Polyphagotarsonemus latus  (Banks)

Tarsoneme - deforming acariosis

General

• Tiny mite (0.2 mm) white or yellowish and translucent (Figures 1 and 2), with an oval body. 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 chili peppers are sensitive, but also eggplant and sometimes tomato), but it is also found on fruit trees , ornamentals and weeds.
• Localized mainly at the level of the apex and buds, and on the underside of the leaves.
• Global distribution.
• Observed in the open field as well as under shelters.
• Organs attacked : leaves, flowers, fruits.
• Symptoms :
  • Strong deformations of young leaves and buds resulting from its bites (figures 3 and 4 - chili) (figures 8 and 9 - tomato). These symptoms are reminiscent of those caused by hormone-type herbicides, or by certain viral diseases.
  • Rolling up of the leaves which are also folded, thicker and rigid (figures 5 - chilli) (figure 10 - tomato). They sometimes show a bronze to brownish tint, 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 - chilli) (figures 11 to 13 - eggplant).
  • Growth of some plants stopped, but may start again if the mites are eliminated.
  • Browning, or tanned appearance of inflorescences which may drop off.
• >>>  More pictures
• Signs : mites not observable with the naked eye on the affected organs (figures).
• Possible confusion : virus diseases, herbicide damage, etc.

Biology

• Conservation : Able to survive 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 egg-to-adult cycle lasts 5 days in warmer periods, and longer in cooler temperatures.
  • Eggs located in particular on the underside of young leaves, or even young fruits, oval and slightly flattened. They give birth to larvae.
  • Larvae not very mobile, of very small size, hyaline and having 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.
• Dispersion : by movement over short distances, males being more mobile than females. Disseminated in cultivation by wind, animals and insects (especially whiteflies), workers and their tools during cultivation operations.
• Favorable conditions : temperatures around 25 ° C, no rain.

Protection

• Control rather difficult because this mite is often detected too late in crops by the first damage it causes.
• Weed the crop and its surroundings.
• Disinfect greenhouses and equipment used.
• Check the sanitary quality of the plants before and during their introduction into the crop or shelter.
• Produce the plants in a clean shelter. However, nurseries insect-proof are insufficient to prevent the entry of mites due to their very small size and their mode of dissemination.
• Reason for  chemical protection, in particular if you use auxiliaries or biopesticides ***.
• Attempt to eradicate the first outbreak (s) by eliminating the first affected plants and / or locally treating them and surrounding plants.
• Use a large volume of mixture and with sufficient pressure to access 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 Phytoseidae mites have been tested in Europe to control populations P. latus . Certain natural substances of plant and mineral origin have also been tested against P. latus , in particular fine clay in suspension.