Jun 072018
 

Photo by John Tann. Sourced from Wikipedia

It is the larval stage of these small flying insects that create the most havoc, but their numbers can build up to such a level that the flying gnat itself creates an unpleasant nuisance in the house. Small dark bodies with long legs and a single pair of wings, these small flying insects commonly live around a week before dying en masse, usually on your sunny windowsill just before your mother in law comes to visit.

The gnats lay their eggs (100-300 per female) in the soil. Once they hatch, the larvae feed for 8-14 days on root hairs, feeder roots, organic material, fungal material and even the tender lower stems of the pot plants. It is this stage that causes damage: sudden wilting, poor growth, loss of vigour, yellowing and leaf drop. After 1 to 2 weeks the larvae pupate for 7 days and then hatch into the adult flying gnats. Total life cycle is around 3-4 weeks.

Control

Gnats-a-Go-Go – Will be available in the nursery from mid August 2020

Fungal gnats are from the Sciaridae family of flies and are the bane of indoor plants enthusiasts. Finally we have found a simple and effective answer. Prior to this we recommended a great nematode, which worked really well, but only had a two week shelf life, so we had to take orders in advance and it was a bit of a pain.  Now there is a product which is equally effective but easier to manage, having a 2 year shelf life. Gnats-a-Go-Go is a water soluble granulated powder of a naturally occurring biological control agent (Bacillus thuringiensis subsp. Israelensis, Bti) specific to the Sciaridae family. Gnats a-Go-Go specifically targets fungus gnat larvae from first to fourth instar stage.

Gnats a-Go-Go targets the in-soil stages of the life cycle, so you water the solution into the soil.  A single application is generally sufficient for light infestations, or just as a preventative treatment when you bring a new plant home.  Heavier infestations may need 2 to 3 treatments, 7 -10 days apart. Heavier infestations (and they can get really bad…) will need a stronger solution (more Bti to consume the greater number of larvae in the soil).

Mix rate: Infestation level – light/preventative (1g/L), medium (2g/L), heavy (5g/L).

Agitate the solution to keep the Bti evenly suspended. Use all the solution – do not store for later use. Store Gnats a-Go-Go in a dark place to prevent degradation from UV exposure.

Finally – a good workable long term solution, such a relief. Available in the nursery in 50g, 100g and 200g packets.