The questions and observations on fogging by Mr. Sparrow are worth consideration. Yet, there is an additional quandry involved to resolve regarding pest management. Fogging is eminently satisfactory to all the standard and significant pest problems on orchids, the critters appreciate the fogging, but most of the problems can be reduced by applying water appropriately in the greenhouse.
A classic example is spider mite, or red mite to some. In addition to excessive use of insecticides fogging does wonders for enhancing mite populations (and favors aphids, scales, mealybugs, snails, sowbugs, millipedes, etc.). The mist increases the ambient humidity, increases the leaf surface humidity, falls gently upon the leaf, condenses upon upper leaf surfaces and flows off, yet does not directly hit or flow over lower leaf surfaces - all factors which make mites happy. [Sorry for the anthropomorphism!] Indeed, misting and spraying lowers ambient temperature, but that is rather temporary and rather insignificant to the mites. To help keep mites under control use a spray system that produces water drops that will impact the plants with some force, that is, mimic rain. The mites must be forceably knocked about by the water drops, not rampantly knocked-up while enjoying the conditions provided to them. However, it you own stock in DuPont, Monsanto, or any of the other environment modification corporations, then spray away and use a fogger. New plants can always be purchased. BTW, don't forget the non-orchids, they are often the main source of pest infestations on the orchids. Paul On Mar 21, 2006, at 5:52 AM, Oliver Sparrow wrote: > > There has been a wealth of good advice on foggers, but > fundamentally, why fog > at all? Few wild orchids get fogged regularly, except by way of > morning dew > which is delivered by fog. What intense, daytime fogging does > provoke is > leaf-covering algae, slime on glass and black gunk on the floor. I > used to > have a compressor and pump driven system which was aimed at one > class of > tropicals, but it was a pain to maintain - draining the compressor > weekly, > which meant disassembling the entire sound buffering system, for > example - and > it did not seem to deliver much by way of improved cultivation. > > What orchids need, I suggest, is "rain" at the right temperature, in > quantities which reflect the amount of evaporation to which they > have been > subjected. I do in fact use roof mounted light sprays (mains > pressure) to > humidify when cooling fans are on in summer, and - whre plants are > not being > held dormant - to offset the drying that occurs in glass houses in > the winter. > Cold walls make for condensation, and water quickly transfers from > anything > damp to the glass under such conditions. I do not wet the plants, > but try to > keep the humidity up with water troughs and occasional bursts of > spray. > > The modification which has made a huge difference is to put a water > heater in > line with the spray feed, such that the incoming water (and hosed > water, when > used) is always as 22C. As one is anyway heating the water - one > way or the > other! - when it is introduced to the glass house, this is not an > issue of > economics so much as an added complication to manage. > ______________________________ > > Oliver Sparrow > +44 (0)20 7736 9716 > www.chforum.org > > > _______________________________________________ > the OrchidGuide Digest (OGD) > [email protected] > http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com _______________________________________________ the OrchidGuide Digest (OGD) [email protected] http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
