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Entomology (Study of Bugs)/Mystery mites in orchid greenhouse.

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mite on 2mm cable
mite on 2mm cable  

mite on edge of pot
mite on edge of pot  
Hi Dr. DeAngelis,

i grow orchids as a hobby and lately my greenhouse have an infestation of mystery mites, they are very tiny, white in color, with hairs and tend to crawl around the pots, bark growing media, the leaves etc..

i am not sure if they are doing any damage as they seem to be always on the move, and occasionally settling down on leaves which is abit worrying. not sure if they are the dreaded broad mite or cyclamen mite? but considering the cyclamen and broad tarsonemid mites are very dangerous, i hope they are not as it seems damage to the plants has not visible... yet!? (i hope!)

i got some  photos attached, if you look at photo 603, that black cable in comparison to the size of the mites, the cable diameter is about 2mm or 2.5mm, is that sufficient for a sense of scale?

i have more photos to upload but seems i can only upload 2 at a time, i would love to take a better shot but it seems its reached the limit of my camera's macro capabilities.

they are driving me nuts and considering my large collection of exotic orchids i would like to find out if they are harmful or not, i hope they are just some sort of mold or grain mites.

i am going to the local electronic kit shop to get a 40x to 400x USB microscope tomorrow which i hope can get me a better pic if that helps?



sincerely
Joel

Answer
Joel,

These look like mold mites, also called grain mites (see http://www.livingwithbugs.com/mold_mites.html). The mites are harmless but large numbers can elicit an allergic reaction in workers similar to dust mite allergy (in fact the two mites are closely related). Two possible sources to think about - there's either mold indicating excess moisture or these mites are often used as food for predator mites. If you have released predator mites recently these mites may have been in the mix. Again they pose no threat but if mold is excessive that could be an issue.

Jack DeAngelis

Entomology (Study of Bugs)

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Jack DeAngelis

Expertise

I can answer questions in any area of entomology (study of insects, spiders, mites, ticks, and other terrestrial arthropods). Contact me about home and garden insects, insects that bite and sting, and insects that damage homes such as carpenter ants and termites.

Experience

20 years as university extension entomologist, now retired; currently publish a website about home and garden insects.

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see www.livingwithbugs.com/resume.html

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Ph.D. in Entomology

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