In a recent research paper from Wageningen entitled:  Effect van zwavel op natuurlijke vijanden, the authors (Juliette Pijnakker, Pierre Ramakers, Ada Leman, Cécile Added, Laxmi Kok & Eric De Groot) outline some things to consider when using sulphur and biocontrols in the same greenhouse:

• The Sulphur vapour is extremely harmful to the adult gal midges (Aphidoletes, Feltiella) and they stop functioning (working).


• The sulphur that settles on the foliage stopped the development of the midges' larva.


• The sulphur layer on the foliage of 1 night of use of the vapourizers (8 hours) kills 50% of Encarsia formosa. After 3 nights of 8 hours this is 90%.


• The effects of the sulphur layer on the foliage only had minimal effects on the older (adult) predatory mites. The distance of the sulphur pot did not effect this outcome.


• The effects of the sulphur vapour and sulphur build up on the foliage: after 3 nights of sulphur use at 8 hours per night, the predatory mites hardly lay any eggs on the 4th day.


• Decreasing the sulphur use to 4 hours per night did not improve this outcome.


• Measuring the amount of sulphur build up on the foliage was not correlated to the amount of sulphur vapourizers per Ha.

The report (in Dutch) can be accessed by contacting Jamie Aalbers (jamie@fco.on.ca)