It is possible to protect your roots from fungus gnats or black flies biologically while still spraying plant foliage for other pests.
Fungus gnats or black flies can be a difficult pest to manage in a cucumber growing system, however you are able to manage this pest easily with the introduction of the predatory mite Hypoaspis from Bio Works. Normal spray applications can be made to the plants without interfereing with the Hypoaspis fungus gnat predators provided the pots are not drenched with chemical.
How it works?
Hypoaspis miles is a soil inhabiting predatory mite that preys on insects within the top layers off media/soil. Hypoaspis eat the eggs and early stages of fungus gnats thus preventing the establishment of large numbers of adult flies. They can even feed on algai and fungi to maintain themselves. Early application of the mites is critical so as to prevent a build up of fungus gnats through the crop cycle. Generally one application about 1 week after plant emergence is recommended at a rate of a 2 litre bucket (30000 mites) per 1000 plants. The Hypoaspis arrive blended through a mix of coccopeat and vermiculite, about a teaspoon needs to be added to each pot, the predatory mites then establish themselves in the pot and experience has shown that they will last the life off the crop.
Fungus gnats can also transfer disease from pot to pot plant to plant, ensuring fungus gnats are effectively controlled along with clean water will drastically reduce the incidence of root diseases such as pythium, phytophoria and fusarium.