.

Areas of brownish or corky tissue appear under the leaves, on the petioles or sepals, but especially on the fruits (figures 6 and 7 - pepper) (figures 11 to 13 - eggplant).

Growth of some plants stopped, but may resume if mites are eliminated.

Browning, or bronze appearance of inflorescences which may drop.

Signs : mites not observable with the naked eye on the affected organs (figures ).

Possible confusion : viruses, herbicide damage, etc.

Biology

Conservation : Capable of being maintained all year round on different hosts, whether cultivated or not, in tropical or subtropical zones.

Development cycle : Three stages follow one another during its biological cycle: egg, larva and adult. The duration of the cycle from egg to adult is 5 days in warm periods, and it is longer if the temperatures are cooler.

Eggs located in particular on the underside of young leaves, even young fruits, oval and slightly flattened. They give birth to larvae.

Little mobile, very small, hyaline larvae with 3 pairs of legs. These feed for 2 to 3 days.

Adults have 4 pairs of legs but the fourth is not functional. Males are smaller than females. They have a lifespan of about 2 weeks and lay an average of 2 eggs per day.

Dispersal : by movement over short distances, males being more mobile than females. Disseminated in the crop by the wind, animals and insects (especially whiteflies), workers and their tools during cultivation operations.

Favorable conditions : temperatures around 25°C, no rain.

Protection

Rather difficult to control because this mite is often detected too late in crops by the first damage it causes.

Weed the crop and its surroundings.

Disinfect the greenhouses and the equipment used.

Control the sanitary quality of the plants before and during their introduction into the culture or shelter.

Produce the seedlings in a clean shelter. nurseries insect-proof are insufficient to prevent the entry of mites given their very small size and their mode of dissemination.

Consider  chemical protection ( e-phy )**, in particular if you use auxiliaries or biopesticides ***.

Attempt to eradicate the first outbreak(s) by eliminating the first affected plants and/or treating them locally and the surrounding plants.

Use a large volume of mixture and with enough pressure to reach the "heart" of the vegetation. The effectiveness of the treatments should be monitored over time.

Treat plants before uprooting in the presence of high pest populations.

Remove and destroy plant debris and crop residues

*** Predators such as certain phytoseid mites have been experimented in Europe to control populations of P. latus. Certain natural substances of plant and mineral origin have also been tested against P. latus , in particular fine clay in suspension.