It is often mentioned that a way to control spider mites is to increase the moisture in the growing environment. Does this method work as a result of the mites dying from an inhospitable environment or from them (or their eggs) going into hibernation to wait for more favorable conditions?
I have always been under the impression that high humidity creates an unfavorable environment but... never looked any deeper. So, I dunno, I am curious to see if you get a good answer.
Hi Junglekeeper: I am more interested in the question you did not ask should it relate to a specific plant. Years ago I learned Mites and Spider Mites to be two separate, and distinctly different insects. Today, both insects seem to be lumped together almost as one insect for control purposes and I feel that is a mistake but perhaps I am missing something. I think a lot depends on which form of Spider Mite are we talking about in regards to whether humidity can be a deterrent. Spider Mites on Strawberries hide on the undersides of the leaves and will congregate near the clump whereby the Spider Mites are locating themselves in the more humid parts of the plant. Spider Mites on certain Conifers will be found on the underside of needles far away from the trunk, whereas Spider Mites on a Cryptomeria elegans 'Nana' will primarily be located in the driest possible areas nearest the trunk. On Cotton and Almonds our Red Mite is more of a dust Mite. Whereas, Citrus Red Mite certainly is not a dust Mite by any means. In Fruit Trees I was astonished to see that the Pacific two spotted Mite is now considered to be a Spider Mite by various Universities. I think with the above plants mentioned, that humidity is not necessarily a factor for a cultural control for this insect. The reason why I like overhead watering for many trees and specific crops that can be affected by Mites and Spider Mites is that we like to wash them off the leaves if we can. Forcing a liberation of the insects into the air here makes them susceptible to our heat of which many of them will simply burn up. We also in part are thinking of liberation to make them exposed and easier for attack by their natural enemies. Anything we can do without spraying the crop or trees will help us in our attempts to prevent the insects from laying eggs and regenerating themselves. I know many a Cotton grower that when the Red Mite comes in late in the growing season that they will go ahead and spray their defoliants a little early rather than use a Miticide on their Cotton. Increased humidity itself is not a suppressant for these insects. Granted, we are more likely to see these insects in drier climates but Spider Mites, for example, can and have shown the ability to live quite well in cool, wet climates. One of the more irritating pests on Conifers in the Pacific Northwest are Spider Mites. Jim
In this case we're dealing with mites on indoor plants. I believe there may have been a mix of both black and red mites on different plants. The infestation was in its early stages so I sprayed the infected plants with insecticidal soap followed by a thorough hosing down. Stragglers will be dealt with by spot application of the soap spray.
Hi Junglekeeper: Well, I know what it was like for me to get rid of Spider Mites that came into our home on one Orchid I bought for the misses. Indoor control is a real pain as the humidity inside a home or a greenhouse works against us. I am not so sure an insecticidal soap will work for you indoors. Outdoors the soap will be much more effective. The soap itself does not necessarily kill the Spider Mites but does disrupt them enough to prevent them from laying their eggs. For our Miltonias, Oncidiums, Oncidium hybrids and Dendrobium Orchids I had to use a low grade organo-phosphate to do the job for me. The Cymbidiums and Cattleyas were not affected by the out break, yet I had to spray them also. I sprayed all of the plants outdoors more than once, about 3 times, let them dry off and brought them back indoors. I used a Malathion-Diazinon mixture. The problem plant for us was not so much the Orchids, the Spider Mites seemed to love our Anthuriums much better than they did the Orchids. Jim
