The development cycle of thrips comprises 6 stages (figure 1): egg, two larval stages, two pronymph stages and adult (figure 6). The length of the cycle varies depending on the temperature and the host plant; by way of example, for F. occidentalis it fluctuates from 34 days at 15 ° C to 13 days at 30 ° C.

• Forms of conservation and / or alternative hosts

It is the larvae and adults, who have taken refuge in places with mild temperatures, which ensure the sustainability of these insects. For this, they settle in the plant debris, the frames of the shelters ; they sometimes bury themselves up to 8 centimeters deep. They can also hibernate on field crops, especially on various Alliums .

• Stages of development

The eggs kidney-shaped (Figure 6-1) are deposited on the aerial organs, especially the leaves of tomato. Once formed, the larvae (figures 6-2 and 3) (figure 2), which are very mobile, will feed on the underside of the leaves. At the end of the second larval instar (Figure 6-3), they drop to the ground and pupate. The first pronymph stage (Figure 6-4) is characterized by the appearance of wing outlines. The clearer second stage pronymphatic (Figure 6-5) also shows larger wing outlines and long antennae curving towards the rear of the body. The adult (Figure 6-6) (Figure 3) have 2 well-developed wings pairs.

T. tabaci and F. occidentalis (Figure 3) are morphologically quite comparable. Only an observation of adults using a microscope can differentiate them. Their reproduction may be different depending on the species. It is asexual in T. tabaci, unfertilized females giving birth only to females (parthenogenesis). In F. occidentalis , it can be sexual or asexual, unfertilized females giving birth only to males while those which are fertilized give birth to females.

Thrips feed by sucking the contents of cells in the epidermis. Damaged tissue quickly necroses.

• Dispersion in culture

Thrips are fairly easily dispersed in crops, passively swept away by drafts and / or actively flying. Workers can contribute to it during cropping operations. These insects can be dispersed by plants or plants of other parasitized species.

• Favorable development conditions

The nature of the plant, the temperature, the humidity in the crop, notably influence the development of thrips.

Last change : 07/08/21