Using a soap based spray kills the pests by dehydrating them. It also makes them cleaner and more appealing to the predator insects. Just kidding. Soap dehydrates. The question is how much soap do you use and what kind of soap do you use? There is hand soap and detergent soap. This recipe is based on dish washing soap or detergent soap such as Ivory or Dawn.
I have read 1 tablespoon per quart and 1 tablespoon per gallon. I have read up to 4 or 5 tablespoons per gallon and up to 12 drops per gallon. My recipe is based on what works for me. The general word is that 1% to 2% soap concentration as a total percentage of volume works best. Keep in mind 1% to 2% per quart is less than 1% to 2% per gallon, soap addition. Same percentage but more soap is needed in more water to maintain the percentage.
I also suggest you spray a few leaves of each vegetable plant to see if this formula recipe burns the plants you want to spray. You should know in about 3 days if it damages them. This is a good rule for any homemade spray you may use.
I also suggest making this in a gallon milk container. I would provide a quart recipe but who the heck can tend to a good size garden with a quart. You can always pour it into a quart spray bottle if needed. I typically make this directly in my sprayer container. This spray does not go bad. You can store it in the gallon milk container too.
Insecticidal Soap Spray: The Basic Recipe
2 tablespoons of detergent dish soap like Ivory or Dawn
1 gallon of water
Combine ingredients in a milk container and shake well. Transfer it to a spray bottle or larger sprayer as needed.
Some people have added vegetable oil, garlic, Tabasco and other ingredients to up the bang of the spray. I haven’t tried adding things. The soap is what dehydrates the pests.
Pest that are killed by this spray include small ants, aphids, fruit flies, leaf hoppers, spider mites, whiteflies and other soft bodied insects. Caterpillars aren’t really affected by soap.
I have also read it may help with diseases such as leaf spot, powdery mildew and rust.
You need to spray the insects for soap to work. Make sure you spray the tops and bottoms of the leaves. It is recommended you spray in the morning or the evening. Direct sunlight my increase the chances of burning your plants. I spray when I have the time and have not had any problems in my zone.
The soap does act almost immediately once it hits the insect. If you wish, you can rinse down your plants about 1 hour after spraying if you are concerned about leaf burn. Remember to test it out on some leave first before dowsing your entire garden.
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