I am a tubestock grower of grevilleas by cutting. Whitefly has been a
constant problem. In the past I have used a systemic insecticide to control
them but am desperate to find an alternative.
I have used parasitic wasps and sticky traps in the past but this does not
prevent sudden outbreaks in the hot house. The hothouse conditions are ideal
for rapid population increase of whitefly.
What I am looking for is a safe environmentally friendly method to treat
cutting material before putting them in the hot house. I need something to
kill the egg and larval stages. I could easily dunk all cuttings but what in?
I use very young soft growth to strike from and so must be careful not to
suffocate or burn the cuttings.
Any ideas you may have would be greatly appreciated.
Using parastitic wasps is still the best option. Dipping the cuttings in pesticides will not help, but the parasitic wasp, Encarsia, does have a proven track record, world over. In keeping with the holistic principle of organic growing, it is better to look at ways of improving management practices before turning to organically acceptable sprays - because even these can have detrimental effects. To get the best out of the Encarsia wasp, introduce it at the first sign of a problem - the wasp usually takes several weeks to start their reproductive cycle, so early release is important. A good strategy to keep the wasp reproducing at their optimum is to keep the hothouse at between 23-27 degrees celcius. Keep humidity low and the light levels low. Good luck!