Bemisia tabaci

10.01.2025 | 10:33 (UTC -3)

Bemisia tabaci It is popularly known as whitefly, being one of the main agricultural pests in Brazil and in the world.

Taxonomic classification:

Domain: Eukaryota (organisms with eukaryotic cells; contain cell nucleus and membranous organelles)

Kingdom: Animalia (heterotrophic multicellular organisms that feed by ingestion)

Phylum: Arthropoda (characterized by animals with segmented bodies, chitinous exoskeletons, and jointed appendages)

Class: Insecta (insects, group characterized by three pairs of legs, body divided into head, thorax and abdomen, and generally presence of wings)

Order: Hemiptera (insects that have mouthparts adapted to suck plant sap)

Suborder: Sternorrhyncha (specialized phytophagous insects such as scale insects, aphids, and whiteflies)

Family: Aleyrodidae (specific family of whiteflies, characterized by small white or yellowish insects that infest plants)

Genre: Bemisia (genus that includes several species of whiteflies specialized on plant hosts)

Species: Bemisia tabaci

In Brazil, at least four different biotypes are recognized: B, Q, BR and N.

Biotype B: the most common and widely distributed in Brazil. It is considered an efficient vector of several plant viruses.

Biotype Q: also known as MEAM1 (“Middle East-Asia Minor 1”). This is an invasive biotype originating from the Mediterranean region. Scientists consider it a more efficient vector of viruses compared to biotype B.

BR Biotype: native to Brazil. It has been reported mainly in regions with tropical and subtropical climates. It is less efficient in transmitting viruses compared to biotype B.

Biotype N: still little studied in Brazil. It was identified in some regions of the country from 2015 onwards.

Crops attacked

Whiteflies have a wide range of host plants. The most affected crops of economic interest include: soybeans, cotton, beans, tomatoes, peppers, potatoes, cabbage, melons, pumpkins and grapes.

Additionally, several weeds can also host the pest, maintaining their presence during the off-season.

Biology

The whitefly undergoes incomplete metamorphosis. It goes through a development cycle that includes three main stages: egg, nymph (juvenile) and adult, without a true pupal stage as occurs in complete metamorphosis.

Eggs: These are small, elongated and usually laid on the underside of leaves. They are initially light in color, but darken as the embryo develops.

Nymphs: emerge and remain attached to the plant, continuously feeding on phloem sap. Nymphs go through four instars, with the first instar being mobile (called a "crawler"), while the others are sessile.

Pupa: in the last instar, the nymphs enter the pupal phase, characterized by morphological changes that prepare the insect for the adult phase.

Adult: These are small winged insects, approximately 1 mm long, white or yellowish in color. Their wings are covered in a layer of wax, which gives them their characteristic white appearance.

Reproduction can be sexual or parthenogenetic, being influenced by factors such as temperature and food availability.

A female can lay 100 to 300 eggs during her lifetime. The complete cycle varies from 20 to 26 days, depending on the host plant.

Ecology

The insect is highly adaptable and agile, and can fly long distances aided by the wind.

It feeds by sucking the sap from plants, causing direct and indirect damage.

Populations can remain high during the off-season in weeds, increasing pressure on the following season.

Damage

Damage caused by whiteflies includes:

Sap sucking: Adults and nymphs suck the sap from plants, weakening them and reducing growth and productivity. This can lead to wilting and premature leaf fall.

Toxins: during feeding, the whitefly injects toxins that cause physiological disorders in the plant, such as leaf deformations and reduced photosynthetic capacity.

Excretion of honeydew: the release of sugary substances (honeydew) creates a sticky layer on the leaves, which serves as a substrate for the growth of fungi such as sooty mold. This reduces photosynthesis and compromises the quality and productivity of the plants.

Virus transmission: whiteflies are vectors of geminiviruses and other viruses that cause diseases that can lead to a drastic reduction in productivity.

Increased pressure from other pests: the presence of whiteflies and the damage they cause can encourage the development of other pests and diseases in the crop.

Control

Whitefly management requires an integrated approach:

Cultural control: use of healthy seedlings and elimination of host plants and crop residues.

Chemical control: judicious use of insecticides, respecting the safety interval and avoiding consecutive applications of the same active ingredient, as recommended by IRAC.

Biological control: Although limited in Brazil, the use of entomopathogenic fungi as an alternative to chemical control has shown promising potential.