Geranium seed wasp

Torymus geranii is a species of parasitic wasp belonging to the family Torymidae within the order Hymenoptera. Although many Torymus species are known as parasitoids, T. geranii is primarily recognized as a seed-infesting pest that targets specific plants within the Geranium genus.

The primary hosts for this insect are various species of wild and cultivated geraniums. The larvae feed internally on the developing seeds within the seed pods. Because they consume the seeds from the inside, the damage often goes unnoticed until the emergence holes are visible or the seed yield drops significantly.

The life cycle is closely synchronized with the flowering and fruiting phenology of the host plant. Female wasps oviposit into the developing ovaries. The larvae develop entirely within the seed capsule, consuming the embryonic tissue. Winter is typically spent in a diapause state as a mature larva inside the hardened remains of the host plant.

Infestation results in significant losses for seed producers. The damage is characterized by hollowed-out seeds that fail to germinate. Because the insect develops entirely within the protected environment of the fruit, contact insecticides are often ineffective against the larval stage, necessitating focus on other management strategies.

Effective control measures require an integrated approach. Sanitation is the most critical factor: removing and destroying infested plant material post-harvest prevents the next generation from emerging. Monitoring the flight period of adults using yellow sticky traps can help time the application of appropriate control measures to minimize further spread.