Tetrastichus diplosis

Tetrastichus diplosis is a specialized hymenopteran parasitoid that is often considered in agronomic practice within the context of regulating midge populations. Systematically, it belongs to the order Hymenoptera, family Eulophidae. Although many members of this family are beneficial entomophages, this particular species plays a complex role in the agroecosystem.

The primary host associated with this species is the sorghum midge (Stenodiplosis sorghicola). The parasitoid attacks midge larvae developing inside the ovaries of cereal crops, particularly sorghum. Thus, its damage can manifest indirectly: by suppressing the primary parasites of the midge, it reduces the natural control of the pest population, thereby contributing to the increase in phytophage numbers.

The life cycle of Tetrastichus diplosis is closely synchronized with the phenology of its host. The female lays eggs directly into the midge larvae residing inside the sorghum spikelets. The development of the parasitoid larva occurs within the host's body, culminating in pupation and the emergence of adults. The rate of generation depends directly on the temperature and humidity conditions during the flowering period of the cereals.

The nature of the damage caused indirectly by this species is the disruption of the natural regulation of the sorghum midge population. As a result of the parasitoid's activity, the number of surviving midges increases, leading to mass grain underdevelopment, floret sterility, and a significant reduction in grain sorghum yields. Plants may not show specific visual signs of damage, other than the absence of fully developed grains in the panicles.

Protection measures include a comprehensive approach aimed at limiting the reproduction of the sorghum midge as the primary pest:

• Strict adherence to crop rotation to break the pest's development cycle.
• Elimination of wild grasses that serve as reservoirs for the midge.
• Selection of sorghum varieties with tight glumes that prevent oviposition.
• Application of authorized insecticides during the peak flight period of the midge adults.