Western Flower Thrips (Frankliniella occidentalis)
Western flower thrips, also known as California flower thrips, is currently the most damaging thrips species in many greenhouse crops and the most dangerous representative of the order of Thysanoptera. It was first discovered and described in California, for which it received one of its names. Thanks to active trade, he became a cosmopolitan and populated the entire globe with his population, except Antarctica. It is a polyphagous and feeds on more than 500 species of plants. It is ranked among a number of dangerous quarantine facilities and is strictly controlled when importing the product. If a thrips is detected, the party receives an import ban. In addition to direct damage to the plant, Western flower thrips carries various viruses, including the Tomato spotted wilt virus.
Description
Western flower thrips is a small insect, about 2 mm in size, with 2 pairs of fringed wings characteristic of thrips. It is for the fringe on the wings that this species has received another name — “fringe-winged” (Thysanoptera). The colour of the calf ranges from light yellow to dark yellow with a brown tinge. The oral apparatus is of a piercing-sucking type, thanks to which the insect easily pierces the epidermis of the plant to obtain food. There is a suction cup on the legs, which enhances the ability to manoeuvre when moving. The gender difference is characterized by the structure of the genitals and the lighter colour of the males.
Life cycle
The development of the Western flower thrips has 5 stages, which in turn have Egg substages:
- Females carry out oviposition into the plant tissue (stems, leaves, flowers), where, at an optimal temperature, in about 3 days they pass into the first stage of the larva. The optimal temperature is considered to be +23 — +26 the lower the temperature, the longer the egg stage lasts. In a month, a female flower thrips is able to lay 250-350 eggs
- The larva immediately begins to use the plant as a food base, eating juices, weakening and damaging it.
The first stage of the larva of thrips is characterized by a light, almost transparent shade, which over time transforms into yellow in different shades and degrees of brightness, characteristic of adults. The development of the first larval stage lasts 1-2 under optimal climatic conditions.
The second stage of the larva is characterized by the yellow colour of the body and a large size. The transition time to the pupal stage is approximately 4-5 days.
The pupa is divided into two substages — the pronymph and the nymph. Thrips spends these stages in the ground, and up to three days pass before the appearance of an adult.
Imago is an adult individual of the Western flower thrips immediately begins to feed and reproduce after its appearance. In greenhouse conditions, the process of development and reproduction is continuous.
The damage caused
Western flower thrips feeds on the plant, piercing its tissues and consuming cellular juices. This leads to a violation of the integrity of internal processes, weakens photosynthesis, transpiration and generally destroys the plant. The activity of the parasite occurs at the larval and imago stages, but given the rate of reproduction of the species, we get a continuous process. While some individuals are in the pupal stage, others are in the larval stage or are already adults. In addition to these, so, destructive factors, Western flower thrips tolerates tospoviruses of tomato bronzing and necrotic spotting of balsam. It also feeds on pollen, which can lead to underdevelopment of flowers.
Detection methods
Dead tissues in the form of necrotic formations can be found on the leaves. The surface becomes rough, holes form on it, as a result of which the foliage dries up and falls off. The curvature of the stem is detected, as well as its blackening. The presence of thrips can be expressed in the appearance of light gray areas on the plant.
Means of struggle
When detecting the Western flower thrips, quarantine measures must first be applied — to destroy infected plants, sterilize inventory, disinfect the soil and monitor weeds.
Among the chemical means of protection against thrips, a fairly wide range of drugs is presented. However, do not forget about the insect’s resistance to existing and rapid adaptation to new ones, as well as about the stages of development in which flower thrips are not subject to chemistry in connection with the habitat. First, attention should be paid to control and prevention.
Biological means of protection effectively help in pest control. Every year such measures become more and more popular. The natural opponents of the Western flower thrips are predatory bugs Orius and predatory mites Amblyseius. Among the predatory bugs can be distinguished — Orius laevigatus, Orius majusculus and Orius niger. These are effective on a wide range of crops against thrips at all stages of development. Among predatory mites, Amblyseius swirskii and Amblyseius cucumeris stand out. Amblyseius are effective against the larval stage of thrips, but in parallel they destroy the younger stages of whitefly.