Strombocactus Carnage or: How I Opened the Bag and Let in Death by Sciarid Fly

Until lately my Strombocactus disciformis ssp. esperanzae seedlings were thriving and slowly growing in the safe and secluded environment of a plastic bag. Recently I checked the plants and found dried husks and seedlings without roots.


Strombocactus disciformis remains

When I opened the bag a couple of sciarid flies soared out. The soil was sterilized before use so I expect the flies must have entered one of the times I aired the bag.


Sciarid fly (fungus gnat)

Sciarid flies as such are not dangerous to the plant but their larvae will feed on root hairs, enter the roots or even attack the crown or stem of the plant. In the future I’ll take heed when airing my seedling bags and avoid organic material in the soil (the larvae of most species are scavengers, primarily feeding on decaying organic matter).

Today only one seedling is still alive and it is not doing well – the few seedlings surviving the attack also had to cope with the abrupt introduction to the harsh environment outside the bag (the soil had to dry out completely to kill off any remaining larvae).