Whitefly Infestation
This information sheet concerns not a domestic animal but a crop pest insect: the whitefly. The species Bemisia tabaci and Trialeurodes vaporariorum are tiny piercing-sucking insects that attack vegetable and ornamental crops, both in green...
What is it?
This information sheet concerns not a domestic animal but a crop pest insect: the whitefly. The species Bemisia tabaci and Trialeurodes vaporariorum are tiny piercing-sucking insects that attack vegetable and ornamental crops, both in greenhouses and in the field. They weaken plants by feeding on their sap and transmit numerous plant viruses. It is a major agricultural problem, particularly in Tunisia where protected crops (tomato, courgette, melon) are especially at risk.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
On infested plants, yellowing of the leaves is observed, along with progressive wilting and slowed growth. Leaves often become covered with a sticky film, honeydew, secreted by whiteflies, on which a black mold called sooty mold subsequently develops. When the foliage is shaken, a cloud of tiny white insects can be seen flying away. Young stages (larvae) remain fixed under the leaves, visible as tiny whitish or translucent dots. Fruits may show irregular ripening or spots linked to viruses transmitted by the insects.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Infestation results from the proliferation of adult whiteflies and their larvae, which feed on plant sap using their piercing-sucking mouthparts. These insects reproduce very rapidly, especially in warm and humid conditions such as those found in greenhouses. A single female can lay a large number of eggs on the underside of leaves, giving rise to several generations within weeks.
The warm and confined conditions of greenhouses strongly favor whitefly development. The presence of susceptible host plants (tomato, eggplant, courgette, melon, cotton, ornamental plants) increases the risk. Introduction of seedlings or cuttings already infested, absence of crop rotation, high plant density, and excessive use of insecticides that destroy natural enemies (predators and parasitoids) are also aggravating factors.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis is made by direct observation of the foliage, particularly on the underside of leaves where larvae settle. Yellow sticky traps placed in the crop help confirm the presence of adults and assess the extent of infestation. An agricultural technician or a crop protection advisor can help identify the precise species of whitefly involved, which guides the choice of the most appropriate control methods.
Treatment
Control combines several approaches: biological control using predatory or parasitoid beneficial insects, judicious use of specific insecticides applied in rotation to prevent resistance, and physical methods such as sticky traps or protective netting. Removal of heavily infested plants or crop residues after harvest also reduces reinfestation sources.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention is based on several combined measures. Regular inspection of plants before planting prevents introduction of already present insects. Installation of insect netting at greenhouse openings limits whitefly entry. Yellow sticky traps allow early detection of infestation and monitoring of its progression. Promoting natural enemies of whiteflies, such as certain parasitoid wasps or predatory bugs, helps naturally regulate populations. Good management of irrigation and plant density also limits spread.
Possible complications
Beyond the direct weakening of the plant, the main complications are transmission of serious plant viruses (such as yellowing or stunting viruses), formation of sooty mold that reduces photosynthesis, and significant yield losses that can completely compromise a crop in the case of severe uncontrolled infestation.
When to see a veterinarian
A cloud of small white insects takes flight at the slightest contact with the foliage.
Yellowing, sticky leaves or leaves covered with a blackish deposit.
Notable slowing of growth or wilting of several neighboring plants.
Appearance of viral symptoms on the fruit (spots, deformations, abnormal ripening).
Prognosis
The outlook for the crop depends on how early the infestation is detected and control measures are implemented. An infestation caught early remains manageable with limited impact on yield. Conversely, an advanced infestation, especially if viruses have already been transmitted, can result in significant crop losses that are difficult to recover from.
Frequently asked questions
Do whiteflies bite humans or domestic animals?
No, whiteflies are pests that exclusively affect plants. They do not bite humans or animals and pose no health risk to them.
How to quickly identify an infestation?
Simply shake the foliage lightly: if a cloud of tiny white insects flies away, you are very likely dealing with whiteflies. Examining the underside of the leaves will confirm the presence of the larvae.
Are yellow sticky traps sufficient to eliminate whiteflies?
No, yellow sticky traps are mainly used to detect and monitor infestation. They capture some adults but are not sufficient on their own to eradicate an already established population.
Why are whiteflies a serious problem in Tunisian greenhouses?
The hot, confined conditions of Tunisian greenhouses, used for tomatoes and zucchini in particular, are ideal for the rapid reproduction of whiteflies, making their control especially important for preserving harvests.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
Content reviewed by the TunisieVet editorial team · Updated 26 August 2026
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