Bemisia tabaci ,  Trialeurodes vaporariorum , etc

Whiteflies or white flies

General

• Rather polyphagous insects widely distributed in the world, and particularly damaging in tropical areas. Certain species are vectors of numerous and formidable viruses. They belong to the order Hemiptera and the family Aleyrodidae.
• The adults resemble almost entirely white midges, about 1 to 3 mm long depending on the species, and are mostly found on young leaves. The larvae, flattened, have an oval shape and are whitish or dark in color, covered or not with white waxy secretions depending on the species, which allows them to be recognized. However, the color of the larvae can change if they are parasitized by micro hymenoptera. These larvae can be confused with mealybugs, but these are rare on vegetable crops and we will not observe "white flies" in this case.
• These insects are observed in the open field and in crops under cover.
• Examples of some species of halibut affecting Solanaceae and therefore eggplant: Bemisia tabaci , B. argentifolia, Trialeurodes vaporariorum , Aleurotrachelus trachoides , Aleurodicus dispersus, etc.
• Organs attacked : leaves, fruits.
• Symptoms :
  • Numerous bites and sap sucks causing a slowdown in plant development and sometimes leaf chlorosis.
  • Honeydew produced in large quantities by these insects. This substrate is subsequently colonized by opportunistic fungi responsible for sooty mold (figures). The mold produced covers the surface of the aerial organs of plants, soiling them, sometimes making the fruit unsuitable for marketing, and decreases photosynthesis.
  • Many viruses such as TYLCV (figure) and PYMV can be transmitted by eventually Bemisia tabaci, in particular on Solanaceae, leading to the death of the plant. Trialeurodes vaporariorum can sometimes transmit viruses.

• >>> More pictures  
• Signs  : Presence of larvae and adults on the affected organs (figures). Sooty mold (figure) is often associated with the presence of whiteflies. Remember that the latter leads to a reduction in photosynthesis and leaf respiration and makes the productions non-marketable.
• Possible confusion :

Biology

• Development cycle : includes 3 development phases taking place on the underside of the leaves of attacked plants: egg, 4 larval stages and adult. Only the first larval stage is mobile and the last at the end of development is called the nymph or puparium. The duration of the complete cycle (figure) varies depending on the temperature, the host plant and the different species, and is approximately 3 weeks in tropical conditions. In tropical conditions, cycles are continuous and all stages are present at the same time.
• These insects persist on their cultivated plants as long as they persist, but also on various weeds, which should therefore be carefully eliminated.
• Dispersal : Adults are little fliers but are easily blown away and disperse quickly in crops. The dissemination of infested plants contributes to the dispersal of these insects.
• Favorable conditions  : whiteflies multiply rapidly in tropical climatic conditions, and more in shelters (absence of rain and wind, excess nitrogen fertilization).

Protection

• Create a crawl space on the farm if the whitefly populations are important.
• 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 sticky yellow panels placed above the crop as soon as the plants are introduced.
• Favor natural enemies in field crops or under open shelters.
• Introduce auxiliaries into closed shelters if available.
• Reason for  chemical protection, in particular if you use auxiliaries or biopesticides, especially since most insecticides are not very effective on whiteflies.
• Treat plants before uprooting in the presence of high pest populations so as not to contaminate nearby host crops.