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Information on Mites in Fruit Fly Cultures

As I mention in my instructional sheets on culturing flightless fruit flies, mites are a serious pest that can totally wipe out a fruit fly culturing program. Once they have gained the upper hand, they can be very hard to eliminate, even after all affected cultures are pitched, and new cultures are brought in. I say this from experience!

So, in this sheet we will discuss how outbreaks of mites can be prevented, and then we will discuss what to do if you find them. First, some general information on the mites. Mites are tiny arthropods, like ticks, and there are many different species of them. All the mites which I am familiar with, suck juices from various hosts, including plants, insects, reptiles and mammals. Some mites are able to live off of various different hosts, and some are specific to certain hosts. I do not know what species of mites will infest fruit fly cultures, but it seems likely that there are more than one species. Based on our observations here, the mites which affect fruit flies will also be found in association with domestic crickets when cultured for reptile food. These mites are small, and white or off white. When they are adult size, they are easily visible with the naked eye, and appear as tiny white specks on the sides of the fly culture….usually the insides, but in some cases on the outside of the cup as well. When the mites are on the outside of the culture, the cup will feel like it has some fine dust or sand on it. When you find a white speck on the inside of the culture, look closely at it and watch it. It should be moving very slowly. If its not moving, its either dead or its not a mite. If you are not sure if its moving, you can put a circle around it with a magic marker and then see if it has moved an hour or so later. Use of a magnifying glass will allow you to see more clearly, and with a magnifying glass you should be able to see the legs and identify the fact that it is a small creature moving around.

Ok, well next step, let’s talk about how you can avoid these little guys getting established in your cultures. Mites are “everywhere” it seems, and some low level of them may be present in cultures. I’ve had people who have worked with flies for a long time tell me that mites are always there, but that you just don’t see them or their effects unless they “bloom”. I don’t know if that’s true or not, I try to maintain a “no mites” policy with my cultures here. We spend time before each new batch of flies is made scanning the batch of flies we are going to use to make the new cultures, looking for any signs of mites. If mites are found, we do not use that batch of flies to make new ones with. Generally speaking we don’t find any mites in our cultures. Probably the number one tip for preventing mites in your cultures is to always make cultures from the newest culture you can. As soon as possible after your latest batch of cultures begins producing, make new cultures with those flies. Mites seem to have a longer life cycle than the flies do, so if there is a mite or a few in your freshly producing culture, that you are using to make new cultures, and it gets into the new culture, its going to lay eggs as soon as it can. However, due to the fact that the flies are able to reproduce and produce their next generation of flies, before the mites are, you will get a much cleaner batch of flies to make your new culture with by using the first batch of hatching flies. Using older cultures to make your new cultures with is a bad idea, and gives the mites a much better chance to get a foothold in your cultures. Once mites begin to multiply, the game is up, as they will often totally take over the cultures within a couple of generations of flies.

The second tip for preventing mites is to keep culturing materials in the freezer. I recommend you reuse those ventilated lids, but first you have to put them in the freezer for a day or so. Over night will be fine. I would (just to be safe!) put your media and excelsior in the freezer as well. Another trick is to keep your cultures on shelf paper which has been permeated with insecticide. This paper is made for lining drawers. We offer it in sheets which will accommodate 9 cultures, with no contact between the cups. Setting your cultures on the sheets without allowing them to touch each other is essential, as this prevents the mites from migrating from one culture to another. This paper is sometimes found at hardware stores or general stores.

Ok, so we have covered the steps to take to avoid mite outbreaks, but lo and behold, you have mites. Bummer! First step to getting rid of them is to pitch your cultures, and order some new ones. Before the new ones arrive, clean as much as you can around the area you have been keeping the cultures. Use a brush to get into cracks and crevices. Use bleach, in normal dilution, as it will kill most if not all mites. Alternatively use an insecticide that is labeled safe for use in the house. Something like an aerosol bug killer can be sprayed on all affected surfaces, and into the cracks. Then a day or so later clean it up if you feel this is necessary. Meanwhile you should put everything you have that is used for making your cultures, in the freezer for a day or so. I would also suggest getting the shelf paper at this point, as you will most likely have mites which have migrated into areas around your culturing area, and will come back to the cultures once they are back in the culturing area. You can also move to a new culturing area, and this isn’t a bad idea, however I still recommend the shelf paper at this point.

Hopefully this tutorial contains all the info you need to avoid or combat mites if they occur. There are chemicals on the market which can be used to rid culturing programs of mites, contact us for more on these if you cant get rid of the mites by following the steps above.