Tobacco whitefly (Bemisia tabaci)
Tobacco or cotton whitefly is a semi—hard-winged insect from the Aleyrodidae family. More than 100 years ago, it was discovered by the Greeks on tobacco crops and has since received many names in different countries, due to the wide geography of its habitat. It is believed that the insect began its development with hot climatic regions — the tropics or subtropics. According to one version, these countries are China, India, Pakistan, Iran, or Afghanistan. It is a dangerous quarantine object — it carries many viral diseases of plants. Despite its original habitat, it quickly took root in Europe and became one of the dominant parasites. By nature, polyphagous and phytophagous. Whitefly is harmful for more than 600 plant species from more than 60 families. It is guaranteed to protect yourself from this pest only by placing your greenhouse in Antarctica, where this species has not been recorded.
Description
Imago Bemisia tabaci is a small moth 1-2 mm long, yellow in colour with white wings. In sexual dimorphism of individuals, in addition to primary signs, such as oviposition in females, it is also possible to introduce an indirect one, such as life expectancy. In females, it is up to two months, and in males no more than 3 weeks. At the same time, there are two females for one male. During the period of life, females lay from 100 to 300 eggs. Basically, they can be found on the back of the leaf. The eggs are oval, have an orange colour and a size of about 0.2 mm. Adult insects live on both sides of the leaf surface. The insect feeds on the juice of the plant. Due to the fact that tobacco whitefly requires amino acids for vital activity, it consumes a large amount of plant cell juices, and removes excess sugar from the body. These secretions are called pad or honeydew.
Stages of development
The tobacco whitefly has 6 stages of development — an egg, a mobile larval stage, 3 stationary larval stages, a stage of a false cocoon or puparia and an adult.
The egg is 0.2 mm in size, orange, and oval. It develops for 7-9 days, depending on the temperature, after which the larva of the first stage of development comes out of it.
The first stage of the larva of the tobacco whitefly is mobile and has the name “vagrant”. Within a few hours after its appearance, it actively moves along the back of the leaf in search of the optimal place to feed. After that, it settles there and goes into the next 3 stationary stages, actively consuming juices from the plant.
At the stage of puparia, the larva’s body is transformed, and the feeding process stops until it turns into an adult.
The damage caused
It is extremely dangerous in the closed ground. It carries about 100 phytoviruses. In addition to sucking out the juice of the plant, which leads to its weakening, and with mass distribution and death, it secretes a sticky honeydew. The honeydew attracts other insects to the plant, affects the external aesthetics, but what is much more terrible causes fungal diseases. All this weakens the ability to photosynthesis and the normal life processes of the plant.
How to detect?
The leaves of the plant lose colour due to the constant feeding of tobacco whitefly with its juices. A sticky plaque is formed in the form of honeydew, on which a black sooty fungus can be found. Larvae and eggs should be looked for on the underside of the leaf, a sufficiently bright colour facilitates the process to some extent. Adults have wings with a white waxy coating. Shaking the leaf, you can find a flock of small flying moths that quickly return to the plant.
Methods of struggle
The fight against tobacco whitefly is a complex process that requires a responsible approach. Preventive measures are needed, such as the destruction of affected plants, crop rotation control, soil steaming in the greenhouse. Because of the quarantine status, in case of detection of infected fruits and plants, all products will be returned or burned, in accordance with the law.
Whitefly is very resistant to insecticides. Therefore, it is necessary to regularly alternate them and use them in combination with other measures of influence.
Sticky and pheromone traps are used for monitoring and control. This method effectively allows you to control the pest population, destroy it and get information for analysis and taking measures to eradicate the problem.
Predatory bugs, parasitic wasps and predatory mites stand out favourably from biological means. Predatory bug, Macrolophus pygmaeus — feeds on various species of whiteflies, at all stages of their development. Predatory mite Amblyseius swirskii mainly feeds on whitefly eggs and larvae (one of the most dangerous stages of development), but also simultaneously monitors the population of thrips. Parasitic wasps, Encarsia formosa and Eretmocerus eremicus — parasitizes the larvae and puparia of whiteflies, thereby destroying them.