Not mine but from another forum originally:
Knock Off Nuke 'em:
Screw’Em - Insecticide and Fungicide
(Against aphids such as spider mites, broad- and russet mites, thrips, whitefly etc. Also prevents mould, fungus and powdery mildew. Safe, non-toxic, can also be used on buds and can also prevent mould on buds after harvest)
INGREDIENTS
Insecticidal Soap (also called Potassium Soap) (10-20ml)
Distilled Water (1L)
Yeast (fresh brewery yeast or dry yeast) (20g)
Lemon Juice (8.5ml)
Potassium Sorbate (500mg)
Sodium Benzoate (500mg)
I am using Insecticidal Soap for a long time for spraying, I assume the added ingredients in Nuke ‘Em are to give the spray more oomph. The Lemon Juice, the Potassium Sorbate and the Sodium Benzoate are preservatives for the solution but they also prevent mold, fungus, powdery mildew etc. which IMO insecticidal soap alone can’t do. There may also be other insecticidal effects from these ingredients. The Yeast is possibly added so that bugs which are not instantly killed are eating the stuff so that the spray has a double-effect, which may be needed for some more difficult critters like broad mites.
I established the percentages based on the label for Nuke’Em and other info I found on the web, eg. what a typical percentage for Potassium Sorbate etc. is…so this may not be 100% accurate like in the original, but it should do.
INSTRUCTIONS
Make 1L of insecticidal soap solution according to instructions for your insecticidal soap. (Typical is 10-20ml insecticidal soap for 1L water). (I use distilled water since with water from the tap the soap can sometimes form suds and flake)
Add 8.5ml of Lemon Juice. Lemon Juice contains 5-6% of citric acid, so this comes to 0.05% of citric acid for 1L solution. You could also use citric acid directly, but why bother as everyone really has lemon juice.
Dissolve yeast in the solution. I have no information about the exact amount of yeast to use, but I would add about 20g. Reason being that the yeast comes before the “Soap” (respective “potassium salts of fatty acids”) in the ingredient list for Nuke’Em. As we know we should use 10-20g of soap, take about the same amount or a little more of Yeast.
Add 500mg of Sodium Benzoate
Add 500mg of Potassium Sorbate
NOTES
If you want to make larger batches: Above is for 1L. 1 gal = 3.785L.
As this contains preservatives, it should be possible to make this spray and store for some time.
Use a good garden sprayer for spraying. A manual garden pressure sprayer is much better than these dinky hand sprayers. If you don’t have a pressure sprayer, trust me the $15 or whatever they cost is well worth it.
Use the usual precautions, like not spraying in direct sun, spray either at night before lights off or even better early in the morning. Spray your plants well, also the underside of the leaves. I am using insecticidal soap against aphids etc. for a long time and it has never in any way, harmed the plants. The list of ingredients for this DIY looks safe to me, and should also be safe on buds, unlike eg. Neem which would give your buds an awful taste. This DIY spray should also be good not only for aphids but also for mould, fungus, powdery mildew etc.
Try it and let us know! These ingredients, if you already have the insecticidal soap should only cost a few bucks, and this should be good for making tons of this stuff that should last you for a long time.
. After emptying my tent, I washed it thoroughly with water and bleach with soap. Then I used a vapour cleaning machine and boiled the remnant eggs, vapour reaches everywhere. Started a new grow with yellow and blue sticky traps and so far so good, just three fungus gnats … 
