Flower drop probable causes:
1. Day temp too high >95F
2. Night temp too low <65F or too high >85F
3. Too much nitrogen fertilizer
4. Too much water
5. Low light levels (reduces fertility).
6. Very low humidity (reduces fertility)
7. Poor air circulation (air circulation contributes to...
In the Bajío of México, chiles are grown with hardly any human intervention (fertilization) at all.
The campesinos plant them and forget them til they pick the fruit for market. Seem to do pretty well.
IMG_2107 by Willard Bridgham, on Flickr