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Klem's Greenhouse Inc.

Rieger Begonias since 1985

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Powdery Mildew Control






Every once in a while someone discovers the perfect solution to one of my difficult greenhouse problems.  Vaporizing Sulfur has been that perfect solution for our Powdery mildew problem on Begonias.  The only time we have seen powdery mildew in the last 6 years was one time when we forgot to fill the vaporizers.  They have worked in our roof vented Dynaglass houses as well as a double poly ground to ground house with a unit heater and fan-jet.  I don’t know if it works for other crops but if I had a powdery mildew problem on something else I would certainly give it a try.




The vaporizers are small hot plate units that come ready to hang and plug in.  Steuber Distributing and the Fred C. Gloeckner Co. both sell them ($65-$80.00 ea.).  We have one vaporizer for every 1200 square feet (12,000 cubic feet) and place them so that the fan-jets or HAF fans will evenly distribute the vapor.  The vaporizers are plugged into outlets that run through a 24 hr time clock set to run every night from to .  We purchased our sulfur vaporizers about 7 years ago and we haven’t had to replace one yet.




Using 99.9% pure sulfur flakes is very important.  97% pure spray sulfur will not work.  We just refill the cup once a month and let them do their thing.  My 3-year supply of sulfur for 20,000 sq. ft. cost me $5.75. 




I don’t know whether the sulfur has any lasting effect once the plants leave the greenhouse.   This is because the second part of our powdery mildew program is one application of the fungicide “Strike” before shipping.  Strike protects the Begonias from mildew for 2-3 months and has turned what used to be our biggest customer concern into a rare problem.