[Xardas Damon]

Hi everyone,

I have a problem with mold in my cultures especially with Hydei fruitflies. So far I always threw away cultures that showed signs of mold but after reading some older posts in this forum apparently mold isn't an issue for the frogs but might outcompete my flies.
Is this still true?

I culture my flies in a medium made out of the following (for 4 cups):
-125 gr of oatmeal

• 350 gr of apple sauce
• 50 mL of apple cider vinegar
• 1 EL of sugar
• 3 EL of brewers yeast

Last time I tried adding a pinch of cinnamon to the mixture because I read it helps fighting the mold but to no avail.

 

[JasonE]

Mold isn't that big of a deal but it's not what you want. Try using white vinegar along with water when you make cultures.

 

[Chris S]

Or mix them a bit drier, see if that helps too.

 

[Xardas Damon]

Mold isn't that big of a deal but it's not what you want. Try using white vinegar along with water when you make cultures.

Thats good to here. I don't want to start from scratch every time my Hydei start molding. With melanogaster I had better results, but maybe next time I will try replacing the Apple Cider vinegar with white vinegar and see if that solves the issue for me.
The guy I got the recipe from said, that he usually only experiences mold when the new culture has too little flies in it, but I really don't think thats an issue here.

 

[Xardas Damon]

Or mix them a bit drier, see if that helps too.

So maybe adding more oatmeal/less apple sauce? I guess I have to do some experimenting on my media. I was thinking about adding more sugar, so that the yeast can develop faster.

 

[Ed]

Generally the mold seen in the cultures can easily grow at pHs below what the flies can easily tolerate so the use of vinegar is more of a placebo effect (aka voodoo husbandry). A similar case occurs with the use of cinnamon since at levels that inhibit molds it is well past the amount required to kill the flies.
The issue is that you lack mold inhibitors that are available in premixed commercial diets, the simplest solution is to just use one of them, the Carolina Biological Supply media is cheap and grows flies just fine and you can even mix it 50/50 with home made media and still get inhibition of mold growth (search Carolina recipe in the forums).
You will need a new supply of flies as the ones in the contaminated cultures will transport the mold to new cultures and in cases like that the yeast isn't going to inhibit the mold.
With all of that said why are you using a media that is substandard for providing needed nutrients to the frogs? It lacks carotenoids which have been shown to benefit the frogs?

Some comments

Ed

 

[Socratic Monologue]

Generally the mold seen in the cultures can easily grow at pHs below what the flies can easily tolerate so the use of vinegar is more of a placebo effect (aka voodoo husbandry). A similar case occurs with the use of cinnamon since at levels that inhibit molds it is well past the amount required to kill the flies.

Are there any data or studies that we could look to to learn more about this? I'd be interested, but the only insect toxicology studies I could find were involving cinnamon oil (which we don't use) and wood vinegar (which is quite different from just diluted acetic acid or ACV).

I don't know the tolerance of yeast vs multicellular molds for cinnamon, but using cinnamon in bread making is very enlightening regarding its antifungal properties -- about 0.5% by total dough weight inhibits yeast noticeably. Here's a study showing that that same concentration of cinnamon can be prepared to substantially inhibit tomato plant fungus. That concentration is about, very roughly, 1/3 tsp (a gram) cinnamon in a normal (200g total weight, I estimate: 1/2 cup of water and about half that of media by weight) culture.

Again regarding yeast, but ACV begins to inhibit Candida at 2.5mg/ml solution, so 0.3ml in a half cup of water used for a cx. Browsing studies suggests that there's thought to be more going on than just pH effects.

I wouldn't claim that ACV and vinegar would be as practically effective as something like methyl paraben, but they're not obviously voodoo. Thanks for any links you might have.

 

[Chris S]

So maybe adding more oatmeal/less apple sauce? I guess I have to do some experimenting on my media. I was thinking about adding more sugar, so that the yeast can develop faster.

Play around with some different mixes if you want.

I would recommend looking at Ed's comment above. Some of these commercial premixes are just far superior. I use Repashy, and it really isn't that expensive when it comes down to it and have had great success with it.

 

[Ed]

Are there any data or studies that we could look to to learn more about this? I'd be interested, but the only insect toxicology studies I could find were involving cinnamon oil (which we don't use) and wood vinegar (which is quite different from just diluted acetic acid or ACV).

You just had me digging back into the archives of Dendroboard looking for the original post from @2008, yes the studies use the oils from cinnamon but you can also calculate out the amount of cinnamon required to supply that concentration of oils. It was one of the occasions where I unfortunately didn't post the math but the values for the oil working as a antifungal came from Bullerman, L. B., F. Y. Lieu, and Sally A. Seier. "Inhibition of growth and aflatoxin production by cinnamon and clove oils. Cinnamic aldehyde and eugenol." Journal of Food Science 42.4 (1977): 1107-1109.

If remember correctly this is the reference from where I got the ld50 values I extrapolated for toxicity of the flies,
Mondal, Mina. "Toxicity of essential oils against red flour beetle, Tribolium castaneum (Herbst)(Coleoptera: Tenebrionidae)." Journal of Bio-Science 14 (2006): 43-48.
The two groups of molds we tend to see most frequently are Aspergillus niger and Penicillin sp of which A. niger as part of it's colonization of the culture acidifies the media potentially down below a pH of 2 which is below the threshold of survival for fruit flies.
See Andersen, Mikael R., Linda Lehmann, and Jens Nielsen. "Systemic analysis of the response of Aspergillus niger to ambient pH." Genome biology 10.5 (2009): 1-14.
As for the protection from fungal growth from the acetate that depends on the strain as some strains of A. niger can use acetate as a nutrient while others show inhibition or poor growth.
Low pH can also have a negative effect on the flies (I no longer have access so going off memory)
The Effect of Resource pH on Pupation Height in Drosophila (Diptera: Drosophilidae)
Journal of Insect Behavior, 1998, Volume 11, Number


If I have to I can repeat the process for Penicillium and try to recreate my thoughts from 2008 but it might have to wait for a day I feel better and that I no longer have access to many papers and journals.

As for baking and yeast, yes cinnamon is frequently used but the solidity of bread dough is very different structurally than the fly cultures. Think about the structure of bread particularly once it has developed the targeted amount of gluten versus the cultures... Cultures are much more fluid whole the goal of the gluten is to create a structure that retains CO2...

Some comments

Ed

 

[Carl999]

Not a German supplier, but Josh's Frogs sells methyl paraben:

Methyl Paraben (1 lb / 453 grams) | Josh's Frogs

Methyl Paraben (1 lb / 453 grams) is a fantastic mold inhibitor for use in fruit fly cultures. Josh's Frogs only sells pure, quality methyl paraben at low cost.

www.joshsfrogs.com

Another suggestion I've read. Before seeding a new culture, put it in the microwave for a few minutes, medium and all. At least that enables you to get off to a sterile start.

 

[Xardas Damon]

I assume that the mold probably is also transferred from old to new cultures. I guess I will try out a media to see if it really works that much better like you people suggest. Although I will have to figure out where to best get it in Germany.
I just really liked the appeal of a "natural" media with stuff I have in the house most of the time anyway. Guess I will have to get a horse to get rid of the remaining Yeast if the media will work out better in the long run (as I would assume).
Thanks for all the replies.